BIBLIOGRAPHY ORAS, CAROLYN DANIWES. MAY ...
BIBLIOGRAPHY
ORAS, CAROLYN DANIWES. MAY 2011. Evaluation of Plant Extracts against
Cercospora Leaf Spot (Cercospora longissima) on Lettuce. Ambiong Riverside, La Trinidad
Benguet.
Adviser: Andres A. Basalong, MSc.
ABSTRACT
The study was conducted at the Ambiong, Riverside La Trinidad Benguet from March to
May 2011. The study aimed to determine the efficacy of botanical fungicides against Cercospora
leaf spot of Iceberg lettuce.
Leaf spot symptoms on the Iceberg lettuce cultivar appeared as small yellowish spots
with brown to black dots in the center. Larger spot form from the merging of adjacent small
spots.
Results of the study showed that the plant extracts used in this experiment did not
suppress Cercospora leaf spot infection on lettuce. The plants treated with plant extracts as
botanical fungicides had infection of Cercospora leaf spot higher than the infection of untreated
plants.
1
INTRODUCTION
Lettuce (Lactuca sativa) is a native to the Mediterranean Region, where it has been
cultivated for several millennia. It probably spread into the rest of Europe during the Roman
occupation. When it was introduced into the America’s in the 15th Century, lettuce become
popular in the new world and now the major salad crop and become important in most countries.
Lettuce is unique among the major vegetables in that it is used almost exclusively as a fresh raw
product. This can be grown as a field crop or else under the protection of glass or plastic
(Snowdon, 1992).
Lettuce is a temperate annual or biennial plant of the daisy family Asteraceae or
Compositae. It is most often grown as a leaf vegetable. In many countries, it is typically eaten
cold, raw, in salads, sandwiches, hamburgers, tacos and in many other dishes. In some places,
including china, lettuce is typically eaten cooked and use of the stem is as important as use of the
leaf. It has a short stem initially, but when it gradually blooms, the stem and branches lengthens
and produces many flower heads that look like those of dandelions, but smaller. This is referred
to as bolting. When grown for food, lettuce is harvested before it bolts (Berg, 1998).
Lettuce is usually grown commonly in semi-temperate regions like Benguet. It can be
planted anytime of the year, provided that there is abundant supply of water. It is best however to
plant from September to February when climate is relatively cool (Knott and Deanon, 1967).
Lettuce growers in Benguet often observe and complain about destructive diseases of
lettuce. These diseases inflict leaf spots that lead to economic losses due to low quality of the
harvest or no harvest if severely infected.
As cited by Snowdon (1992) lettuce is a fast income generating agricultural produce,
however, pests and disease and improper postharvest handing contributes to the great losses of
Evaluation Of Plant Extracts Against Cercospora Leaf Spot (Cercospora Longissima)
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income to producers. It is a highly perishable crop that can be damaged easily due to disease
infections and adverse environmental conditions. Being a high value commercial crop, losses
through pathogen infections should be minimized. Moreover, Fry (1982) mentioned that more
than 40% of the produced is considered as loss due to over trimming, color changes and nutrition
depletion. Climate is known to be capable of causing large reduction in yield by directly
affecting the plants as well as favorably enhancing pathogens, insect and weed attacks.
Leaf spot of lettuce is one of the major diseases that often limit or reduce the production
of lettuce. Due to leaf spot infection, cleaning of outer wrapper leaves may be intense resulting to
reduction of weight, size and exposure of pale green inner leaves. Further, marketability would
also be reduced. Using non-chemical alternative control strategies against leaf spot of lettuce is
in direly important for the reason that lettuce is a salad crop. Since, potent fungicides used
against lettuce leaf spot and other pesticides for other pests would not be neutralize, because
lettuce as salad crop is not subjected to cooking.
Discovery of non-chemical products against leaf spot that is indigenous in the locality or
those that are available from other source but could that be adopted and propagated within the
locality could serve as a ready source of botanical fungicides against leaf spot. The positive
result of the study would conform to the trend of current farming that is organic agriculture.
The study was conducted to evaluate the efficacy of selected plant extracts against
Cercospora longissima.
The experiment was conducted at Ambiong, Riverside La Trinidad Benguet from March
to May 2011.
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REVIEW OF LITERATURE
Nature of Cercospora Leaf Spot
Cercospora spot (Cercospora longissima). Cercospora spot of lettuce is found
predominantly in tropical countries. The spots appear as minute water soaked brown spots, each
surrounded by a pale halo and appearing initially on the outer leaves of lettuce. The lesions may
enlarge into irregular brown areas bounded by the leaf veins and coalesce to form large blotches.
In a humid atmosphere there is a grayish to buff growth of mould giving rise to spores (conidia).
This disease may also spread to younger leaves (Snowdon, 1992). Likewise Groenewald (2006)
describe Cercospora leaf spot to initially present itself as tiny circular or oval spots on plant
leaves that enlarge with time. The spots can vary in color from dark green to brown with or
without maroon or purple margins. In later stages of the disease on the leaves or flowers may
become yellow and fall off the stems, and leaves on edible crops may become brownish-gray
color as they dry out and die completely.
Development of Cercospora leaf spot disease begins when the fungus spores are
dispersed by rain irrigation water and wind. Germination occurs in humid conditions, usually
during late spring and summer, and fungus growth is encouraged by frequently damp leaves.
Plants that measure in the fall may escape acute infection. In general, the more rain, the worse
the disease spreads. Cercospora infests seeds and crop residue where it harbors over the winter
(Groenewald, 2006).
Homer (2000) also cited that Cercospora leaf spot symptoms development is most
common on leaves but may occur on most above ground plant parts. Lesions are initially visible
on the upper leaf surface as small purple spots. The spots enlarged slightly with age up to ¼ inch
and may coalesce. The tissue in the center of the spot changes from purple to tan or gray and
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eventually become white. The margin of the spots remains purple or brown giving the lesion a
“bird’s eye “appearance. Infection sites appear as indistinct tan or bluish areas on lower leaf
surface. Symptoms expression is variable depending on the age of the leaf, susceptibility of the
cultivar or species, fungal strain and environmental conditions.
Leaf spot may reach economic threshold levels, provided young leaves and inoculum are
present, under conditions of high temperature and long period of leaf wetness. Research result
show most severe infection of young leaves to occur during periods of leaf wetness from 12 to
96 hours when temperatures fall in the range of 59-68oF or 15-20oC. This data suggest that
fungicide treatment should be applied early spring and after renovation of inoculum is present
(Ngitew, 2003).
Several species of Cercospora are responsible for the diseases on the various hosts; some
Cercospora species have Mycosphaerella as their teleomorph. The fungus produces long,
slender, color less, to dark, straight to slightly curved, multicellular conidia on short dark
conidiophores. Conidiophores arise from the plant surface in clusters through the stomata and
form conidia successively on new growing tips. Conidia are detached easily and are often blown
long distances by the wind. The fungus is favored by high temperatures and therefore is most
destructive in the summer months and in warmer climates. Most Cercospora species produce the
nonspecific toxin cercosporin, which acts as a photosensitizing agent in the plant cells; it kills
cells only in the light. The toxin incites the production of reactive atomic oxygen in the cells.
Although Cercospora spores need water to germinate and penetrate, heavy dews seem to be
sufficient for infection. The pathogen over seasons in or on the seed and as minute black stomata
in old infected leaves (Agrios, 1979).
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There are several types of lettuce, differing in leaf shape and form and in the tendency to form a
‘heart’ or ‘head’ (Berg, 1998).
Control
Cercospora disease is controlled by using disease-free seed or seed least three years old,
by which time the fungus in the seed has died; by using crop rotations with hosts not affected by
the same Cercospora species; and by spraying the plants, both in the seed bed and in the field,
with appropriate fungicides (Fry, 1982).
Other Diseases that is very common in Lettuce (Westcott, 1960)
Alternaria spot. This is caused by various species of Alternaria, has been recorded on
lettuce in several countries, on Chicory in India and on endive in Greece, on Italy and Argentina.
Endive cultivars are generally much more susceptible than Chicory to infection by Alternaria
cichorii.
Myconcentrospora spot. This has been recorded on outdoor lettuce in France and in the
UK following heavy rains and the disease also occurs in the USA. The causal fungus is
Mycocentrospore acerina. Leaf spot are circular to angular with pale brown centers and darken
margins, sometimes surrounded by a board band of grayish-green. Irregularly shaped lesions
develop on the midribs of exposed leaves. Control by fungicides sprays has been suggested.
Myrothecium rot. This is caused by Myrothecium roridum, and it has been recorded
outdoor lettuce in sprain. Warm moist weather is conductive to infection, resulting in the
formation of circular spots on both sides of the leaf blades.
Phytopthora rot. It has been recorded in Australia on lettuce as a firm dark stem rot
extending upwards into the head. The disease was found only during winter in badly drained
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fields. The causal fungus was a strain of Phytophthora porri which had an optimal growth
temperature of 15o C and failed to infect leeks on cabbages.
Phythium rot. This is caused by Phythium aphanidermatum, affects lettuce in India,
leaves in with the ground are invaded, become water soaked and decay rapidly. In the
Netherlands, species of Phythium are recorded as components of bottom rot.
Sclerotium rot. This is caused by Sclerotium rolfsii occasionally recorded on lettuce and
endive in the Southern USA. The fungus is favored by warm wet conditions and attacks leaves in
contact with the soil, giving rise to silky white mould and spherical resting bodies (sclerotia).
Plants with Antifungal Properties
Angel’s Trumpet(Brugmansia suarveolens). Angel’s Trumpet is a genus of seven species
of flowering plants in the family Solanaceae. They are known as Angel’s Trumpets sharing that
name with the closely related genus Datura. Brugmansia are long-lived, woody trees or bushes,
with pendulous not erect flowers, that have no spines on their fruit. Datura species are
herbaceous bushes with erect (not pendulous) flowers, and most have spines on their fruit
(Preissel, 2000). Brugmansia are large shrubs or small trees, reaching heights of 3-11 m, with tan
slightly rough bark. The leaves are alternate, generally large 10-30 cm long and 4-18 cm broad,
with an entire or coarsely toothed margin, and are covered with fine hairs. The name Angel’s
Trumpet refers to the large, very dramatic, pendulous trumpet-shaped flowers, 14-50 cm to 50-8
cm long and 10-35 cm across at the wide end. They are white, yellow, pink, orange or red, and
have a delicate, attractive scent with light, lemony over-tones, most noticeable in early evening.
Flowers may be single or double (Shaw, 1999). As with Datura all parts of Brugmansia are
highly toxic. The plants are sometimes ingested for recreational or Shananic intoxication as the
plant contains the tropane alkaloids scopolamine and atropine; however because the potency of
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the toxic compounds in the plant is variable the degree of intoxication is unpredictable and can
be fatal (Blanckaert, 2004).
Horsetail(Ricinus communis). Is a species of flowering plant in the spurge family,
Euphorbiaceae. It belongs to a monotypic genus, Ricinus, and subtribe, Riciniae. The evolution
of castor and its relation to other species is currently being studied. Its seed is the castor bean
which, despite its name is not a true bean. Castor is indigenous to the Southeastern
Mediterranean Basin, Eastern Africa, and India but is widespread throughout tropical regions.
Castor seed is the source of castor oil, 40% and 60% oil that is also present in lower
concentrations throughout the plant. The seeds from the castor bean plant, Ricinus communis, are
poisonous to people, animals and insects. One of the main toxic proteins is “ricin”, named by
Still Mark in 1888 when he tested the beans extract on red blood cells and saw them agglutinate.
Now we know that the agglutination was due to another toxin that was also present, called RCA
(Ricinus communis agglutinin). Poisoning by ingestion of the castor bean is due to ricin, not
RCA, because RCA does not penetrate the intestinal wall, and does not affect red blood cells
unless given intravenously. If RCA is injected into the blood, it will cause the red blood cells to
agglutinate and burst is hemolysis (Wiess, 1971).
Lantana (Lantana camara L). It consists of more than 150 species of shrubs and
herbaceous perennials, of the vervain family Verbenaceae. Lantanas are mostly natives of the
tropics and subtropics of America but some are natives of warm parts of the Old World. Their
name is an ancient one used for the quite unrelated genus Viburnum. Wild lantanas are hairy and
often prickly-stemmed. If rubbed and bruised, their leaves usually have a pungent odor. Verbena-
like flowers are formed in clusters from the leaf axils or at the ends of branches. The small berry-
like fruits contain seeds. In some regions, lantanas grow wild as weeds, chiefly spread by birds
Evaluation Of Plant Extracts Against Cercospora Leaf Spot (Cercospora Longissima)
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that are very fond of their juicy fruits. Lantana leaves can be used as a soothing agent in cases of
insect stings, skin eruptions, cuts scrapes, ulcerations, the itch of measles and chicken pox,
parasites such as scabies. However, there often conflicting reports on its use as an herbal
medicine. The green berries are toxic and there has been one human fatality attributed to them.
Animals will also be affected by eating these plants (Ferla and D’ Eeckendbrugge ,2000).
Neem tree (Azadirachta indica). As versatile as “kakawe” is the neem. In 1962, an Indian
scientist found out thaqt neem seed extract proved operative as an insect repellant. Discovery of
azadiracthan, a principal anti- feedant, was reported in 1986. Independent experiments by other
respected scientists from all over the world disclosed other neem compounds, among them
vitasinin and salanorin.
Sap from the neem tree has been tried as an insecticide and was found to destroy vicadas
and astracods infesting rice fields. Neem cake- the residue left after oil is extracted from neem
seeds- when incorporated in the soil kills nematodes.
Several experiments conducted at the International Rice Research Institute showed that
leafhoppers feed less, grow poorly and lay fewer eggs on rice plants that have been sprayed with
neem oil.
For its part, the Bureau of plant Industry of the Department of Agriculture once
experimented the effects of neem oil extract on the corn borer, the prime suspect behind the 20-
80 percent losses in domestic corn yields. The study confirms neem oil can destroy 93.3 percent
of the dreaded pest. Neem is unique among plants with pesticidal properties since it has so many
different effects on pests: It acts as a broad-spectrum repellent, insect growth regulator (it causes
deformities in the insect’s offspring) and insect poison. It discourages feeding by making plants
unpalatable to insects or suppresses the insect’s appetite (anti-feedant effect); if they still attack,
Evaluation Of Plant Extracts Against Cercospora Leaf Spot (Cercospora Longissima)
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it inhibits their ability to moult and lay eggs. Unlike most botanical insecticides, neem also has a
somewhat “systemic” effect. This means that plants can take up neem extracts through their roots
and leaves, spreading the material throughout the plant tissues (Bradley, 1992).
Sunflower (Helianthus annus L.). Are annual plants native to the Americas, those posses
a large inflorescence (flowering head). The florets inside the circular head are yellow, maroon,
orange, or other colors. The florets within circular head are called disc florets, which mature into
seeds. The florets within the sunflower’s cluster are arranged in a spiral pattern. This pattern
produces the most efficient packing of seeds within the flower head. To grow well, sunflowers
need full sun. They grow best fertile, moist; well-drained soil with a lot of mulch. The most
serious diseases of sunflower are caused by fungi. The major diseases include rust, downey
mildew,verticillum wilt, sclerotinia stalk and head rot, phoma black stem and leaf spot. The
severity of these disease effects on total crop yield might be ranked: 1) sclerotinia, 2)
verticillium, 3) rust (recently more severe), 4) phoma, and 5) downly mildew. Resistance to rust,
downy mildew, and verticillium wilt has been incorporated into improved sunflower germplasm.
The growth of sunflower as an oilseed crop has rivaled that of soybean, with both increasing
production over 6-fold since the 1930’s. Sunflower oil is generally considered a premium oil
because of its light color, high level of unsaturated fatty acids and lack of linolenic acid, bland
flavor and high smoke points (Shosteck, 1974).
Common plantain (Plantago major). Is a species of Plantago, family Plantaginaceae. It is
widely naturalized elsewhere in the world, where it is a common Plantain in some areas where it
is introduced, particularly North America. Another one of its common names was “Soldiers
Herb” for its use on the battlefield as a dressing. It is an herbaceous perennial plant with a rosette
of leaves 15-30 cm diameter. Each leaf is oval, 5-20 cm long and 4-9 cm broad, rarely up to 30
Evaluation Of Plant Extracts Against Cercospora Leaf Spot (Cercospora Longissima)
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cm long and 17 cm broad, with an acute apex and a smooth margin; there are five to nine
conspicuous veins. The flowers are small, greenish-brown with purple stamens, produced in a
dense spike 5-15 cm long on top of a stem 13-15 cm tall (Sauer, 1998).
Evaluation Of Plant Extracts Against Cercospora Leaf Spot (Cercospora Longissima)
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MATERIALS AND METHOD
Collection and Diagnosis of Diseased Specimens
Infected leaves of lettuce were collected from the experimental farm in Ambiong,
Riverside La Trinidad Benguet. The specimens gathered were sealed in paper bags and brought
to the laboratory for diagnosis to confirm the causal pathogen.
Symptomatology and Microscopic Activity
Symptomatology and microscopic observations were done and recorded. The
Microscopic examination of the structures of the pathogen from leaf samples was done to
observe the shape, size, and color of the spores and filaments.
Isolation of Pathogen
The collected diseased plants were washed with tap water to remove dirt. Five pieces at
2-3 mm2 were cut within progressively diseased portion on the leaves. The pieces of tissues were
disinfected in 10% chlorox for one minute, washed in three changes of sterile water and blot
dried on a sterile tissue paper. Five pieces of cut tissues from the leaves were planted in plated
PDA to isolate the pathogen. Colonies of the pathogen were re-isolated in test tube slants to
obtain pure culture. The pure cultures were sampled for microscopic observation to confirm the
causal pathogen of lettuce leaf spot.
Evaluation Of Plant Extracts Against Cercospora Leaf Spot (Cercospora Longissima)
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Collection and Preparation
of Botanical Fungicides
Plants evaluated for fungicidal properties were collected within Benguet, wherever it
could be found. These were processed by macerating to obtain sap extracts. Botanical plants used
were selected based on their use as medicinal plants or reported to be effective against pathogens
and insect pest. The preparation of the botanicals followed the procedure using ethanol for
extraction. For solvent extract, 30 grams of botanical plants were washed with tap water,
chopped and placed in an Erlenmeyer flask. Ethyl alcohol (95 percent) was used to soak the
plants. Tissues were macerated using the mortar and pestle. The suspensions were left to stand
for 2-3 days. The tissues were separated from the liquid portion using a filter paper. For every
0.50mg of the plants extract, 1 ml of acetone was mixed to dissolve the plant extracts.
In the water extract procedure, 20 grams of botanical plants were disinfected with chlorox
then rinsed with distilled water. Following the weight/ volume formula, 20 grams of botanical
plants were soaked in 20 ml of water.
Seedbed Preparation and
Seedling Management
A seedbed was prepared for the growing of lettuce seedlings, Iceberg variety. Three (3)
weeks after sowing, the seedlings of lettuce were transplanted in the experimental area.
All cultural practices involved in caring lettuce seedlings such as watering, replanting
damaged by cutworms, and control of insect pest were done in all the treatments. Seedlings were
not protected with fungicides from germination to transplanting up to the termination of the
experiment.
Evaluation Of Plant Extracts Against Cercospora Leaf Spot (Cercospora Longissima)
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Field Trial and Planting
The lettuce seedlings that were free from Cercospora leaf spot were transplanted in the
experimental field. The plots measured 0.80m x 5m each. Double row planting was done per
plot. Cultural practices were done regularly such as watering, weeding and hilling up. No
chemicals and inorganic fertilizer where added except for the spraying of the different plant
extracts. Treatments were replicated three times following the Randomized Complete Block
Design (RCBD).
The Treatments were:
T1- Control
T2- Angel’s Trumpet (Brugmansia suarveolens)
T3- Lantana (Lantana camara)
T4- Horsetail (Ricinus communis)
T5- Neem (Azadirachta indica)
T6- Common plantain (Plantago major)
T7- Sunflower (Helianthus annus L.)
Data Gathered were:
1. Diagnostic activity
a. Symptom description
b. Morphological Characteristics of the pathogen from the fresh plant samples and
culture media.
c. Cultural characteristics, colony (color, spread or growth and unit time)
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2. Field
a. Infection rating. The scale developed by the British Mycological Society
(Anon, 1947) was used in the study.
Rating Scale Description
1 0 No infection
2
10% Only few leaves affected, up to one spot
3 15% Nearly every plant affected
4 25% Every plant affected and about half of the leaf area destroyed
by spot
5 50% About three quarters of the leaf is destroyed by spots
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RESULTS AND DISCUSSION
Disease Symptoms
Cercospora longissima infection also called frog eyespot first appears as small yellowish
spots on the upper leaf surface. As the spots develop and enlarge, brown to black dots appears in
the center. Spots merge to form large brown lesions (Figure 1). The experimental set-up at the
field is shown in Figure 2.
Microscopic Characterization
Shown in Figure 3 are the microscopic structures of the causal pathogen of leaf pot on
lettuce. Microscopic observation of Cercospora longissima structure from the infected plants
showed abundant branched mycelium, long and slender multi-celled conidia that are colorless to
dark. Conidiogenous cells and conidia were observed on specimens from infected plants but
were not formed in artificial media.
Figure 1. Leaf spot on leaves
Evaluation Of Plant Extracts Against Cercospora Leaf Spot (Cercospora Longissima)
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Figure 2. Experimental set-up at the field
Figure 3. Conidiogenous cells and conidia of C.longissima
Weekly Assessment Leafspot
Infection
Based on the severity rating which was done prior to the application of plant extracts,
Sunflower has the highest mean of 22.4% and the lowest were from horsetail and control at
20.8% (Table 1). Statistical analysis shows no significant differences of the treatments. The
second rating which was done one week after the first application of plant extracts, generally
showed progress of leaf spot infections in all the treatments. The highest severity rating was
obtained from plants treated with Lantana as 30.60%, followed by Plantago major at 30.53%,
Evaluation Of Plant Extracts Against Cercospora Leaf Spot (Cercospora Longissima)
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Table 1. Means of spot severity rating on lettuce sprayed with plant extracts (%)
TREATMENT
INITIAL
2nd RATING
3rd RATING FINAL
Control
20.80
25.67
30.87
43.13
Angel’s trumpet
21.20
28.40
32.40
46.40
Lantana
21.60
30.60
32.80
45.00
Horsetail
20.80
29.60
35.00
44.80
Neem tree
21.20
27.53
32.87
47.47
Plantago major
22.00
30.53
34.67
48.47
Sunflower
22.40
29.53
34.33
45.60
Horsetail at 29.6%, Sunflower at 29.53%, Angel’s Trumpet at 28.40%, Neem tree at 27.53% and
the least was from the Control at 25.67% (Table 1). The Third leaf spot severity rating taken
after two spraying of the plant extracts is shown in the Table 1. Plants sprayed with plant extracts
generally showed higher severity ratings of leaf spot infection than plants without plant extracts
sprays. Statistical analysis revealed no significant differences between the treatments.
In the final severity rating taken after three sprayings of the plant extracts, all the plant
extract treatments did not show suppression of leaf spot infection as compared to the control
Treatment. The severity ratings of leaf spot infections on plants treated with plant extracts were
higher than the severity rating. The plants without plant extract spray (Table 1). Statistically no
significant differences among the treatments.
The no suppression effect of the plant extracts could either due to low dosage used or
their role is more of insecticidal properties as revealed in previous studies to most of these plants
experimented.
Evaluation Of Plant Extracts Against Cercospora Leaf Spot (Cercospora Longissima)
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Graphical presentation of the progress of leaf spot infections is shown in Figure 4. Initially
infection was somewhat at a high level which ranged from 20%. However, advances in
infections of leaf spots were not as fast, such that the plants were not much affected at the
harvesting or maturity period.
100
90
80
Control
70
Angels'Trumphet
e
c
t
i
on
60
Lantana
I
nf 50
Horsetail
40
Neem Tree
30
L
e
a
f
s
pot
20
Plantago major
% 10
Sunflower
0
7
14
21
28
Number of Days
Figure 4. Weekly assessment of leaf spot infection on lettuce treated with plant extracts
Based on the marketable yield per plot of lettuce which was treated with the different
plant extracts, Neem tree has the highest mean of 36.00 and the lowest were from control and
Angel’s trumpet at 28.00 (Table 2). Statistically analysis shows highly significant differences of
the treatments.
Treatments show that there was an effect on the lettuce that it can be use as
supplementary foliar fertilizer but not as antifungal sprays.
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Table 2. Marketable yield per plot of lettuce treated with plant extracts
TREATMENT
MEAN
Control
28.33
Angel’s Trumpet
28.00
Lantana
31.67
Horsetail
29.00
Neem tree
36.00
Common plantain
31.00
Sunflower
32.00
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SUMMARY, CONCLUSION AND RECOMMENDATION
Summary
The study was conducted at Ambiong, Riverside La Trinidad Benguet from
March to May 2011. It aimed to evaluate the plant extracts against Cercospora leaf spot of
lettuce. Result of the study revealed that the plant extracts used in the study has no effect against
Cercospora leaf spot of lettuce as compared to the control plants.
Conclusion
The plant extracts showed no effect against Cercospora leaf spot of lettuce.
Leaf spot symptoms on the Iceberg lettuce varied from small yellowish spots with brown to
black dots in the center. Adjacent small spots merged to forming large brown lesion. Most of the
plant extracts, except the Angel’s trumpet promoted higher yield than the control.
Recommendation
The plant extracts can be used as supplementary foliar fertilizer but not as
antifungal sprays.
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LITERATURE CITED
AGRIOS, G.M. 1979. Plant Pathology 3rd ed. San Diego, California. Academis Pres. Inc. Pp.
245-300
BRADLEY, P.R. [Ed.]. 1992. British herbal compendium, vol.1. British Herbal Medicine
Association, Bournemouth, U.K.
BERG. 1998. “Phylogenetic relationships among Lactuca (Astenaceae) species and related genera
based on ITS-1 DNA Sequences “. American Journal of Botany 85: 1517-1530. from
http:// www.amibot. Org / cgi / Content /full
BLANCKAERT, J. 2004, “Angel’s Trumpet (Brugmansia arborea) and mydriasis in a child – A
case report”, Bulletin de societe Belge d’Ophtalmologie 292: 53-56. from
http://www. Opthalmologia. be/ download.
FERLA, L. and C. D’EECKENDBRUGGE. 2000. Retrieved - Nov.17, 2007 from America. An
ethnobotanical inventory: Lantana.
FRY, W.F. 1982. Principles of Plant Disease Management. Department of Plant Pathology,
Cornell University, Ithaca New York.
GROENEWALD, M., et al. 2006. Host Range of Cercospora apili and C. beticola and
Description of C. apiicola, a novel species from Celery. Mycologia 98:2 from
http://Koix. Kisti.re.kr/ KISTII
HOMER. 2000. Cercospora Leaf Spot. Retrieved December 03, 2008 from http://www. ppath.
cas. psu. edu/ EXTENSION/ FRUITPATH/ Fruit facts/ Strawberry/ spots.
KNOTT J.F. and R. DEANON. 1967. Vegetable Production in South East Asia. Los Baňos,
Laguna. University of the Philippines, College of Agriculture. Pp. 318-321.
NGITEW, A. 2003. Survey and Identification of fungal diseases of strawberry. BS Thesis.
Benguet State University, La Trinidad, Benguet. Pp. 3, 4, 7, 20 and 31.
PREISSEL, H. G., 2000. Brugmansia and Datura: Angel’s Trumpets and Thorn Apples. Buffalo,
New York. Finely Books. Pp.106-129. Retrieved December 2008 from http://www.
Amazon. Com/ Brugmansia. Datura. Angels Trumpets. Apples /dp/.
SAUER, L. J., 1998. The Once and Future Forest Island Press. P. 49. Retrieved December 09,
2008 from http://books. Google. Com.
SHARMA, V. D. and N. S.PATHANIA 2002. “Let the flower of God bless you”. The Tribune,
Chandigarh, India (Website) from http://www. Tribune dia. com.
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On Lettuce / Oras, Carolyn Daniwes. May 2011
22
SHAW, JULIAN M. H 1999. Nomenclature Notes on Brugmansia. The New Plantsmen. 6 (3):
148-151.
SHOSTECK, ROBT. 1974. Flowers and Plants. An International Lexicon with Biographical
SNOWDON, A. L. 1992. Postharvest Disease and Disorders of Fruits and Vegetables. Vol. 2.
Vegetable CRC Press Inc., Wolfe Pub., Ltd., Florida, USA. Pp. 182-191
WIESS, E.A. 1971. Castor, Sesame and Safflower. Barnes and Noble, New York.
WESTCOTT, C.1960. Plant Disease Handbook. 2nd ed. Van Nostrand Company. Ltd., V.N.C.,
New York. Pp.509-510.
Evaluation Of Plant Extracts Against Cercospora Leaf Spot (Cercospora Longissima)
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23
APPENDICES
Appendix Table 1. Means of spot severity rating on lettuce sprayed with plant extracts (%)
REPLICATION
TOTAL
MEAN
TREATMENT
I
T1
20
21.2
21.2
62.4
20.8
T2
20
22.4
21.2
63.6
21.2
T3
20
21.2
23.6
64.8
21.6
T4
20
22.4
20
62.4
20.8
T5
20
23.6
20
63.6
21.2
T6
20
23.6
22.4
66
22
T7
20
24.8
22.4
67.2
22.4
TOTAL
140
159.2
150.8
450
150
MEAN
21.43
ANALYSIS OF VARIANCE
TABULAR F
SOURCE
DF
SS
MS
F.VALUE
0.5
0.1
Replication
2
26.469
13.234
10.7222
Treatment
6
6.583
1.097
0.8889ns
3.0
4.82
Error
12
14.811 1.234
TOTAL
20
47.863
Coefficient of variation=5.18%
* Significant
** High significant
ns=Not Significant
Evaluation Of Plant Extracts Against Cercospora Leaf Spot (Cercospora Longissima)
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24
Appendix Table 2. Second rating on lettuce sprayed with plant extracts (%)
REPLICATION
TREATMENT
I
II
III
TOTAL
MEAN
T1
24.8
31
21.2
77
25.67
T2
26.8
30
28.4
85.2
28.40
T3
33.2
28.6
30
91.8
30.60
T4
27.8
34.2
26.8
88.8
29.60
T5
26.8
30.2
25.6
82.6
27.53
T6
33.2
29.2
29.2
91.6
30.53
T7
29.2
30.2
29.2
88.6
29.53
TOTAL
201.8
213.4
190.4
605.6
201.87
___________________________________________________________________________
MEAN 28.84
ANALYSIS OF VARIANCE
TABULAR F
SOURCE
DF
SS
MS
F.V
ALUE
0.5
0.1
Replication
2
37.787 18.893
2.7461
Treatment
6
56.983 9.497
1.3804ns
3.0
4.82
Error
12
82.56
6.880
TOTAL
20 177.330
* Significant
Coefficient of variation=9.10%
** Highly significant
ns
=Not Significant
Evaluation Of Plant Extracts Against Cercospora Leaf Spot (Cercospora Longissima)
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25
Appendix Table 3. Third rating on lettuce sprayed with plant extracts (%)
REPLICATION
TREATMENT
I
II
III
TO TAL
M
EAN
T1
27.6
34
31
92.6
30.87
T2
29.2
33
35
97.2
32.40
T3
33.4
33
32
98.4
32.80
T4
35
37
33
105
35.00
T5
29.6
36
33
98.6
32.87
T6
33
36
35
104
34.67
T7
33
35
35
103
34.33
TOTAL
220.8
244
234
698.8
232.93
_____________________________________________________________________________
MEAN 33.28
ANALYSIS OF VARIANCE
TABULAR F
SOURCE
DF
SS
MS
F.V
ALUE
0.5
0.1
Replication
2
38.690
19.345
6.438
Treatment
6
38.971
6.495
2.1616ns
3.0
4.82
Error
12
36.057
3.005
TOTAL
20
113.718
* Significant
Coefficient of variation=5.21%
** Highly significant
ns
=Not Significant
Evaluation Of Plant Extracts Against Cercospora Leaf Spot (Cercospora Longissima)
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26
Appendix Table 4. Final rating on lettuce sprayed with plant extracts (%)
REPLICATION
TREATMENTS
I II III TOTAL MEAN
T1
46
43.6
39.8
129.4
43.13
T2
48
43.8
47.4
139.2
46.40
T3
45.6
45.2
44.2
135
45.00
T4
47.4
43.8
43.2
134.4
44.80
T5
45.4
47.4
49.6
142.4
47.47
T6
47.2
49.6
48.6
145.4
48.47
T7
46.2
46
44.6
136.8
45.60
TOTAL
325.8
319.4
317.4
962.6
320.87
____________________________________________________________________________
MEAN 45.84
ANALYSIS OF VARIANCE
TABULAR F
SOURCE
DF
SS
MS
F.V
ALUE
0.5
0.1
Replication
2
5.501
2.75
0.6739
Treatment
6
57.090
9.515
2.3312ns
3.0
4.82
Error
12 48.979
4.082
TOTAL
20 111.570
* Significant
Coefficient of variation=4.41%
** Highly significant
ns
=Not Significant
Evaluation Of Plant Extracts Against Cercospora Leaf Spot (Cercospora Longissima)
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27
Appendix table 5. Marketable yield per plot of lettuce treated with plant extracts
REPLICATION
TREATMENT
TOTAL
MEAN
I
II
III
T1
75
95
85
255
85
T2
73
95
85
253
84.33
T3
90
90
105
285
95
T4
75
90
95
260
86.67
T5
100
115
110
325
108.33
T6
85
90
105
280
93.33
T7
85
100
105
290
96.67
TOTAL
583
675
690
1948
649.33
MEAN
92.77
ANALYSIS OF VARIANCE
TABULAR F
SOURCE
DF
SS MS
F. VALUE
0.5 0.1
Block 2 958.9523 479.47 14.37** 3.89 6.93
Treatment 6 1294.476 215.746 6.47** 3.0 6.93
Error 12 400.3809 33.365
TOTAL 20 2653.810
*Significant
**Highly Significant
ns =Not Significant
Evaluation Of Plant Extracts Against Cercospora Leaf Spot (Cercospora Longissima)
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ORAS, CAROLYN DANIWES. MAY 2011. Evaluation of Plant Extracts against
Cercospora Leaf Spot (Cercospora longissima) on Lettuce. Ambiong Riverside, La Trinidad
Benguet.
Adviser: Andres A. Basalong, MSc.
ABSTRACT
The study was conducted at the Ambiong, Riverside La Trinidad Benguet from March to
May 2011. The study aimed to determine the efficacy of botanical fungicides against Cercospora
leaf spot of Iceberg lettuce.
Leaf spot symptoms on the Iceberg lettuce cultivar appeared as small yellowish spots
with brown to black dots in the center. Larger spot form from the merging of adjacent small
spots.
Results of the study showed that the plant extracts used in this experiment did not
suppress Cercospora leaf spot infection on lettuce. The plants treated with plant extracts as
botanical fungicides had infection of Cercospora leaf spot higher than the infection of untreated
plants.
1
INTRODUCTION
Lettuce (Lactuca sativa) is a native to the Mediterranean Region, where it has been
cultivated for several millennia. It probably spread into the rest of Europe during the Roman
occupation. When it was introduced into the America’s in the 15th Century, lettuce become
popular in the new world and now the major salad crop and become important in most countries.
Lettuce is unique among the major vegetables in that it is used almost exclusively as a fresh raw
product. This can be grown as a field crop or else under the protection of glass or plastic
(Snowdon, 1992).
Lettuce is a temperate annual or biennial plant of the daisy family Asteraceae or
Compositae. It is most often grown as a leaf vegetable. In many countries, it is typically eaten
cold, raw, in salads, sandwiches, hamburgers, tacos and in many other dishes. In some places,
including china, lettuce is typically eaten cooked and use of the stem is as important as use of the
leaf. It has a short stem initially, but when it gradually blooms, the stem and branches lengthens
and produces many flower heads that look like those of dandelions, but smaller. This is referred
to as bolting. When grown for food, lettuce is harvested before it bolts (Berg, 1998).
Lettuce is usually grown commonly in semi-temperate regions like Benguet. It can be
planted anytime of the year, provided that there is abundant supply of water. It is best however to
plant from September to February when climate is relatively cool (Knott and Deanon, 1967).
Lettuce growers in Benguet often observe and complain about destructive diseases of
lettuce. These diseases inflict leaf spots that lead to economic losses due to low quality of the
harvest or no harvest if severely infected.
As cited by Snowdon (1992) lettuce is a fast income generating agricultural produce,
however, pests and disease and improper postharvest handing contributes to the great losses of
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income to producers. It is a highly perishable crop that can be damaged easily due to disease
infections and adverse environmental conditions. Being a high value commercial crop, losses
through pathogen infections should be minimized. Moreover, Fry (1982) mentioned that more
than 40% of the produced is considered as loss due to over trimming, color changes and nutrition
depletion. Climate is known to be capable of causing large reduction in yield by directly
affecting the plants as well as favorably enhancing pathogens, insect and weed attacks.
Leaf spot of lettuce is one of the major diseases that often limit or reduce the production
of lettuce. Due to leaf spot infection, cleaning of outer wrapper leaves may be intense resulting to
reduction of weight, size and exposure of pale green inner leaves. Further, marketability would
also be reduced. Using non-chemical alternative control strategies against leaf spot of lettuce is
in direly important for the reason that lettuce is a salad crop. Since, potent fungicides used
against lettuce leaf spot and other pesticides for other pests would not be neutralize, because
lettuce as salad crop is not subjected to cooking.
Discovery of non-chemical products against leaf spot that is indigenous in the locality or
those that are available from other source but could that be adopted and propagated within the
locality could serve as a ready source of botanical fungicides against leaf spot. The positive
result of the study would conform to the trend of current farming that is organic agriculture.
The study was conducted to evaluate the efficacy of selected plant extracts against
Cercospora longissima.
The experiment was conducted at Ambiong, Riverside La Trinidad Benguet from March
to May 2011.
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3
REVIEW OF LITERATURE
Nature of Cercospora Leaf Spot
Cercospora spot (Cercospora longissima). Cercospora spot of lettuce is found
predominantly in tropical countries. The spots appear as minute water soaked brown spots, each
surrounded by a pale halo and appearing initially on the outer leaves of lettuce. The lesions may
enlarge into irregular brown areas bounded by the leaf veins and coalesce to form large blotches.
In a humid atmosphere there is a grayish to buff growth of mould giving rise to spores (conidia).
This disease may also spread to younger leaves (Snowdon, 1992). Likewise Groenewald (2006)
describe Cercospora leaf spot to initially present itself as tiny circular or oval spots on plant
leaves that enlarge with time. The spots can vary in color from dark green to brown with or
without maroon or purple margins. In later stages of the disease on the leaves or flowers may
become yellow and fall off the stems, and leaves on edible crops may become brownish-gray
color as they dry out and die completely.
Development of Cercospora leaf spot disease begins when the fungus spores are
dispersed by rain irrigation water and wind. Germination occurs in humid conditions, usually
during late spring and summer, and fungus growth is encouraged by frequently damp leaves.
Plants that measure in the fall may escape acute infection. In general, the more rain, the worse
the disease spreads. Cercospora infests seeds and crop residue where it harbors over the winter
(Groenewald, 2006).
Homer (2000) also cited that Cercospora leaf spot symptoms development is most
common on leaves but may occur on most above ground plant parts. Lesions are initially visible
on the upper leaf surface as small purple spots. The spots enlarged slightly with age up to ¼ inch
and may coalesce. The tissue in the center of the spot changes from purple to tan or gray and
Evaluation Of Plant Extracts Against Cercospora Leaf Spot (Cercospora Longissima)
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4
eventually become white. The margin of the spots remains purple or brown giving the lesion a
“bird’s eye “appearance. Infection sites appear as indistinct tan or bluish areas on lower leaf
surface. Symptoms expression is variable depending on the age of the leaf, susceptibility of the
cultivar or species, fungal strain and environmental conditions.
Leaf spot may reach economic threshold levels, provided young leaves and inoculum are
present, under conditions of high temperature and long period of leaf wetness. Research result
show most severe infection of young leaves to occur during periods of leaf wetness from 12 to
96 hours when temperatures fall in the range of 59-68oF or 15-20oC. This data suggest that
fungicide treatment should be applied early spring and after renovation of inoculum is present
(Ngitew, 2003).
Several species of Cercospora are responsible for the diseases on the various hosts; some
Cercospora species have Mycosphaerella as their teleomorph. The fungus produces long,
slender, color less, to dark, straight to slightly curved, multicellular conidia on short dark
conidiophores. Conidiophores arise from the plant surface in clusters through the stomata and
form conidia successively on new growing tips. Conidia are detached easily and are often blown
long distances by the wind. The fungus is favored by high temperatures and therefore is most
destructive in the summer months and in warmer climates. Most Cercospora species produce the
nonspecific toxin cercosporin, which acts as a photosensitizing agent in the plant cells; it kills
cells only in the light. The toxin incites the production of reactive atomic oxygen in the cells.
Although Cercospora spores need water to germinate and penetrate, heavy dews seem to be
sufficient for infection. The pathogen over seasons in or on the seed and as minute black stomata
in old infected leaves (Agrios, 1979).
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There are several types of lettuce, differing in leaf shape and form and in the tendency to form a
‘heart’ or ‘head’ (Berg, 1998).
Control
Cercospora disease is controlled by using disease-free seed or seed least three years old,
by which time the fungus in the seed has died; by using crop rotations with hosts not affected by
the same Cercospora species; and by spraying the plants, both in the seed bed and in the field,
with appropriate fungicides (Fry, 1982).
Other Diseases that is very common in Lettuce (Westcott, 1960)
Alternaria spot. This is caused by various species of Alternaria, has been recorded on
lettuce in several countries, on Chicory in India and on endive in Greece, on Italy and Argentina.
Endive cultivars are generally much more susceptible than Chicory to infection by Alternaria
cichorii.
Myconcentrospora spot. This has been recorded on outdoor lettuce in France and in the
UK following heavy rains and the disease also occurs in the USA. The causal fungus is
Mycocentrospore acerina. Leaf spot are circular to angular with pale brown centers and darken
margins, sometimes surrounded by a board band of grayish-green. Irregularly shaped lesions
develop on the midribs of exposed leaves. Control by fungicides sprays has been suggested.
Myrothecium rot. This is caused by Myrothecium roridum, and it has been recorded
outdoor lettuce in sprain. Warm moist weather is conductive to infection, resulting in the
formation of circular spots on both sides of the leaf blades.
Phytopthora rot. It has been recorded in Australia on lettuce as a firm dark stem rot
extending upwards into the head. The disease was found only during winter in badly drained
Evaluation Of Plant Extracts Against Cercospora Leaf Spot (Cercospora Longissima)
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6
fields. The causal fungus was a strain of Phytophthora porri which had an optimal growth
temperature of 15o C and failed to infect leeks on cabbages.
Phythium rot. This is caused by Phythium aphanidermatum, affects lettuce in India,
leaves in with the ground are invaded, become water soaked and decay rapidly. In the
Netherlands, species of Phythium are recorded as components of bottom rot.
Sclerotium rot. This is caused by Sclerotium rolfsii occasionally recorded on lettuce and
endive in the Southern USA. The fungus is favored by warm wet conditions and attacks leaves in
contact with the soil, giving rise to silky white mould and spherical resting bodies (sclerotia).
Plants with Antifungal Properties
Angel’s Trumpet(Brugmansia suarveolens). Angel’s Trumpet is a genus of seven species
of flowering plants in the family Solanaceae. They are known as Angel’s Trumpets sharing that
name with the closely related genus Datura. Brugmansia are long-lived, woody trees or bushes,
with pendulous not erect flowers, that have no spines on their fruit. Datura species are
herbaceous bushes with erect (not pendulous) flowers, and most have spines on their fruit
(Preissel, 2000). Brugmansia are large shrubs or small trees, reaching heights of 3-11 m, with tan
slightly rough bark. The leaves are alternate, generally large 10-30 cm long and 4-18 cm broad,
with an entire or coarsely toothed margin, and are covered with fine hairs. The name Angel’s
Trumpet refers to the large, very dramatic, pendulous trumpet-shaped flowers, 14-50 cm to 50-8
cm long and 10-35 cm across at the wide end. They are white, yellow, pink, orange or red, and
have a delicate, attractive scent with light, lemony over-tones, most noticeable in early evening.
Flowers may be single or double (Shaw, 1999). As with Datura all parts of Brugmansia are
highly toxic. The plants are sometimes ingested for recreational or Shananic intoxication as the
plant contains the tropane alkaloids scopolamine and atropine; however because the potency of
Evaluation Of Plant Extracts Against Cercospora Leaf Spot (Cercospora Longissima)
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7
the toxic compounds in the plant is variable the degree of intoxication is unpredictable and can
be fatal (Blanckaert, 2004).
Horsetail(Ricinus communis). Is a species of flowering plant in the spurge family,
Euphorbiaceae. It belongs to a monotypic genus, Ricinus, and subtribe, Riciniae. The evolution
of castor and its relation to other species is currently being studied. Its seed is the castor bean
which, despite its name is not a true bean. Castor is indigenous to the Southeastern
Mediterranean Basin, Eastern Africa, and India but is widespread throughout tropical regions.
Castor seed is the source of castor oil, 40% and 60% oil that is also present in lower
concentrations throughout the plant. The seeds from the castor bean plant, Ricinus communis, are
poisonous to people, animals and insects. One of the main toxic proteins is “ricin”, named by
Still Mark in 1888 when he tested the beans extract on red blood cells and saw them agglutinate.
Now we know that the agglutination was due to another toxin that was also present, called RCA
(Ricinus communis agglutinin). Poisoning by ingestion of the castor bean is due to ricin, not
RCA, because RCA does not penetrate the intestinal wall, and does not affect red blood cells
unless given intravenously. If RCA is injected into the blood, it will cause the red blood cells to
agglutinate and burst is hemolysis (Wiess, 1971).
Lantana (Lantana camara L). It consists of more than 150 species of shrubs and
herbaceous perennials, of the vervain family Verbenaceae. Lantanas are mostly natives of the
tropics and subtropics of America but some are natives of warm parts of the Old World. Their
name is an ancient one used for the quite unrelated genus Viburnum. Wild lantanas are hairy and
often prickly-stemmed. If rubbed and bruised, their leaves usually have a pungent odor. Verbena-
like flowers are formed in clusters from the leaf axils or at the ends of branches. The small berry-
like fruits contain seeds. In some regions, lantanas grow wild as weeds, chiefly spread by birds
Evaluation Of Plant Extracts Against Cercospora Leaf Spot (Cercospora Longissima)
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8
that are very fond of their juicy fruits. Lantana leaves can be used as a soothing agent in cases of
insect stings, skin eruptions, cuts scrapes, ulcerations, the itch of measles and chicken pox,
parasites such as scabies. However, there often conflicting reports on its use as an herbal
medicine. The green berries are toxic and there has been one human fatality attributed to them.
Animals will also be affected by eating these plants (Ferla and D’ Eeckendbrugge ,2000).
Neem tree (Azadirachta indica). As versatile as “kakawe” is the neem. In 1962, an Indian
scientist found out thaqt neem seed extract proved operative as an insect repellant. Discovery of
azadiracthan, a principal anti- feedant, was reported in 1986. Independent experiments by other
respected scientists from all over the world disclosed other neem compounds, among them
vitasinin and salanorin.
Sap from the neem tree has been tried as an insecticide and was found to destroy vicadas
and astracods infesting rice fields. Neem cake- the residue left after oil is extracted from neem
seeds- when incorporated in the soil kills nematodes.
Several experiments conducted at the International Rice Research Institute showed that
leafhoppers feed less, grow poorly and lay fewer eggs on rice plants that have been sprayed with
neem oil.
For its part, the Bureau of plant Industry of the Department of Agriculture once
experimented the effects of neem oil extract on the corn borer, the prime suspect behind the 20-
80 percent losses in domestic corn yields. The study confirms neem oil can destroy 93.3 percent
of the dreaded pest. Neem is unique among plants with pesticidal properties since it has so many
different effects on pests: It acts as a broad-spectrum repellent, insect growth regulator (it causes
deformities in the insect’s offspring) and insect poison. It discourages feeding by making plants
unpalatable to insects or suppresses the insect’s appetite (anti-feedant effect); if they still attack,
Evaluation Of Plant Extracts Against Cercospora Leaf Spot (Cercospora Longissima)
On Lettuce / Oras, Carolyn Daniwes. May 2011
9
it inhibits their ability to moult and lay eggs. Unlike most botanical insecticides, neem also has a
somewhat “systemic” effect. This means that plants can take up neem extracts through their roots
and leaves, spreading the material throughout the plant tissues (Bradley, 1992).
Sunflower (Helianthus annus L.). Are annual plants native to the Americas, those posses
a large inflorescence (flowering head). The florets inside the circular head are yellow, maroon,
orange, or other colors. The florets within circular head are called disc florets, which mature into
seeds. The florets within the sunflower’s cluster are arranged in a spiral pattern. This pattern
produces the most efficient packing of seeds within the flower head. To grow well, sunflowers
need full sun. They grow best fertile, moist; well-drained soil with a lot of mulch. The most
serious diseases of sunflower are caused by fungi. The major diseases include rust, downey
mildew,verticillum wilt, sclerotinia stalk and head rot, phoma black stem and leaf spot. The
severity of these disease effects on total crop yield might be ranked: 1) sclerotinia, 2)
verticillium, 3) rust (recently more severe), 4) phoma, and 5) downly mildew. Resistance to rust,
downy mildew, and verticillium wilt has been incorporated into improved sunflower germplasm.
The growth of sunflower as an oilseed crop has rivaled that of soybean, with both increasing
production over 6-fold since the 1930’s. Sunflower oil is generally considered a premium oil
because of its light color, high level of unsaturated fatty acids and lack of linolenic acid, bland
flavor and high smoke points (Shosteck, 1974).
Common plantain (Plantago major). Is a species of Plantago, family Plantaginaceae. It is
widely naturalized elsewhere in the world, where it is a common Plantain in some areas where it
is introduced, particularly North America. Another one of its common names was “Soldiers
Herb” for its use on the battlefield as a dressing. It is an herbaceous perennial plant with a rosette
of leaves 15-30 cm diameter. Each leaf is oval, 5-20 cm long and 4-9 cm broad, rarely up to 30
Evaluation Of Plant Extracts Against Cercospora Leaf Spot (Cercospora Longissima)
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10
cm long and 17 cm broad, with an acute apex and a smooth margin; there are five to nine
conspicuous veins. The flowers are small, greenish-brown with purple stamens, produced in a
dense spike 5-15 cm long on top of a stem 13-15 cm tall (Sauer, 1998).
Evaluation Of Plant Extracts Against Cercospora Leaf Spot (Cercospora Longissima)
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11
MATERIALS AND METHOD
Collection and Diagnosis of Diseased Specimens
Infected leaves of lettuce were collected from the experimental farm in Ambiong,
Riverside La Trinidad Benguet. The specimens gathered were sealed in paper bags and brought
to the laboratory for diagnosis to confirm the causal pathogen.
Symptomatology and Microscopic Activity
Symptomatology and microscopic observations were done and recorded. The
Microscopic examination of the structures of the pathogen from leaf samples was done to
observe the shape, size, and color of the spores and filaments.
Isolation of Pathogen
The collected diseased plants were washed with tap water to remove dirt. Five pieces at
2-3 mm2 were cut within progressively diseased portion on the leaves. The pieces of tissues were
disinfected in 10% chlorox for one minute, washed in three changes of sterile water and blot
dried on a sterile tissue paper. Five pieces of cut tissues from the leaves were planted in plated
PDA to isolate the pathogen. Colonies of the pathogen were re-isolated in test tube slants to
obtain pure culture. The pure cultures were sampled for microscopic observation to confirm the
causal pathogen of lettuce leaf spot.
Evaluation Of Plant Extracts Against Cercospora Leaf Spot (Cercospora Longissima)
On Lettuce / Oras, Carolyn Daniwes. May 2011
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Collection and Preparation
of Botanical Fungicides
Plants evaluated for fungicidal properties were collected within Benguet, wherever it
could be found. These were processed by macerating to obtain sap extracts. Botanical plants used
were selected based on their use as medicinal plants or reported to be effective against pathogens
and insect pest. The preparation of the botanicals followed the procedure using ethanol for
extraction. For solvent extract, 30 grams of botanical plants were washed with tap water,
chopped and placed in an Erlenmeyer flask. Ethyl alcohol (95 percent) was used to soak the
plants. Tissues were macerated using the mortar and pestle. The suspensions were left to stand
for 2-3 days. The tissues were separated from the liquid portion using a filter paper. For every
0.50mg of the plants extract, 1 ml of acetone was mixed to dissolve the plant extracts.
In the water extract procedure, 20 grams of botanical plants were disinfected with chlorox
then rinsed with distilled water. Following the weight/ volume formula, 20 grams of botanical
plants were soaked in 20 ml of water.
Seedbed Preparation and
Seedling Management
A seedbed was prepared for the growing of lettuce seedlings, Iceberg variety. Three (3)
weeks after sowing, the seedlings of lettuce were transplanted in the experimental area.
All cultural practices involved in caring lettuce seedlings such as watering, replanting
damaged by cutworms, and control of insect pest were done in all the treatments. Seedlings were
not protected with fungicides from germination to transplanting up to the termination of the
experiment.
Evaluation Of Plant Extracts Against Cercospora Leaf Spot (Cercospora Longissima)
On Lettuce / Oras, Carolyn Daniwes. May 2011
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Field Trial and Planting
The lettuce seedlings that were free from Cercospora leaf spot were transplanted in the
experimental field. The plots measured 0.80m x 5m each. Double row planting was done per
plot. Cultural practices were done regularly such as watering, weeding and hilling up. No
chemicals and inorganic fertilizer where added except for the spraying of the different plant
extracts. Treatments were replicated three times following the Randomized Complete Block
Design (RCBD).
The Treatments were:
T1- Control
T2- Angel’s Trumpet (Brugmansia suarveolens)
T3- Lantana (Lantana camara)
T4- Horsetail (Ricinus communis)
T5- Neem (Azadirachta indica)
T6- Common plantain (Plantago major)
T7- Sunflower (Helianthus annus L.)
Data Gathered were:
1. Diagnostic activity
a. Symptom description
b. Morphological Characteristics of the pathogen from the fresh plant samples and
culture media.
c. Cultural characteristics, colony (color, spread or growth and unit time)
Evaluation Of Plant Extracts Against Cercospora Leaf Spot (Cercospora Longissima)
On Lettuce / Oras, Carolyn Daniwes. May 2011
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2. Field
a. Infection rating. The scale developed by the British Mycological Society
(Anon, 1947) was used in the study.
Rating Scale Description
1 0 No infection
2
10% Only few leaves affected, up to one spot
3 15% Nearly every plant affected
4 25% Every plant affected and about half of the leaf area destroyed
by spot
5 50% About three quarters of the leaf is destroyed by spots
Evaluation Of Plant Extracts Against Cercospora Leaf Spot (Cercospora Longissima)
On Lettuce / Oras, Carolyn Daniwes. May 2011
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RESULTS AND DISCUSSION
Disease Symptoms
Cercospora longissima infection also called frog eyespot first appears as small yellowish
spots on the upper leaf surface. As the spots develop and enlarge, brown to black dots appears in
the center. Spots merge to form large brown lesions (Figure 1). The experimental set-up at the
field is shown in Figure 2.
Microscopic Characterization
Shown in Figure 3 are the microscopic structures of the causal pathogen of leaf pot on
lettuce. Microscopic observation of Cercospora longissima structure from the infected plants
showed abundant branched mycelium, long and slender multi-celled conidia that are colorless to
dark. Conidiogenous cells and conidia were observed on specimens from infected plants but
were not formed in artificial media.
Figure 1. Leaf spot on leaves
Evaluation Of Plant Extracts Against Cercospora Leaf Spot (Cercospora Longissima)
On Lettuce / Oras, Carolyn Daniwes. May 2011
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Figure 2. Experimental set-up at the field
Figure 3. Conidiogenous cells and conidia of C.longissima
Weekly Assessment Leafspot
Infection
Based on the severity rating which was done prior to the application of plant extracts,
Sunflower has the highest mean of 22.4% and the lowest were from horsetail and control at
20.8% (Table 1). Statistical analysis shows no significant differences of the treatments. The
second rating which was done one week after the first application of plant extracts, generally
showed progress of leaf spot infections in all the treatments. The highest severity rating was
obtained from plants treated with Lantana as 30.60%, followed by Plantago major at 30.53%,
Evaluation Of Plant Extracts Against Cercospora Leaf Spot (Cercospora Longissima)
On Lettuce / Oras, Carolyn Daniwes. May 2011
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Table 1. Means of spot severity rating on lettuce sprayed with plant extracts (%)
TREATMENT
INITIAL
2nd RATING
3rd RATING FINAL
Control
20.80
25.67
30.87
43.13
Angel’s trumpet
21.20
28.40
32.40
46.40
Lantana
21.60
30.60
32.80
45.00
Horsetail
20.80
29.60
35.00
44.80
Neem tree
21.20
27.53
32.87
47.47
Plantago major
22.00
30.53
34.67
48.47
Sunflower
22.40
29.53
34.33
45.60
Horsetail at 29.6%, Sunflower at 29.53%, Angel’s Trumpet at 28.40%, Neem tree at 27.53% and
the least was from the Control at 25.67% (Table 1). The Third leaf spot severity rating taken
after two spraying of the plant extracts is shown in the Table 1. Plants sprayed with plant extracts
generally showed higher severity ratings of leaf spot infection than plants without plant extracts
sprays. Statistical analysis revealed no significant differences between the treatments.
In the final severity rating taken after three sprayings of the plant extracts, all the plant
extract treatments did not show suppression of leaf spot infection as compared to the control
Treatment. The severity ratings of leaf spot infections on plants treated with plant extracts were
higher than the severity rating. The plants without plant extract spray (Table 1). Statistically no
significant differences among the treatments.
The no suppression effect of the plant extracts could either due to low dosage used or
their role is more of insecticidal properties as revealed in previous studies to most of these plants
experimented.
Evaluation Of Plant Extracts Against Cercospora Leaf Spot (Cercospora Longissima)
On Lettuce / Oras, Carolyn Daniwes. May 2011
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Graphical presentation of the progress of leaf spot infections is shown in Figure 4. Initially
infection was somewhat at a high level which ranged from 20%. However, advances in
infections of leaf spots were not as fast, such that the plants were not much affected at the
harvesting or maturity period.
100
90
80
Control
70
Angels'Trumphet
e
c
t
i
on
60
Lantana
I
nf 50
Horsetail
40
Neem Tree
30
L
e
a
f
s
pot
20
Plantago major
% 10
Sunflower
0
7
14
21
28
Number of Days
Figure 4. Weekly assessment of leaf spot infection on lettuce treated with plant extracts
Based on the marketable yield per plot of lettuce which was treated with the different
plant extracts, Neem tree has the highest mean of 36.00 and the lowest were from control and
Angel’s trumpet at 28.00 (Table 2). Statistically analysis shows highly significant differences of
the treatments.
Treatments show that there was an effect on the lettuce that it can be use as
supplementary foliar fertilizer but not as antifungal sprays.
Evaluation Of Plant Extracts Against Cercospora Leaf Spot (Cercospora Longissima)
On Lettuce / Oras, Carolyn Daniwes. May 2011
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Table 2. Marketable yield per plot of lettuce treated with plant extracts
TREATMENT
MEAN
Control
28.33
Angel’s Trumpet
28.00
Lantana
31.67
Horsetail
29.00
Neem tree
36.00
Common plantain
31.00
Sunflower
32.00
Evaluation Of Plant Extracts Against Cercospora Leaf Spot (Cercospora Longissima)
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SUMMARY, CONCLUSION AND RECOMMENDATION
Summary
The study was conducted at Ambiong, Riverside La Trinidad Benguet from
March to May 2011. It aimed to evaluate the plant extracts against Cercospora leaf spot of
lettuce. Result of the study revealed that the plant extracts used in the study has no effect against
Cercospora leaf spot of lettuce as compared to the control plants.
Conclusion
The plant extracts showed no effect against Cercospora leaf spot of lettuce.
Leaf spot symptoms on the Iceberg lettuce varied from small yellowish spots with brown to
black dots in the center. Adjacent small spots merged to forming large brown lesion. Most of the
plant extracts, except the Angel’s trumpet promoted higher yield than the control.
Recommendation
The plant extracts can be used as supplementary foliar fertilizer but not as
antifungal sprays.
Evaluation Of Plant Extracts Against Cercospora Leaf Spot (Cercospora Longissima)
On Lettuce / Oras, Carolyn Daniwes. May 2011
21
LITERATURE CITED
AGRIOS, G.M. 1979. Plant Pathology 3rd ed. San Diego, California. Academis Pres. Inc. Pp.
245-300
BRADLEY, P.R. [Ed.]. 1992. British herbal compendium, vol.1. British Herbal Medicine
Association, Bournemouth, U.K.
BERG. 1998. “Phylogenetic relationships among Lactuca (Astenaceae) species and related genera
based on ITS-1 DNA Sequences “. American Journal of Botany 85: 1517-1530. from
http:// www.amibot. Org / cgi / Content /full
BLANCKAERT, J. 2004, “Angel’s Trumpet (Brugmansia arborea) and mydriasis in a child – A
case report”, Bulletin de societe Belge d’Ophtalmologie 292: 53-56. from
http://www. Opthalmologia. be/ download.
FERLA, L. and C. D’EECKENDBRUGGE. 2000. Retrieved - Nov.17, 2007 from America. An
ethnobotanical inventory: Lantana.
FRY, W.F. 1982. Principles of Plant Disease Management. Department of Plant Pathology,
Cornell University, Ithaca New York.
GROENEWALD, M., et al. 2006. Host Range of Cercospora apili and C. beticola and
Description of C. apiicola, a novel species from Celery. Mycologia 98:2 from
http://Koix. Kisti.re.kr/ KISTII
HOMER. 2000. Cercospora Leaf Spot. Retrieved December 03, 2008 from http://www. ppath.
cas. psu. edu/ EXTENSION/ FRUITPATH/ Fruit facts/ Strawberry/ spots.
KNOTT J.F. and R. DEANON. 1967. Vegetable Production in South East Asia. Los Baňos,
Laguna. University of the Philippines, College of Agriculture. Pp. 318-321.
NGITEW, A. 2003. Survey and Identification of fungal diseases of strawberry. BS Thesis.
Benguet State University, La Trinidad, Benguet. Pp. 3, 4, 7, 20 and 31.
PREISSEL, H. G., 2000. Brugmansia and Datura: Angel’s Trumpets and Thorn Apples. Buffalo,
New York. Finely Books. Pp.106-129. Retrieved December 2008 from http://www.
Amazon. Com/ Brugmansia. Datura. Angels Trumpets. Apples /dp/.
SAUER, L. J., 1998. The Once and Future Forest Island Press. P. 49. Retrieved December 09,
2008 from http://books. Google. Com.
SHARMA, V. D. and N. S.PATHANIA 2002. “Let the flower of God bless you”. The Tribune,
Chandigarh, India (Website) from http://www. Tribune dia. com.
Evaluation Of Plant Extracts Against Cercospora Leaf Spot (Cercospora Longissima)
On Lettuce / Oras, Carolyn Daniwes. May 2011
22
SHAW, JULIAN M. H 1999. Nomenclature Notes on Brugmansia. The New Plantsmen. 6 (3):
148-151.
SHOSTECK, ROBT. 1974. Flowers and Plants. An International Lexicon with Biographical
SNOWDON, A. L. 1992. Postharvest Disease and Disorders of Fruits and Vegetables. Vol. 2.
Vegetable CRC Press Inc., Wolfe Pub., Ltd., Florida, USA. Pp. 182-191
WIESS, E.A. 1971. Castor, Sesame and Safflower. Barnes and Noble, New York.
WESTCOTT, C.1960. Plant Disease Handbook. 2nd ed. Van Nostrand Company. Ltd., V.N.C.,
New York. Pp.509-510.
Evaluation Of Plant Extracts Against Cercospora Leaf Spot (Cercospora Longissima)
On Lettuce / Oras, Carolyn Daniwes. May 2011
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APPENDICES
Appendix Table 1. Means of spot severity rating on lettuce sprayed with plant extracts (%)
REPLICATION
TOTAL
MEAN
TREATMENT
I
T1
20
21.2
21.2
62.4
20.8
T2
20
22.4
21.2
63.6
21.2
T3
20
21.2
23.6
64.8
21.6
T4
20
22.4
20
62.4
20.8
T5
20
23.6
20
63.6
21.2
T6
20
23.6
22.4
66
22
T7
20
24.8
22.4
67.2
22.4
TOTAL
140
159.2
150.8
450
150
MEAN
21.43
ANALYSIS OF VARIANCE
TABULAR F
SOURCE
DF
SS
MS
F.VALUE
0.5
0.1
Replication
2
26.469
13.234
10.7222
Treatment
6
6.583
1.097
0.8889ns
3.0
4.82
Error
12
14.811 1.234
TOTAL
20
47.863
Coefficient of variation=5.18%
* Significant
** High significant
ns=Not Significant
Evaluation Of Plant Extracts Against Cercospora Leaf Spot (Cercospora Longissima)
On Lettuce / Oras, Carolyn Daniwes. May 2011
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Appendix Table 2. Second rating on lettuce sprayed with plant extracts (%)
REPLICATION
TREATMENT
I
II
III
TOTAL
MEAN
T1
24.8
31
21.2
77
25.67
T2
26.8
30
28.4
85.2
28.40
T3
33.2
28.6
30
91.8
30.60
T4
27.8
34.2
26.8
88.8
29.60
T5
26.8
30.2
25.6
82.6
27.53
T6
33.2
29.2
29.2
91.6
30.53
T7
29.2
30.2
29.2
88.6
29.53
TOTAL
201.8
213.4
190.4
605.6
201.87
___________________________________________________________________________
MEAN 28.84
ANALYSIS OF VARIANCE
TABULAR F
SOURCE
DF
SS
MS
F.V
ALUE
0.5
0.1
Replication
2
37.787 18.893
2.7461
Treatment
6
56.983 9.497
1.3804ns
3.0
4.82
Error
12
82.56
6.880
TOTAL
20 177.330
* Significant
Coefficient of variation=9.10%
** Highly significant
ns
=Not Significant
Evaluation Of Plant Extracts Against Cercospora Leaf Spot (Cercospora Longissima)
On Lettuce / Oras, Carolyn Daniwes. May 2011
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Appendix Table 3. Third rating on lettuce sprayed with plant extracts (%)
REPLICATION
TREATMENT
I
II
III
TO TAL
M
EAN
T1
27.6
34
31
92.6
30.87
T2
29.2
33
35
97.2
32.40
T3
33.4
33
32
98.4
32.80
T4
35
37
33
105
35.00
T5
29.6
36
33
98.6
32.87
T6
33
36
35
104
34.67
T7
33
35
35
103
34.33
TOTAL
220.8
244
234
698.8
232.93
_____________________________________________________________________________
MEAN 33.28
ANALYSIS OF VARIANCE
TABULAR F
SOURCE
DF
SS
MS
F.V
ALUE
0.5
0.1
Replication
2
38.690
19.345
6.438
Treatment
6
38.971
6.495
2.1616ns
3.0
4.82
Error
12
36.057
3.005
TOTAL
20
113.718
* Significant
Coefficient of variation=5.21%
** Highly significant
ns
=Not Significant
Evaluation Of Plant Extracts Against Cercospora Leaf Spot (Cercospora Longissima)
On Lettuce / Oras, Carolyn Daniwes. May 2011
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Appendix Table 4. Final rating on lettuce sprayed with plant extracts (%)
REPLICATION
TREATMENTS
I II III TOTAL MEAN
T1
46
43.6
39.8
129.4
43.13
T2
48
43.8
47.4
139.2
46.40
T3
45.6
45.2
44.2
135
45.00
T4
47.4
43.8
43.2
134.4
44.80
T5
45.4
47.4
49.6
142.4
47.47
T6
47.2
49.6
48.6
145.4
48.47
T7
46.2
46
44.6
136.8
45.60
TOTAL
325.8
319.4
317.4
962.6
320.87
____________________________________________________________________________
MEAN 45.84
ANALYSIS OF VARIANCE
TABULAR F
SOURCE
DF
SS
MS
F.V
ALUE
0.5
0.1
Replication
2
5.501
2.75
0.6739
Treatment
6
57.090
9.515
2.3312ns
3.0
4.82
Error
12 48.979
4.082
TOTAL
20 111.570
* Significant
Coefficient of variation=4.41%
** Highly significant
ns
=Not Significant
Evaluation Of Plant Extracts Against Cercospora Leaf Spot (Cercospora Longissima)
On Lettuce / Oras, Carolyn Daniwes. May 2011
27
Appendix table 5. Marketable yield per plot of lettuce treated with plant extracts
REPLICATION
TREATMENT
TOTAL
MEAN
I
II
III
T1
75
95
85
255
85
T2
73
95
85
253
84.33
T3
90
90
105
285
95
T4
75
90
95
260
86.67
T5
100
115
110
325
108.33
T6
85
90
105
280
93.33
T7
85
100
105
290
96.67
TOTAL
583
675
690
1948
649.33
MEAN
92.77
ANALYSIS OF VARIANCE
TABULAR F
SOURCE
DF
SS MS
F. VALUE
0.5 0.1
Block 2 958.9523 479.47 14.37** 3.89 6.93
Treatment 6 1294.476 215.746 6.47** 3.0 6.93
Error 12 400.3809 33.365
TOTAL 20 2653.810
*Significant
**Highly Significant
ns =Not Significant
Evaluation Of Plant Extracts Against Cercospora Leaf Spot (Cercospora Longissima)
On Lettuce / Oras, Carolyn Daniwes. May 2011
Document Outline
- Evaluation of Plant Extracts againstCercospora Leaf Spot (Cercospora longissima) on Lettuce
- BIBLIOGRAPHY
- ABSTRACT
- INTRODUCTION
- REVIEW OF LITERATURE
- MATERIALS AND METHOD
- RESULTS AND DISCUSSION
- SUMMARY, CONCLUSION AND RECOMMENDATION
- LITERATURE CITED
- APPENDICES