DISEASES OF ECONOMIC CROPS

REPRT ASSIGNMENT (YEAR TERM)

DISEASES ON CHILLI (Capsicum annum L.)

Jatu Barmawati (5410001273)

ANTRACNOSE

( Colletrotichum capsici, Colletotrichum gloeosporioides, Colletotricum acutatum

Colletotrichum coccodes )

1. Economic importance

Anthracnoses (from anthrax = carbon = black) are caused by fungi that produce conidia

within black acervuli. Antrachnose can attack chilli from all growth stage from pre-

harvest until post-harvest stage. This pathogen reported can make 84% crop losses when

rainy season and develop in high humidity after fruits started to ripen. This diseases

caused by many species of Colletotrichum, Colletrotichum capsici, Colletotrichum

gloeosporioides, Colletotricum acutatum Colletotrichum coccodes. This fungi have

teleomoph as Glomerella cingulata an include in Deutromycetes and Acomycetes fungi.

2. Symptoms

The disease appears as small circular spots that coalesce to form large elliptical spots on

fruits and leaves. Under severe conditions, defoliation of affected plants occurs. The

disease has been observed to occur in three phases, they are: (i) Seedling blight or

damping off, ii) Leaf spot and die back, and (iii) Anthracnose or fruit rot.

Source : Antrachnose Diseases of Chilli Pepper Technical Bulletin, 2009.

The disease is characterized by the appearance of small black circular spots on the skin of

the fruits that spread in the direction of the long axis, thus becoming more or less

elliptical. As the infection progresses, the spots get either diffused and black, greenish or

dirty grey in color or they are markedly delimited by a thick and sharp black outline

enclosing a lighter black or straw colored area. In some cases, the lesions are brown, and

then turn black from the formation of setae and sclerotia. Severe infection results in

change of fruit colour from red to straw or white. Numerous acervuli are scattered on the

discoloured area of the infected fruit. When a diseased fruit is cut open, the lower surface

of the skin is covered with minute, spherical, black somatic masses or sclerotia of the

fungus. A mat of fungal hyphae covers the seeds. Such seeds turn rusty in color. Affected

fruits are deformed, white in color and lose their pungency. Ultimately, the diseased fruit

shrivels and dry up.

Green fruit may also be infected but symptoms will not appear until the fruit ripens at

harvest time. Such an infection is called latent. Young fruit infected by C. acutatum can

have visible symptom development.

3. Host

Primary host of this pathogen is chili, and the alternative host is another Solanaceae and

weeds.

4. Life cycle

Source : Agrios, 2005

5. Pathogen survival

The fungus survives in and on seeds. Anthracnose is introduced into the field on infected

transplants or survives between seasons in plant debris or on weed hosts. Alternative

hosts include other Solanaceae (tomato, potato, eggplant).

Fruits are infected when spores of the fungus or infested debris are rain splashed onto

chilli plants. New spores are produced within the infected tissue and are then dispersed to

other fruits.

6. Diseases dissemination and development

Infection usually occurs during warm, wet weather. Temperatures around 27°C is

optimum for disease development, although infection occurs at both higher and lower

temperatures. Severe losses occur during rainy weather because the spores are washed or

splashed to other fruit resulting in more infections. The disease is more likely to develop

on mature fruits, although it can occur on immature fruits as well.

The disease causes serious losses to young shoots, flowers and fruits under favorable

climatic conditions of high humidity, frequent rains and a temperature of 24-32oC. It is

also affects fruits during storage

Distribution map

Source : http://www.plantwise.org/default.aspx?

site=234&page=4393&speciesID=10923&dsID=14893

7. Detection or diagnosis

Diagnose

Collect the plant or fruit from the field that has antrachnose symptoms. Make a

cross section between infected and health area. Look under microscope and

rechecked and compare the fruiting body or spore with the literature.

Make the isolate from the specimen, growth it in the media and checked the result

by take the spore and observed under the microscope.

8. Control and management

The control of Antracnose diseases depends on the use of disease-free seed grown in arid

areas or use of treated seed; crop rotation of hosts; use of resistant varieties when

available; removal and burning of dead twigs, branches, and fruit infected with the

fungus in woody plants; and, finally, spraying with appropriate fungicides.

Hot water treatment is recommended to destroy seed-borne fungi. Soak seed at

52°C for 30 minutes. Following treatment, plunge the hot seeds into cold water, dry

on paper, and dust with thiram. Freshly harvested seed withstands heat treatment

better than one or two-year-old seed.

Use resistant cultivar

IIHR, Bangalore, TNAU, Coimbatore, and PAU, Ludhiana, have developed

resistant varieties for anthracnose disease viz., IIHR 275-13-5, IIHR345-6, IIHR

332 -109, CC4, Ujwala, CA 874. S- 20-1, Lorai and BG-1.

Crop rotation of hosts

Rotate with non solanaceous crops for three years. Use mulch to reduce soil splash

on to fruit and lower leaves. Minimize or avoid overhead irrigation to reduce

periods of wetness on pepper fruit. Harvest fruit as soon as it ripens since

anthracnose develops more readily as the fruit ages. Weed regularly and avoid

injuring pepper fruit. Allow infested crop debris to decompose completely by deep

plowing of crop residues before planting again. If only a few plants are affected by

the disease, these can be removed from the field and disposed of. Avoid planting

overlapping pepper crops nearby.

Trees may be sprayed twice with Bavistin (0.1%) at 15 days interval during

flowering to control blossom infection. Spraying of copper fungicides (0.3%) is

recommended for the control of foliar infection.

Biological control

Antagonistic Pseudomonas fluorescens as seed treatment and as well as spray

treatment @108 CFU.g-1 were found to be effective against C. capsici

Trichoderma species are able to effectively control C. capsici infection in chilli.

FROG EYE SPOT ( Cercospora capsici )

http://agropedia.iitk.ac.in/?q=content/chilli-cercospora-leaf-spot

1. Symptoms

Circular spots appear with a light gray center and a reddish-brown margin, growing up to

1 cm in diameter. Spots later become tan with a dark ring and a yellowish halo around the

ring, resulting in a “frog-eye” appearance. Under conditions of high humidity, and using

a good high magnification hand lens, thin, needle-like spores may be seen in the center of

the spots arising from small black fungal tissue. The affected centers of lesions dry and

often drop out as they age. When numerous spots occur on the foliage, the leaves turn

yellow and may drop or wilt. Defoliation is often serious, exposing fruits to sun scald.

Spots also develop on stems and petioles but they are oblong rather than circular. Fruit

are not infected.

2. Host

Primary host is chili, it also can survive on weeds and another Solanaceae

3. Life cycle

Primary source of inoculum: Dormant mycelium in infected plant debris, infected seeds

and volunteer plants.

Secondary source of inoculum: Air born spores

4. Pathogen survival

The fungus survives in or on seed, and as tiny black fungal tissue known as stromata in

old affected leaves in the soil. Spores will survive in infected debris for at least one

season.

5. Diseases dissemination

Foliar infection occurs by direct penetration of the leaf. The fungus spores require water

for germination. and penetration of the host; however, heavy dew appears to be sufficient

for infection. The disease is most severe during periods of warm temperatures; for

example, 20–25°C during the day and excessive moisture (either from rain or overhead

irrigation). Fungal growth is limited if the temperature is < 5°C or > 35°C. The fungus is

spread by splashing water, wind-driven rain, wind, on implements, tools, workers, and by

leaf-to-leaf contact. It is not known whether the fungus will infect solanaceous weeds.

6. Control and management

Rotate crops using a two-year rotation period. Control Solanaceous weeds during the

rotation period. Check older plants carefully for the first incidence of the disease

particularly after extended periods of leaf wetness and warm temperatures. If symptoms

appear, apply a protectant fungicide as soon as possible. Resistant varieties are available.

Check with your local extension agent for fungicides and varieties that may be used

effectively in your region.

Spray twice at 10-15 days interval with Mancozeb 0.25% or Chlorothalonil (Kavach)

0.1%.

RALSTONIA/BACTERIAL WILT ( Ralstonia solanacearum )

Source : http://www.cotometg.es.tl/BACTERIAS-EN-CHILE.htm

1. Symptoms

R. solanacearum is a Gram-negative rod, 0.5-1.5 µm in length, with a single polar

flagellum. The youngest leaves are the first to be affected and have a flabby appearance,

usually at the warmest time of day. Wilting of the whole plant may follow rapidly if

environmental conditions are favourable for the pathogen. Under less favourable

conditions, the disease

develops less rapidly, stunting may occur and large numbers of adventitious roots are

produced on the stem. The vascular tissues of the stem show a brown discoloration and, if

the stem is cut crosswise, drops of white or yellowish bacterial ooze may be visible

2. Host

Solanaceae

3. Life cycle

4. Pathogen survival

5. Diseases dissemination

6. Detection or diagnosis

7. Control and management

POWDERY MILDEW (Leveillula taurica)

Source : http://vegetablemdonline.ppath.cornell.edu/NewsArticles/PepperyPowdery.htm

1. Symptoms

Shedding of foliage, white powdery growth on lower side of leaves. Chlorotic

blotches or spots appear on the upper leaf surface.

When lesions are numerous they may coalesce resulting in a general chlorosis of

the leaves.

The disease progresses from the older to younger leaves and shedding of foliage

is prominent symptom.

2. Host

Chili, tomato, and weeds

3. Life cycle

4. Pathogen survival

The fungus predominately infects leaves, but it can occasionally be found attacking fruit.

5. Diseases dissemination

Disease occurs in warm climates both dry and humid. Leaf shedding is more pronounced

at low humidity. The disease is favored by warm temperatures (from 65-95o F). Although

high humidity favors germination of spores, infection can occur during periods of high or

low humidity. The fungus reproduces rapidly under favorable conditions. Wind-

disseminated spores cause secondary infections, which help spread the disease. The

disease is most severe on older leaves just prior to fruit set, but can occur at any time

throughout the season if environmental conditions are favorable. Severe infections early

in the season can result in heavy yield losses.

6. Detection or diagnosis

Look for the symptoms, make the cross section and observed under the microscope, it

can’t growth in PDA because it is parasite obligate.

7. Control and management

Spray Wettable sulphur 0.25% or Dinocap (Karathane) 0.05%. Spray thrice at 10-15 days

interval with 1ml Dinocap or 2g Wettable Sulphur per litre of water. Before flowering,

dusting 8-10 kg Sulphur per acre is also useful.

FUSARIUM WILT ( Fusarium oxysporum f. sp. vasinfectum )

http://www.infonet-biovision.org/print/images/87/pests

1. Symptoms

Fusarium wilt is characterised by wilting of the plant and upward and inward rolling of

the leaves. The leaves turn yellow and die. Generally appear localised areas of the field

where a high percentage of the plants wilt and die, although scattered wilted plants may

also occur. Disease symptoms are characterised by an initial slight yellowing of the

foliage and wilting of the upper leaves that progress in a few days into a permanent wilt

with the leaves still attached. By the time above - ground symptoms are evident, the

vascular system of the plant is discoloured, particularly in the lower stem and roots.

2. Host

Only in chili

3. Life cycle

4. Pathogen survival

The fungus can invade a plant either with its sporangial germ tube or mycelium by

invading the plant's roots. The roots can be infected directly through the root tips, through

wounds in the roots, or at the formation point of lateral roots.

5. Diseases dissemination

High temperatures and wet soil conditions favour disease development. Disease is most

likely occur in poorly drained soils. Hence, provision of drainage is necessary to control

this disease to some extent.

Fusarium wilt diseases are commonly associated with root knot nematodes. The Fusarium

infects through wound sites made by the nematode.

6. Control and management

Use of wilt resistant varieties.

Drenching with 1% Bordeaux mixture or Blue copper or Fytolan may give

protection.·

Seed treatment with 4g Trichoderma viride formulation or 2g Carbendazim per kg

seed is effective. Mix 2kg T.viride formulation mixed with 50kg FYM, sprinkle

water and cover with a thin polythene sheet. When mycelia growth is visible on

the heap after 15 days, apply the mixture in rows of chilli in an area of one acre.

DAMPING OFF ( Phytium spp. and Phytophthora sp. )

1. Symptoms

Seed may rot or the seedlings may be killed before they emerge from the soil. Stem of

young seedlings may also be attacked after emergence showing water soaking and

shrivelling of stem which fall over and die.

In nursery the disease may appear in patches in 2-4 days, the entire lot of seedling may be

destroyed.

2. Host

3. Life cycle

4. Pathogen survival

Fungus is mainly soil - borne.

5. Diseases dissemination

Disease is most damaging on moist soils with poor drainage.

It requires humidity in the range of 90-100 percent and a soil temperature nearer 20oC.

When there is sufficient moisture in the soil, it germinates and produce mycelium which

later forms the asexual stage of reproduction. The fungus is capable of living for many

years in soil.

6. Control and management

Follow cultural practices such as thin planting (600 - 750g seed per cent) on

raised seedbeds.

Use of light textured soils provides better drainage and aeration.

Use of well decomposed manure.

Soil sterilization by drenching the soil 4" deep with Formaldehyde diluted 50 times with

water or with some other effective chemical soil sterilant.

Soil drenching with 1% Bordeaux mixture or 3g Copper Oxychloride like Blue copper

per litre of water at 12 and 20 days after sowing is also useful.

Seed treatment with 3g Captan or Thiram per kg seed

Seed treatment with 4g Trichoderma viride formulation combined with 6g Metalaxyl is

highly effective.

BACTERIAL SPOT (Xanthomonas campetris pv. vesicatoria )

Source : http://www.cotometg.es.tl/BACTERIAS-EN-CHILE.htm

1. Symptoms

The leaves exhibit small circular or irregular, dark brown or black greasy spots. As the

spots enlarge in size, the centre becomes lighter Surrounded by a dark band of tissue.

The spot coalesce to form irregular lesions. Severely affected leaves become chlorotic

and fall off.

Petioles and stems are also affected. Stem infection leads to formation of cankerous

growth and wilting of branches.

On the fruits round, raised water soaked spots with a pale yellow border and produced.

The spots turn brown developing a depression in the centre wherein shining droplets of

Bacterial cozen may be observed.

2. Host

Only on chili

3. Life cycle

4. Pathogen survival

5. Diseases dissemination

6. Detection or diagnosis

7. Control and management

Seed treatment with 0.1% mercuric chloride solution for 2 to 5 minutes is

effective.

Seedlings may be sprayed with Bordeaux mixture 1. Per cent or copper

oxychloride 0.25%.

Spraying with streptomycin should not be done after fruits begin to form.

Field sanitation is important. Also seeds must be obtained from disease free

plants.

VIRUS (CMV, TSWV, TYLCV, PSTVd)

1. Control and management

Control measures are not known for majority of viral diseases.

Hence, mechanical, cultural methods are mostly recommended.

The infected plants should be uprooted and burnt or buried to avoid further

infection.

Avoid monoculture of chilli crop.

Selection of healthy and disease - free seed.

Suitable insecticidal sprays reduce the incidence of viral diseases, since majority

of viral diseases are transmitted by insect vectors.

Soaking seeds in a solution containing 150 g Trisodium orthriphosphate per litre

of water for 30 minutes inhibits seed - borne inoculum.

Treated seed should be washed with fresh water and dried before sowing.

Nursery beds should be covered with nylon net or straw to protect the seedlings

from viral infection.

Raise 2-3 rows of maize or sorghum as border crop to restrict the spread of aphid

vectors.

Apply Carbofuran 3G @ 4-5 Kg/acre in the mainfield to control sucking complex

and insect vectors selectively.

If it is not possible spray the crop with systemic insecticides. Like Monocrotophos

1.5 ml or Dimethoate 2ml of Acephate 1g per litre of water.

Collect and destroy infected virus plants as soon as they are noticed.

NEMATODE ( Meloidogyne sp. )

1. Symptoms

They normally cause stunting and poor yield and sometimes cause obvious yellowing.

Severe infection by nematodes sometimes causes wilting and plant collapse under stress

conditions.

2. Host

The majority of plant parasitic nematodes affect a wide range of hosts, but the degree of

susceptibility varies depending on the host plant

3. Life cycle

4. Pathogen survival

Nematodes can survive in the absence of the host in a dormant state. In dry periods they

move down deeper in the soil profile.

5. Diseases dissemination

Nematodes cannot swim. They move in soil or plant roots by ‘wriggling’ with a snake-

like movement and pressing against the soil particles or plant tissue. They can be carried

in moving irrigation water, but in still water they sink to the bottom. They can move in all

directions through wet soil in search of host roots.

6. Detection or diagnosis

Root knot nematode can be diagnosed in the field by obvious root galls. They are more

obvious using a dissecting microscope. If root lesion nematodes are suspected, they can

be seen under the microscope more easily if infected rootlets are stained.

7. Control and management