Disease management

DAMPING-OFF OF SEEDLINGS
(Pythium)
Symptoms: Infection occurs on stem at soil level. Initial symptoms are water soaked lesions on the soft stem tissue. The lesions expand leading to the collapse of seedlings. Generally the disease spreads through infected planting material, soil and water.

Management Soil-drench with Captaf (0.2%) or copper oxychloride (0.3%).

POWDERY MILDEW
(Leveillula taurica)
Symptoms: The disease first appears as tiny white spots on the under surface of the leaves and later turn into large irregular spots. Subsequently, the white powdery growth covers entire leaf on the undersurface. Yellowish spots appear on the corresponding infected portions on the dorsal surface of the leaves. Affected leaves tend to drop off prematurely.

Epidemiology: Alternating low and high temperature coupled with high humidity favours the disease spread.

Management : Spray Wettable sulphur (0.3%) or Tridemorph (0.1 %) or Hexaconazole (0.05%) or Dinocap (0.1 %) or Flusilazole (0.03 %) or Myclobutanil (0.1 %) at 10 -15 day intervals (2-3 sprays).

PHYTOPHTHORA BLIGHT
(Phytophthora capsici)
Symptoms: Initial symptoms are water soaked small dark green spots that enlarge and become bleached, as though scalded. Infected fruits initially develop dark, water-soaked patches that become coated with white mold and spores of the fungus. Fruits wither but remain attached to the plant. Seeds will be shriveled and infested by the fungus.

Epidemiology: Prolonged wet weather favours the disease spread.

Management:
1. Practice crop rotation with crops other than tomato, eggplant and cucurbits, for at least 3 years.
2. Avoid poorly drained fields for growing these crops.
3. Plant the crop on ridges, or on raised dome¬ shaped beds to provide better soil drainage.
4. Foliar application of Mancozeb (0.2%) or Copper oxychloride (0.3%), Copper hydroxide(0.2%) or Fosetyl-AI (0.2%) or Pre-packed mixture of Metalaxyl - Mancozeb (0.2%) or combination of Dimethomorph (0.1%) – Metiram (0.2%), Azoxystrobin (0.2%), Pyraclostrobin + metiram (0.2%), Fenamidone - Mancozeb(0.3%), Famoxadone - cymoxanil (0.1%), which gives good control.

ANTHRACNOSE
(Colletotrichum capsici, and C. gloeosporioides)

Symptoms: Anthracnose, also known as ripe fruit rot disease. Although the disease occurs mostly on maturing fruits, infections can occur on stem, petiole and leaves. Infection appears as sunken lesions on the fruit. The lesions may turn black with the formation of acervuli containing salmon-colored hyaline spore mass. Water-soaked spots on fruits with concentric rings, become dark and depressed, Harvest coincides with rain
Warm and humid weather are favourable conditions for disease

Epidemiology: The pathogen survives on infected seed and plant debris. High humidity and moderate temperature favour disease development.
Management :
1. Seed treatment with Thiram (0.3%) or Captan (0.3%).
2. Foliar application of Carbendazim (0.1 %) or Thiophanate methyl (0.1 %) or Propiconazole (0.1 %).
3.fruits harvest in rain free conditions, crop rotation, avoiding overhead irrigation, fungicides (chlorothalonilor mancozeb)

LEAF SPOT
(Cercospora capsici )

Symptoms: Oval or oblong spots with light grey centres on leaves, stalks and stem. Infected leaves drop off prematurely.

Epidemiology: The pathogen survives on infected seed and infected plant debris. Cool, humid conditions and moderate temperature favour the disease.

Management :
1. Seed treatment with Thiram (0.3%) and Captan (0.3%).
2. Foliar spray of Carbendazim (0.1 %) or Mancozeb(0.2%) or Carbendazim-Mancozeb (0.2%).

BACTERIAL WILT
(Ralstonia solanacearum)

Symptom: The pathogen is soil-borne in nature and mostly affects solanaceous crops. Initial symptoms of wilt occur in the younger leaves and slight yellowing occurs in older leaves. Wilted leaves maintain their green color and do not fall-off as the disease progresses. Under conditions favorable to the disease, complete wilt occurs. Wilting and death is accompanied by dark-brown internal discoloration of vascular elements.

Management :
1. Seed-treatment with Pseudomonas fluorescens before sowing.
2. Seedling-root dip with P.fluorescens and planting in green manure (sun hemp) amended soil.
3. Foliar application of antibiotics (Steptocycline 300 to 500 ppm).
4. Crop rotation with maize-sorghum-ragi or maize¬onion or garlic and paddy.

CHILLI LEAF - CURL DISEASE
(Chilli leaf curl virus, Begomovirus genus of Geminiviridae)

Symptoms: Symptoms consist of upward and downward curling of leaves. Leaf margins develop pale-green to yellow color, which extends into the inter¬veinal areas. Nodes and internodes are significantly reduced in size. Infected plants assume a bushy appearance, with severely stunted growth, look pale and produce more lateral branches. Fruits from infected plants are small and deformed. It is a single-stranded DNA virus.

Epidemiology: Field-spread occurs through white¬fly, an insect vector (Bemisia tabaci). This disease increases with increases in temperature and relative humidity. The virus mainly perpetuates on weed¬ hosts. Warm and dry weather favors disease-spread. In southern India, disease epidemics are more common during March-June, whereas under north Indian conditions, epidemics occur from June to October.

Management :
Cultural control
1. Growing the nursery under nylon-net cover (50 mesh)
2. Eradication of early-infected plants and weed ¬hosts from the field
3. Two rows of border-crop pings with maize, jowar, or bajra reduce disease-spread
Chemical control
1. Soil-application of Furadon @ 1.5 Kg ai/ha at the time of sowing.
2. Spray seedlings with Acephate (0.15%) or Monocrotophos (0.1 %) prior to transplanting.
3. Spray insecticides like Monocrotophos (0.15%), Acephate (0.15%) or Hostothion (0.1 %) at fortnightly intervals after transplanting, until the flowering stage.
4. Chemical spray, followed by neem seed kernel extract (2%), is also effective in rotation with insecticides.

CHILLI MOSAIC AND LEAF DISTORTION DISEASE
(Cucumber mosaic virus)

Symptoms: Symptoms are extremely variable depending on the variety/ hybrid and on weather conditions. Common symptoms are: initial chlorotic lesions, followed by light- and dark-green areas appearing as mosaic. At later stages, newly emerging leaves distort or transform into filiform or thin, elongated leaves. In severe cases, plants get stunted and produce less number of fruits. Fruits from infected plants are hard and brittle, full of seeds. Yellow streaks may also appear on fruits. The virus is an isometric particle of 28 nm size, has a genome of single-stranded multipartite RNA and belongs to the Cucumovirus group.

Epidemiology: The disease spreads by mechanical contact and also through seed and insect-vector aphids (Aphis gossypii, A. craccivora, Myzus persicae).

Management:
Nursery stage
1. Growing the nursery under nylon-net cover (40¬50 mesh).
2. Soilapplication of systemic insecticides like Furadon @ 1.0 Kg ai / ha at the time of sowing seeds in the nursery bed.
3. Prior to transplantation, seedlings should be sprayed with Acephate (0.15%) or Monocrotophos @ (0.15 %) or Dimethoate (0.2 %).
Main field
1. Sowing border crops like maize/ bajra/jowar, 15 days before transplanting the main crop.
2. Removal of early-infected plants from the field.
3. Spraying Acephate (0.15 %) or Hostothion (0.1 %) or Imdacloprid (0.05%); these chemicals should be used alternatively and should not be repeated continuously.
4. Spraying neem seed kernel extract (2 %) + sticker, 15 days after transplanting until fruit formation, at 10 days intervals.
5. Mulching with silver or black colored polythene mulch-sheet.
6. Growing virus tolerant varieties.

CHILLI NECROSIS DISEASE
(Groundnut bud necrosis virus, GBNV)

Symptoms: This disease is characterized by bronzing of young leaves, chlorosis, followed by necrotic ring spots. Necrotic spots appear under the growing tips and the entire twig dies back. In some cases, this leads to severe stunting and cessation of growth. Early-infected plants bear deformed, unevenly ripe fruits, while, fruits formed after late-infection show concentric rings. Sometimes, side-shoots proliferate and do not bear fruit. The pathogen is a tripartite, negative-stranded and single-stranded RNA virus.

Epidemiology: GBNV is transmitted by thrips insect vector (Thrips palmi) and also mechanically. The virus is not seed-transmitted. This virus infects many legumes and solanaceous crops in addition to several weed species. Weed-hosts such as Emilia, Cassia, and Acanthospermum also serve as reservoir-hosts for both the virus and the vector.

Management
Cultural practices
1. Raising seedlings under nylon nets (50 mesh).
2. Roguing out infected plants and weed-hosts.
3. Growing two rows of the border crop with maize/jowarlbajra 15 days before transplanting chilli.
Chemical control
The same as in tomato bud necrosi

CHILLI MILD MOTTLE AND MOSAIC DISEASE
(Pepper mild mottle virus and Tobacco mosaic virus)

Symptom: The disease is characterized by mild mottling with light green areas, interveinal chlorosis, mosaic and distortion of fruits, in some varieties/ hybrids the half portion of leaf will be pale yellow color. The disease generally does not affect the growth of the plant. This virus belongs to tobamovirus group, which are having a rod shaped particles measuring 670 to 710 nm in length with 18 nm diameter. They have single stranded RNA genome.

Epidemiology: These viruses are externally seed borne and spread in the field mainly due to contact and injury to the crop during cultural operations in the crop. The virus mainly survives in the outer seed coat and seldom in the endosperm.

Management
1. The main preventive measure to protect the viruses is to use virus free seed.
2. Seed borne infection can be prevented by soaking seeds in Calcium hypochlorite (5 %) for 15 minutes or Trisodium phosphate (10%) solution for 20-30 min and drying.
3. Raising seedlings under nylon nets (50 mesh).
4. Roguing out infected plants and weed-hosts.
5. Growing two rows of the border crop with maize /jowar/ bajra 15 days before transplanting chilli.