Pests
General recommendation: Seedlings in the nursery can be protected using mesh netting
or yellow sticky traps. After plants are in the field, regular surveillance and
spraying plant extracts are effective. Chemical pesticides should be used mainly
as a corrective measure. If possible, choose a pesticide that targets the specific
pest that is causing the damage, and avoid pesticides that kill beneficial
organisms. Choose pesticides that have short persistence, i.e., the effects
of which last only a few days. Chemical pesticides should be applied in the
evening, and if multiple applications are needed, rotate pesticides that have different
modes of action.
The major pests found to cause serious damage to chilli crop and their management
practices are detailed below:
Aphids (Aphis gossypii, Myzus persicae)
Aphids are small, succulent, pear shaped insects that vary in color from yellow
to green to black. Theses insects pierce leaves and suck the sap, causing
foliage to become distorted and often curled under. Aphids exude a sticky substance
that attracts ants and leads to the development of a sooty mold on plants. Aphids
are vectors to many viruses.
Control: Spraying dimethoate at 0.05% is effective for controlling aphids.
Broad mite (Polyphagotarsonemus latus)
Yellow or white, tiny, crab like insects known as mites suck plant juice near the
mid vein on the undersides of the leaves causing leaves to curl downwards and become
narrow. Most damage occurs between veins of young leaves. Corky tissue develops
on fruits.
Control: Use of tolerant cultivars, weed control, crop rotation, and spraying
acaricides such as dicofol helps to reduce mite infestation. Spraying dimethoate
at 0.05% or Spiromecifen 22.9 SC @ 96 g ai/ha or Fenpyroximate 5 EC @ 15 g ai/ha are
also effective for controlling broad mites.
It is also managed by the application of neem oil 5% and neem oil+ garlic emulsion 2%.
Thrips (Scirtothrips dorsalis,
Thrips palmi)
Thrips are very small insects that group together along the mid vein or along borders
of damaged leaf tissues. Thrips cause young leaves to curl upwards. Brown areas
develop between veins of both young and old leaves. Corky tissue develops on infested
fruits.
Control: Reduce thrip damage by controlling weeds, rotating crops, using predators
and parasites, and rotating insecticides. Dimethoate spray at 0.05 % is effective
for controlling thrips.
Tomato fruit worm (Helicoverpa armigera)
Tomato fruit worm feeds on flowers, pods and fruits of chilli. Larvae move from
one fruit to the next, destroying only small portions of each fruit. Damaged fruits
may drop, ripen prematurely, or become infected with disease. The entrance
hole near the pedicel develops a dark scar. Young larvae are light yellow and spotted.
Mature larvae are brown to gray in color with lengthwise stripes along
the body and are usually found inside the damaged fruits.
Control: Monitor closely for the larvae on plants and destroy them. Remove infested
fruits to reduce pest populations. Spraying any contact insecticides will help to
kill exposed larvae.
Mealy bug
Nymphs and adults of mealy bugs suck sap from the leaves, tender shoots, and the
fruits. Leaves show characteristic curling symptoms and heavy black sooty mould
may develop on the honeydew like droplets secreted by mealy bugs. When the fruits
are infested, it may lead to fruit drop or the fruits remain on the shoots in a
dried and shriveled condition.
Control: Spraying insecticides like dichlorvos (0.02%) or quinalphos (0.025%) with
fish oil rosin soap control the insect population. Unlike the adults, the crawlers
are free from waxy coating and therefore the crawler stage is the most effective
stage for spraying pesticides.
Root knot nematode (Meloidogyne
spp.)
Root knot nematode damages the root system resulting in the formation
of small galls on the roots. The infested plants become stunted and yellow. Severely
affected plants may wilt. This nematode has a very wide host range. Its eggs can
remain dormant for a few months. Warm temperatures and light sandy soils are conducive
for its development.
Control: Cultivating resistant varieties and crop rotation; flooded rice field in
particular greatly reduces nematode populations. Destroy alternate hosts harbouring
the nematodes. Ploughing during the fallow season will expose nematodes to sun and
predators. Soil fumigants or nematicides may also be used.
Diseases
General recommendations: Use high quality, pathogen free seeds and seedlings.
Cultivate resistant varieties in disease endemic areas. High plant density leads
to weak and susceptible plants, therefore use the proper plant density, both in
seedling production beds and in the transplanted field. Follow clean cultivation
practices, remove diseased leaves and seedlings promptly, and control weeds regularly.
Many pathogens spread through irrigation water, and therefore never allow irrigation
water from diseased field to enter disease free field. Prevent plants from being
overloaded with fruits. Crop rotation, particularly a rice-chilli rotation, helps
reduce disease and insect problems. Chilli crop should never follow other solanaceous
crops as these crops share many soil borne diseases. Do not plant chilli after sweet
potatoes, due to allelopathic effects. The following are some of the most common
diseases on chilli:
Damping off
This is a serious disease in the nursery. High soil moisture and moderate temperature
along with high humidity especially in the rainy season favour the disease. Two
types of symptoms are observed, viz., pre emergent and post emergent damping off.
The pre emergent damping off results in rotting of seed and seedling before emerging
out of soil, whereas in the post emergent damping off, seedlings after emergence
are infected near the collar region at ground level. The infected tissues become
soft and water soaked. The collar portion rots and ultimately the seedlings collapse
and die.
Control: For avoiding damping off of the seedlings in the nursery, sow the seeds
as thin as possible in raised beds prepared in the open area during summer months.
Spray nursery and main field with 1% Bordeaux mixture at monthly intervals during
rainy season.Soil solarisation of nursery beds for 30 days prior to sowing and seed
treatment with Trichoderma @ 5 g/kg seed is effective in managing the disease.
Bacterial wilt (Ralstonia solanacearum)
The initial symptom is wilting of lower leaves followed by a sudden and permanent
wilt of the entire plant without yellowing. Bacterial ooze streams out when cross
sections of the lower stem are suspended in water. It is more severe on tomato,
tobacco, potato and eggplant, but it can be very damaging to chilli. The
bacterium is found to survive in the soil for long periods. It gains entry through
natural root wounds or wounds created by insects, nematodes or implements. High
temperature and high soil moisture favour disease development.
Control: Using pathogen ree seedbeds to produce disease fee transplants and
fumigating seedbeds help to contain the diseases. Use raised beds to facilitate
drainage. Rotating with flooded rice, and other non usceptible crops provides limited
control. Crop rotation with brinjal, tomato, and potato should be avoided. Avoid
cultivation operations that damage roots. To avoid soil splash, the use of mulch
and furrow irrigation, rather than overhead irrigation, are preferred. Removal
and destruction of affected plants and use of disease resistant varieties like Manjari,
Ujwala or Anugraha in bacterial wilt prone areas help to reduce the disease
incidence. Before sowing, the seeds should be dipped in a solution of streptocycline
(1 g/ 40 litres of water) for 30 minutes.
Anthracnose (Collectotrichum
spp.)
Anthracnose may occur in the field or develop as a post arvest decay of chilli fruits.
Typically, symptoms first appear on mature fruits as small, water soaked, sunken
lesions that rapidly expand. The lesions may increase to 3-4 cm in diameter
on large fruits. Fully expanded lesions are sunken and range from dark red to light
tan. The disease may occur wherever chilli is grown under overhead irrigation or
rainfed conditions. The pathogens can be seed borne in chilli and persist in crop
debris and have a wide host range.
Control: Use seeds collected from anthracnose free fruit and treat seeds with a
fungicide. Hot water treatment at 520 C for 30 minutes is also recommended.
Crop rotation with non host crops and mulching to reduce soil splashing onto fruit
and flowers are also effective. Avoid overhead irrigation to reduce periods of wetness
on chilli fruit. Harvest fruits as soon as it ripens since anthracnose develops
more readily on mature fruits. Weed regularly and avoid injuring chilli fruit. Remove
and destroy infected plant debris. Avoid planting overlapping chilli crops nearby.
Apply protectant fungicides to plants starting when the first fruit is set.
Phytophthora blight (Phytophthora
capsici)
This disease can occur on chilli grown anywhere in the world, at any stage of growth,
and on all plant parts. The most common symptom is a stem or collar rot followed
by sudden wilting without foliar yellowing. Other symptoms include damping
off and tip blight of young seedlings; dried tan colored lesions on foliage, as
well as softened fruit.
Control: Since Phytophthora blight is soil-borne and more prevalent on
poorly drained soils, ensuring adequate drainage and following careful cultural
practices are important for providing good control. Practice crop rotation with
crops other than tomato, eggplant, and cucurbits for at least 3 years to reduce
the soil inoculum. Overhead irrigation, will encourage disease spread and should
be discontinued if the disease is present.
Aphid transmitted viruses
Chilli veinal mottle virus (ChiVMV), cucumber mosaic virus (CMV) and potato
virus Y (PVY) are the major viruses that are transmitted through aphids. Symptoms
vary, but generally these diseases show mosaic, mottled or deformed leaves. Plants
are stunted and the loss of marketable yield can be drastic.
Control: Use of resistant cultivars, and controlling aphid vectors by destroying
weeds, using insecticides, and using mesh netting to exclude aphids from seedlings
provide good control.
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