Insect pests and diseases are among the major constraints to enhancing production and productivity of vegetable crops. In recent years, farmer incomes have been declining particularly due to the rising costs of inputs for plant protection. Plant protection in the present day is mainly oriented towards chemical control. In India, insecticides are used much more than other pesticides such as fungicides and herbicides. In some areas, farmers are applying 25 to 40 chemical sprays to the crop particularly in commercial crops such as cotton, chili, and other vegetables. Yet, despite several sprays, crop losses are inevitable. But continuous usage of insecticides on crops for the past fifty years has led to the problems like several pests have developed insecticide resistance, Degradation of natural enemies, Secondary pest outbreaks, Occurrence of toxic residues in crops and products and inputs on plant protection have increased enormously. To overcome these problems, there is a need for development and adoption of Integrated Pest Management (IPM) approaches in various crops to satisfy the export requirements with better environment and health.
Among various insect pests, thrips, aphids, mites and fruit borers in chili, fruit borers and white flies in tomato and thrips in onion are of prime importance. Though insect pests are of minor importance in potato, foliar diseases are of importance. Also, though the pest species vary considerably across these crops, the general management strategies are similar.
Thrips
These minute and soft bodied insects are polyphagous, cosmopolitan, and occur throughout the year. Both nymphs and adults lacerate the leaf tissues and feed on the oozing sap. Usually, young leaves are preferred, but buds and flowers also get infested. The infested leaves become shortened, curl upwards, and crinkle. Under severe infested conditions the leaves shed and hence plant growth is affected. Buds, when infested, become brittle, petals of the flowers become brown and drop off. Infested fruit have light brown scars.
Management: Seed treatment with imidacloprid (Gaucho) @ 5 grams per kg seed. In the field, spray with imidacloprid @ 1 ml in 3-4 liters of water or fipronil @ 2 ml per liter.
Mites
These are tiny insects that live on tender foliage, buds and fruits by sucking the plant sap. These are found mostly on the lower surface of leaves in a protective web. Under severe infestation of chillies the leaves curve downwards and fruit turns brownish with hardened skin.
Pest Management: Spray with miticides such as dicofol @ 5 ml per liter or wettable sulphur 3 grams per liter or Pegasis @ 1 gm per liter or Vertemic @ 0.5 ml per liter. Use overhead irrigation with sprinklers for effective management of mites wherever possible.
Aphids
These tiny insects can infest the crops at any time during the growing season. They look like minute dark specks and tend to gather around the shoot tips, flower buds and all over young foliage. Aphids also leave sticky excreta on leaves that they have been feeding on, which could help in the development of fungal molds. Aphid infestation results in stunted or deformed growth.
Pest Management: An easy solution is to spray a very weak soap solution. This works well, although frequent application may affect crop growth. Ladybird beetles and hover flies are natural predators of aphids. Trying to attract them into these fields is the best way to naturally control the pests. Planting bright flowers such as marigolds around the chilli and tomato plots is a novel way to attract these natural enemies. In case of severe infestation, application of dimethoate @ 2 ml or acephate @ 1 gram per liter or imidacloprid @ 1 ml in 3-4 liters can effectively manage aphids.
Pod borers
Pod borers are highly polyphagous and cosmopolitan in distribution. These normally start infesting chilli and tomato crops around flowering time. Young larvae feed on leaves by scraping chlorophyll, while grown-up larvae feed on leaves and fruits resulting in holes. Well grown Spodoptera larvae are nocturnal in habit and hide in the soil during the daytime.
Pest Management: Installation of pheromone traps for Spodoptera litura and Helicoverpa armigera are of immense value in monitoring this pest. Planting sunflower along the borders can attract ovipositing moths, thereby saving the main crop from infestation. Use of poison baits (8:1:1 bran, jaggery, and chlorpyriphos) and placing them close to the plants proved effective in controlling immigrating Spodoptera caterpillars (25 kg bait is sufficient for one ha). Foliar spray with Bacillus thuringiensis (Bt) at recommended dose (for example, a product such as dipel can be applied @ 4 ml/liter, ie, 1 liter/ha with power sprayer) at early stage of pod borer infestation can provide effective control. In case of epidemic situations, application of indoxacarb @ 1 ml per liter or spinosad @ 0.3 ml per liter will be effective. Also, for Spodoptera and Helicoverpa, application of nuclear polyhedrosis virus (NPV) @ 500 LE per ha at the early stage of the pest infestation proved to be an effective control.
IPM module
|
Activity |
Stage of crop |
Management option |
|
Seed treatment |
Sowing time |
Imidacloprid (Gaucho) @ 5 grams per kg seed. |
|
Management of sucking pests |
Nursery |
Imidacloprid @ 1 ml in 3-4 liters of water or fipronil @ 2 ml per liter. |
|
Sowing trap crops |
At the time of transplanting |
Sunflower and marigold as border crop for chilli and tomato. |
|
Installation of pheromone traps and bird perches |
At the time of transplanting |
Two traps per location for each species About 25 perches/ha. |
|
Management of thrips in main crop |
Transplanting to one month before harvest |
Overhead irrigation with sprinklers wherever possible Imidacloprid @ 1 ml in 3-4 liters of water or fipronil @ 2 ml per liter. |
|
Management of mites |
In the nursery and main crop |
Overhead irrigation with sprinklers wherever possible. Spray one of these chemicals once in the nursery and second time in the main crop – dicofol @ 5 ml per liter or wettable sulphur 3 grams per liter or Pegasis @ 1 gm per liter or Vertemic @ 0.5 ml per liter. |
|
Management of fruit borers at initial stage |
Flowering stage |
Application of neem fruit powder extract @ 25 kg ha-1 NPV @ 500 LE/ha, Bt 4 ml per liter (LE = Larval equivalent) |
|
Management of pod borers at later stage |
Fruiting stage |
Setting poison baits for Spodoptera Spray indoxacarb @ 1 ml per liter or spinosad @ 0.3 ml per liter |
|
Arresting immigrating Spodoptera |
Crop maturity stage |
Erecting polythene fence around the field (4 inches above ground) |
|
Management of pod borers during crop maturity |
During crop maturity (few weeks before harvest) |
NPV @ 500 LE/ha, Bt (dipel @ 4 ml per liter) orspinosad @ 0.3 ml per liter |
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