Integrated Pest Management in Chilli, Tomato, Onion and Potato crops

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. In the past five decades the use of chemical pesticides steadily increased from 2.2 g/ha of active ingredient (a.i.) in 1950 to the current level of 650 g/ha (which is a 300 fold increase). 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, chilli and other vegetables. Yet, despite several sprays, crop losses are inevitable. But continuous usages of insecticides on crops for the past fifty years have led to the following problems:

• Several pests have developed insecticide resistance
• Degradation of natural enemies
• Secondary pest outbreaks
• Occurrence of toxic residues in crops and products
• Inputs on plant protection have increased enormously.

Pesticide Residues

In general, about 50% of the pesticides that are applied to the crops reach the soil. The chemical residues find their way to the aquatic systems or get accumulated in the plant products. Chlorinated compounds are more persistent in nature than other organophosphorus, carbamate and pyrethroid compounds. The basic problem in our agriculture is the negligence of safety intervals after sprays and also the lack of residue monitoring in crops and their products. There are many reports confirming the presence of pesticide residues in the environment, food and in human beings. During the 1990s Indian agricultural exports were about 17% of the global total. However, later this experienced a decreasing trend largely due to the occurrence of pesticide residues and aflatoxins. It was evident from the international scenario that there are strict monitoring mechanisms in place for monitoring pesticide residues across the world, hence products from the developing world failed to qualify in the international markets. To overcome the present situation 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 chilli, 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 litres of water or fipronil @ 2 ml per litre.

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.

Management: Spray with miticides such as dicofol @ 5 ml per litre or wettable sulphur 3 grams per litre or Pegasis @ 1 gm per litre or Vertemic @ 0.5 ml per litre. 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.

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 litre or imidacloprid @ 1 ml in 3-4 litres 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 grownup larvae feed on leaves and fruits resulting in holes. Well grown Spodoptera larvae are nocturnal in habit and hide in the soil during the day time.

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 chloripyriphos) 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/litre, ie, 1 litre/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 litre or spinosad @ 0.3 ml per litre 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 litres of water or fipronil @ 2 ml per litre.
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 litres of water or fipronil @ 2 ml per litre.
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 litre or wettable sulphur 3 grams per litre or Pegasis @ 1 gm per litre or Vertemic @ 0.5 ml per litre.
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 litre (LE = Larval equivalent)
Management of pod borers at later stage	Fruiting stage	Setting poison baits for Spodoptera Spray indoxacarb @ 1 ml per litre or spinosad @ 0.3 ml per litre
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 litre) or spinosad @ 0.3 ml per litre
Important diseases and their management
Anthracnose	Green fruit stage	Thiophonate methyl 1 g per litre Mancozeb 2.5 g per litre Tilt 1ml per litre, Antrcol 2g per litre
Powdery mildew	Flowering and fruiting stage	Dinocap 1 ml per litre, wettable sulfur 3g per litre

Note: These recommendations are for high volume sprayers. If low volume sprayers such as power sprayer are used, double the recommended dose.

Do’s and Don’ts in plant protection
Do’s	Don’ts
Follow the crop based threshold Monitor the crop at regular intervals for pests and diseases Follow recommended dosage Always use protective clothing Strictly follow safety periods prescribed for different chemicals. Use appropriate equipment Always use selective chemicals Augment natural enemies	Do not use chemical pesticides indiscriminately–calendar basis, mixtures, overdose; when natural enemies are active Do not spray chemicals when there is insufficient pest population Do not eat/smoke while handling pesticides Do not keep chemicals accessible to children/pets Do not mix biopesticides with chemicals