गेहूँ में उभरती कीट समस्या एवं उनका प्रबंधन
Wheat is the second most important staple food crop in India providing nutrition to millions of population. India harvested a record wheat production of 109.5 million tonnes with productivity of 34.24 q/ha in 2020-21. Even though hundreds of pests were reported on wheat crop worldwide, it was considered pest free crop in India till late sixties. But due to changes in climatic conditions, production conditions, cropping patterns and use of new agro techniques resulted in several outbreaks of sporadic pests in wheat in India.
Impact assessment of different pests on wheat crop performance is significant in making proper management decision. Termites, aphids, shootfly, armyworm, American pod borer, Gujhia weevil, brown mite, pink stem borer, thrips and rodents are now considered as the major pests of wheat in India. Besides this stored grain pests like khapra beetle, lesser grain borer, rice weevil etc also cause significant losses in wheat.
1. Termites
About 16 species of termite have been found to damage wheat crop in India, of these two species viz., Odontotermes obesus and Microtermes obesi were major species which caused significant yield losses ranging from 43 to 80 per cent. Termites are widely distributed in the northern India, central India and some pockets of peninsular India. They are highly polyphagous and are found to damage many agricultural crops. Termite attack is more in those fields where un-decomposed farmyard manure is applied before sowing. Erstwhile termites were known to be serious pests of rain fed wheat but now they are infesting irrigated wheat also.
Nature of Damage:
Termites damage the crop soon after sowing and sometimes near maturity. They feed on roots, underground portion of stem, even dead tissues of plants feeding on cellulose. The severely damaged plants dry up completely and are easily pulled out. Patchy gaps are formed due to the death of seedlings resulting in poor or uneven plant stand. In case roots are partially damaged, the plants show yellowing. Damage due to termite may lead to poor germination in seeds.
Integrated pest management
Cultural
- Destruction of crop residues
- Deep summer ploughing of field to destroy termites’ mounds and tunnels and expose them to sunlight and predators.
- Application of fully decomposed farm yard
Chemical
- Seed treatment with Thiamethoxam 70 WP @ 1g or Chlorpyrifos 20% EC @ 4.5ml or Fipronil 5 FS @ 6 g per Kg of seed
- If the termite damage is noticed in the standing crop, apply Chlorpyrifos 20 EC @ 3 litre mixed in 50 kg of soil per hectare as soil application.
2. Aphids
Aphids are small, soft-bodied, pearl-shaped insects that breed at a fast rate during cold weather. About nine species of aphids are reported to infest wheat in India and among them, Rhopalosiphum padi, R. maidis and Sitobion miscanthi are the major ones.
Nature of Damage:
Among the three species, Rhopalosiphum padi is more dominant on foliar parts, stems and leaves while Sitobion miscanthi confined to the leaves and ear heads. The third species, Rhopalosiphum maidis infest on leaf whorls.
Aphid colonize on leaves, leaf sheath, flag leaf and in the spikelets of the ear heads. The nymphs and adults suck the sap from the plants, particularly from their ears. Due to their rapid multiplication within a few days, they usually cover the entire surface of the shoot leading to yellowing, curling and subsequent drying of leaves, which ultimately leads to reduction in number and size of ear heads. Honey dew secreted by the aphid encourages black sooty mould development on leaves that leads to 20-80% damage by interrupting the process of photosynthesis. The high populations of aphids at the ear head stage can cause substantial losses in yield. They also act as vectors of many viral diseases like barley yellow dwarf virus.
Integrated pest management
Cultural
- Avoid late sowing of crop.
- Avoid use of excess nitrogenous fertilizers.
- Plant tall border crops like maize, sorghum or millet to reduce pest population.
Biological
- Conserve the natural population of Aphelinus, lady bird beetle, Syrphid fly (Syrpus balteatus), Chrysopa (Chrysoperla carnea), preying mantids and some parasitic wasps to suppress the aphid population.
- Avoid spraying broad spectrum insecticides for the control of target pest
- Intercropping with legumes and ornamental flower’s plant can facilitate the conservation of natural enemies.
Chemical
- Chemical insecticides should only be applied if the insect population crosses the economic threshold level (ETL). ETL for aphids is 5 aphids per ear head.
- At the initial stage of infestation, spraying of borders of field with insecticide will help in reducing the aphid population and also in conservation of bioagents inside the field.
- As the colonizing of aphids starts, spray the crop with Imidacloprid 200 SL @ 40ml or Thiamethoxam 25% WG @ 20 g or Quinalphos 25% EC @ 400 ml per acre.
3. Army worm
Army worm (Mythimna separata Walker) is prevalent mostly in the warmer climates of central India and to some extent in northern plains. The larvae generally attack the plant during the night or early in the morning. In wet and humid weather, they may feed during day time also. The insect attack is observed in rice-wheat cropping system and they survive during summer on the subsequent crops like rice and also continue to exist in rice stubbles before wheat crop comes in the field.
Nature of damage
The attack is normally in the early stages of the crop. Young larvae feed on tender leaves, chewing from the edges to the midrib and then feeding inside the stem causing complete defoliation of the plant. They hang upside down from the slender bristles on the head (awns) and feed on the tips of developing wheat seeds leading to yield loss. Severe infestation leads to ceasing of plant growth leaving only stalk in the field. After destroying crop of one field, they move to the other crops.
Integrated pest management
Cultural
- In endemic areas, avoid crop rotation with host crops such as rice, maize etc.
- Destroy the alternate hosts i.e.Timothy grass (Phleum pratense).
- Avoid excess use of nitrogen fertilizer as it attracts the higher population of armyworm.
- Flooding of the field when the pest population is in the pupal stage.
- Avoid late sowing of wheat crop.
Biological
- Natural enemies like Cotesia ruficrus, Coccinellids, Braconid wasp, green lacewing, dragon fly, spider, robber fly, reduviid, praying mantis, red ants can be helpful for controlling the pest.
- Erect bird perches @ 10/acre can increase predation by insect-predatory birds.
Chemical
- ETL for armyworm is 4 - 5 larvae per metre row.
- Spraying Quinalphos 25 EC 800 ml per acre. Alternatively, spraying of Emamectin benzoate @12.5 g a.i/ha or Chlorantraniliprole @ 37 g a.i./ha
4. Pink stem borer
Pink stem borer, Sesamia inferens (Walker) is originally a pest of rice but became an established pest of wheat due to adoption of rice- wheat cropping patterns. In India, the pest has been reported from Rajasthan, Odisha, Uttranchal, parts of Sikkim and Manipur, Chhattisgarh, Punjab, Himachal Pradesh and Tamil Nadu. In the last two to three decades, its incidence has been increasing in India.
Nature of damage
It generally attacks the wheat crop at seedling stage. The larva bore in to the stem of young plant, resulting in the drying up of the growing point and formation of 'dead heart'. Sometimes the bottom internodes show circular ring like cuts. Severe damage causes the stem to break. At the ear emergence stage, due to its attack 'white ears' are produced which have little or chaffy grains.
Integrated pest management
Cultural
- Avoid crop rotation with rice.
- Removal or destruction of the crop stubbles
- Ploughing and flooding field is also effective in killing the larvae.
Biological
- Natural enemies of pink borer are Parasitoids: Apanteles, Tetrastichus, Telenomus, Trichogramma japonicum ,T chilonis, Bracon etc. and Predators: Spiders, drynids, water bugs, mirid bugs, damsel flies, dragonflies, meadow grasshoppers, staphylinid beetles, carabids, coccinellids etc.
- Avoid the spray of broad spectrum insecticides and using lowest rate of insecticides for the control of target pest can facilitate the conservation of natural enemies.
- Erect bird perches @ 10/acre can increase predation by insect-predatory birds.
Chemical
Need based spray of Quinalphos 25 EC 800 ml per acre.
5. Shootfly
Wheat shootfly (Atherigona naquii and A. oryzae) attacks in early and late sown crop. It has been recognized as a regular pest in major wheat growing states like Rajasthan, Gujarat, Madhya Pradesh, Uttar Pradesh, Delhi, Haryana and Punjab.
Nature of damage
Pest attack occurs one week to one month after wheat seed germination. The maggots bore into the shoot of young plants leading to drying of tillers resulting in formation of dead hearts. With the death of the tiller, the infected plant produce side tillers and in cases of severe infestation the plant gives a bushy appearance.
Integrated pest management
Cultural:
- Deep summer ploughing to expose soil to solar radiation.
- Avoid late sowing of crop and if crop is late sown, Increase the seed rate i.e. 120-130 Kg per hectare
- Always use well rotten manures.
- Apply recommended dose of fertilizers
- Fish meal traps can be used for monitoring the population build-up of shoot fly
Chemical:
- spray the crop with Imidacloprid 200 SL @ 40ml
6. Brown wheat mite
The brown wheat mite, Petrobia latens Muller is cosmopolitan pest of wheat and it was first reported from Madhya Pradesh in 1961. It is a pest of drier areas and is a serious problem under rainfed condition but its incidence in the irrigated crops also has been reported. Brown wheat mites feed during the day and spend the night in the soil.
Nature of damage
The nymphs and adults suck the sap from leaves, leaf sheath, green stem and spikes. Minute whitish specks appear on lower leaves which extends further upwards. Leaf become yellow and start drying from tip downwards. Web like structures may also be produced on the leaves. The plants become stunted, produce less earheads and shriveled grains. Mite also act as vector of Barley yellow streak mosaic virus disease.
Integrated pest management
Cultural
- Crop rotation of wheat with a non host plant
- Deep ploughing
Biological
- Predators like Oligota, Anthrocnodax occidentalis, Feltiella minuta etc., Green lacewings (Mallada basalis and Chrysoperla zatrowii sillemi), lady bugs etc can be checked the population growth of the pests. Besides this, some predatory mites like Amblyseius alstoniae, Phytoseiulus persimilis etc. can also helpful to control the pest.
- Conserve the natural enemies by growing flowering plants.
Botanical
- Spraying of neem formulations i.e. neem oil (3%) 0r NSKE (5%) can be effective for the control of pest.
Chemical
- Quinalphos 25 EC @ 640 ml per acre and if necessary repeat the spray after 15 days.
7. American pod borer
Pod borer, Helicoverpa armigera Hubner is a sporadic pest of wheat. The incidence is high in fields where wheat follows cotton. It is found mostly in northern and central parts of India, affecting gram, lablab, safflower, chillies, groundnut, tobacco, cotton, wheat etc.
Nature of Damage
The young larvae feed on the leaves, whereas the grown larvae feed directly on the grains in the ear heads. Internal tissues are eaten severely and completely hollowed out.
Integrated pest management
Cultural control:
- Crop rotation of wheat with non host plant
- Intercropping wheat with cowpea, onion, maize, coriander, urdbean in 1:2 ratio.
Biological control:
- Parasitoids likeTricogramma chilonis, Tetrastichus, Chelonus spp., Telenomus spp. (egg) Bracon spp., Ichneumon promissorius, Chrysoperla zatrowii sillemi, Carcelia spp., Ovomermis albicans, a nematode, Chaetopthalmus, Campoletis chloridae (larval), Lissopimpla excels, Ichneumon promissorius (pupal) etc. and predators like Coccinellids, King crow, Braconid wasp, green lacewing, dragon fly, spider, robber fly, reduviid, praying mantis, red ants etc. can be helpful for control the pest.
- Erect bird perches @ 4-8/acre to facilitate predation by insect-predatory birds.
- Install pheromone traps @ 4-5 /acre to monitor the population density of fruit borer.
Chemical control:
- Spray the crop with Quinalphos 25EC @ 640ml in 200-400 litres of water per acre.
8. White grub
White grubs, Holotrichia spp. is a polyphagous pest attacking almost all the kharif crops and rabi crops like peas and wheat.
Nature of damage
They live in soil and attack plants at all stages of growth. They mainly feed on roots of the plants which reduce the water absorption capacity of plants. The infested plant becomes pale giving wilted appearance and finally it dies.
Integrated Pest Management
Cultural
- Practice deep summer ploughing to expose the pupae to sunlight and natural enemies
- Provide adequate irrigation to crop.
- Use well decomposed organic manures.
- Practice crop rotation with sorghum and bajra.
- Trim off trees and shrubs in and around fields.
- Plant neem twigs with leaves in the field after the rain to attract and kill adult beetles.
Biological
- Install light trap @ 1 trap per hectare between 7pm to 10 pm after the receipt of first monsoon rain to attract and destroy the adult stage of the pest.
- In endemic areas, apply the fungal formulation of Beauveria brongniortii @ 2.5 kg per hectare along with FYM at the time of planting .
- Soil application of aqua formulation of entomopathogenic nematode (EPN), Steinernema carpocapsae @ 1.5 billion infective juveniles (IJs) per hectare is found effective for the management of grubs.
Chemical
- Incorporation of Chloropyriphos granules @25 kg per hectare in soil before sowing.
- Seed treatment with Chlorpyriphos 20 EC @ 6.5 - 12 ml or Imidacloprid 8 SL @2 ml per kg of seed.
- Spray Chlorpyriphos 20 EC @ 2-2.5 ml per litre of water on the nearby trees like Neem, Acacia, Subabul etc. which helps to kill the adult beetles harbouring on them.
9. Rodents
Nature of Damage:
Rats cause major damage to wheat crop and its attack starts right from sowing and continues up to the time of harvest. They eat the grains of wheat and cuts the wheat crop just above the ground level and then carry either the heads or the whole plant in to the burrows. The economic threshold level for wheat crop in case of rodents is 25 live burrows in one hectare and a damage index of 2 percent tiller damage.
Integrated Pest Management
Cultural
- Practice deep ploughing to destroy rodent burrows.
- Minimize the alternate food sources by removing the weeds and crop residues in/ around the fields
- Avoid crop rotation with rice.
- Trimming of the field bunds to destroy the existing rodent’s burrows.
- Destroy the existing rodent’s burrows by flooding or filling etc.
Mechanical
- Place tree branches or T shaped perching poles in the field to encourage predation by Owls during the night time and these bird perches should be removed just after flowering.
- Rats can be controlled by employing indigenous rat traps before the crop reaches the primordial stage.
- Disturb the habitat of the rodents by practicing burrow smoking by natural smoking materials.
Chemical
- Poison baiting with Bromadiolone 0.005 % bait (96 parts of broken rice + 2 parts of edible oil + 2 parts of 0.25% CB bromadiolone) @ 10 gm per burrow OR Zinc phosphide 2 to 2.5 % bait (96 parts of broken rice + 2 parts of edible oil + 2 parts of Zinc phosphide) @ 10g/ live burrow to be placed inside the live burrow.
- It is better to organize rodent control on a community level and baiting should be done before crop entering in to reproductive phase.
10. Stored insects pests
Insect pests of stored grains cause serious post-harvest losses of up to 9-20%. These pests feed on grains leading to loss of weight, nutritive value and germination capacity. Khapra beetle (Trogoderma granarium), lesser grain borer (Rhizopertha dominica), rice weevil (Sitophillus oryzae), grain moth (Sitotroga cerealella) and flour beetle or susri (Tribolium castaneium, T.confusum) are serious stored pests of wheat.
Webbing of grains, shot holes in grains, decay or powder and chemical excretion or silk, Foul Smell, presence of white spots on seed coat indicate the existence of eggs and dead insects and insect body fragments in a grain sample indicate the presence of stored grain pests.
Management of stored grain pest
- Ensure grain moisture of 10% at the time of storage
- The threshing floor should be cleaned and free from insect infestation.
- Harvesting and threshing machine should be cleaned before use.
- Disinfect empty godowns by fumigating with Aluminium phosphide @ 21 tablets of 3 g each for 28 cubic metres. Fumigation should be done only in air tight conditions by trained persons as the chemicals are deadly poisons.
- Maintain weed and spilled grain-free surroundings around grain storage.
- Use new and insect free gunny bags for storage.
- Never mix newly harvested grain with old grains in storage bins.
- Mix neem seed kernel, 1 kg for every 100 kg of cereals and never mix synthetic insecticides with grains meant for consumption. And also mixing of inert materials like sand, clay, ash, silica aerosols or activated charcoal with food grains is useful.
- Spinosad @ 0.1 to 1.0 mg/ Kg was effective in killing all adults and preventing population growth of lesser grain borer.
- Minimize the oxygen level less than 1 % which is lethal to pests.
- Maintain controlled or modified atmosphere (altering the proportion of oxygen and carbon dioxide) in storage chamber while storing grains which is lethal to all pests.
Authors:
Jesmi Vijayan, Prakasha T L*, Mukesh Dongre and J.B. Singh
ICAR-IARI Regional Station, Indore-452 001
*Email: