The following article will guide you about how to control insect pests of paddy crop.
Most of the insect pests which cause damage to crops belong to the order Lepidoptera.
1. Rice Gundhi Bug (Rice Earhead Bug):
The pest emits pungent smell.
Both nymphs and adults suck up the sap from the grains at the milky stage. Infested earheads become chaffy.
Control:
Use of light traps. Collection of and destruction of pest.
Destruction of weeds to remove alternate hosts.
Dusting of Carbaryl 5 per cent or Malathion 5% @ 25 kg./ha.
2. Rice Gall Midge/Fly:
The maggots of pest pierce at the growing point of the plant and form a gall. The affected tillers become hollow pink or purple, dirty white or pale green cylindrical tube bearing at their tips a green reduced leaf blade complete with ligules and auricles. The gall is modified leaf sheath. The damage of this pest is characteristically known as ‘Silver Shoot’ or onion shoot or Silvery galls since it produces long tubular gall of silvery appearance.
For its management spraying of 0.05% phosphomidon, 0.02% Dimethoate, 0.2% Carbaryl 0.05% Diazionon can be done at the vegetative stage of the plants at the interval of 20 to 25 days. Granular insecticides like phorate can be applied in standing water at the rate of 1 kg/ha.
3. Yellow Stem Borer:
The damage is caused by caterpillars as a result ‘Dead Heart’ formation takes place before flowering and after flowering ‘White Ear Head’ (WEH) develops. The earheads dry up and no grain formation takes place. Basmati varieties suffer heavy damage than coarse varieties.
Control:
Clipping of tips of Seedling before transplanting, Removal & destruction of stubles at first ploughing. Fields showing more than 5% ‘dead hearts’ should be sprayed with 625 ml of phosphamidon or 1.4 litres of monocrotophos or 2.5 litres of chlorpyriphos.
4. Plant Hopper:
White Backed Plant hopper (WBPH) attacks in early crop season.
Brown Plant hopper: Attacks in later crop season.
Both the hoppers suck up the sap from plant and cause a serious damage. They also emit a toxin into the plant which produces a particular symptom known as ‘Hopper Burn’.
Brown Plant hopper transmits ‘grassy stunt virus’ (GSV) to the plants.
Green leaf hopper (Jassidae) suck up the sap from leaves and transmits ‘Tungro virus’.
Insect Pest Control of Rice:
In India paddy is grown in different climatic regions. So insect pest management adopted by farmer’s changes according to cropping system and climatic regions. For various environmental regions and cropping systems different management packages have been developed which includes clean cultivation and field sanitation, wide spacing of crop plants, in timely growing of nursery and transplanting, proper crop rotation, water and fertilizer management, preventive seedling root dip, use of resistant varieties, conservation of natural enemies and judicious use of pesticides.
Weeding, destruction of weeds and alternate host plants are important components of clean cultivation.
Ploughing of fields and bunds after harvesting destroys the egg of green hoppers. The eggs are exposed to sun light and natural enemies for destruction.
Removal and destruction of stables helps in destruction of hiding insect pests.
Resistant varieties have been developed by scientists for different insect pests, e.g.
For Brown Plant Hopper –
Chaitanya, Vajram, Sonasati, Jyothi and Bharatidason –
For gall midge –
Phalguna, Suraksha, Abhaya
For Yellow stem borer –
Vikas and Sasyasree (moderate resistant)
For Rice Tungro virus –
Moderate Resistant: Vkramarya, Suraksha
Resistant variety LET 9994
Natural Enemies:
For stem borer – Testrastichus, Telenomus and Trichogramma.
For Brown Plant hopper – Dryinds, entomofagous fungi, Mirid bug.
For Leaf folder – Trichogramma, Apanteles, Brachymeria, Goniozus, Elasmus and Trichana etc.
For Gall midge – Platygaster
For control of yellow stem borer, clip the top portion of seedling before transplanting and destruction of eggs, destruction of stable, ploughing and flooding of fields, crop rotation with non- graminaceous crops, use of tolerant and resistant varieties etc. are also helpful in management of the pest.
When 50% dead heart at flowering stage and one moth or one egg mass/m2 are seen, use of Trichogramma japoncium @50,000/ha/week at the interval of one week six time is useful. If necessary safe insecticide can be used. For monitoring yellow stemborer sex pheromone is useful.
Timely transplanting, proper use of fertilizers and spacing (20 cm × 15cm) is helpful in reducing hopper population. When number of hoppers reaches at ETL (Economic Threshold Level) Mirid bugs are released and according to need pesticides can be used.
To control Rice Tungro Virus (RTV) its carrier green leaf hopper should be controlled and resistant varieties should be used.
Following insecticides are effective in paddy fields:
As Granular:
Carbofuran, phorate, Diazinon, Mephosfolon, Quinolphos. MICP and Cartap etc.
As Spray:
Chlorpyriphos, Dicrotophos, Monocrotophos and phosalone etc.
From the point of view of bio-diversity and environmental protection minimum use of insecticide is good. For this a cheap technique has been developed which as under –
Soaking of germinated seeds for 3 hours in 0.2% chlorpyriphos or Isofenphos prevents infestation of gall midge.
Dipping of seedling roots before transplanting for 12 hours in 0.02% chlorpyriphos + 1% urea for 3 hours prevents infestation of stemborer, gall midge, whorl maggots etc. for at least 25 to 30 days.
Use of carbofuran in rootzone of plants prevents infestation for long period. For prevention of gall midge and stem borer urea coated with carbofuran is used in root zone of the plant.
In rainfed upland paddy carbofuran @2 kg a.i./ha can be used in furrows to prevent pests.
In rainfed low lands mix carbofuran in soil before transplanting and spray monocrotophos or quinalphos if necessary to prevent stemborer and leaf folder.