Insect pests
1.Leaf hopper
This pest attacks the crop at its early stage of the crop. Nymphs and adults of leaf hopper are pale greenish, wedge shaped with a pair of black spots on vertex and a black spot on a posterior portion of each of the forewings and move in a peculiar fashion diagonally. Both nymphs and adult suck cell sap from the undersurface of leaves and inject toxins. The affected leaves turn yellowish and curl upwards along the margins. In case of heavy infestation, the leaves turn dark brick red ‘hopper burn’’.
2.Shoot and fruit borer
The incidence of shoot & fruit borer usually occurs during humid conditions after rain fall. The larva bores into terminal shoots of young plants leading to the death of the shoots. With the formation of the buds, flowers and fruits, the caterpillars bore inside these and feed on inner tissues. Infected buds & flowers will shed. The entrance hole is plugged with excreta. Fruits become deformed in shape with no market value.
3.White fly
Female lays stalked yellow spindle shaped eggs singly on the lower surface of the leaf. Nymphs are oval, scale like and remain attached to the leaf surface. Adults are tiny, with yellowish body and wings coated with milky white waxy powder. Nymphs and adults suck the sap usually from the under surface of the leaves and excrete honeydew. Leaves appear sickly and get coated with sooty mold. Plant shows stunted growth. It also transmits the vein mosaic virus.
4.Aphid
These are polyphagous pests. Nymphs are light yellowish black or brownish. Adults are mostly wingless but few winged forms also were seen. Cool and humid conditions are favourable for multiplication while it disappears due to good rain fall. Colonies of these nymphs and adults are often found on tender shoots and as a result of sucking of vital sap from the tissues crinkling and curling of leaves takes place. Leaves appear shiny and sticky due to honeydew excreted by the aphids. Later sooty mould grows on honeydew and leaves have a black coating.
Diseases
1.Yellow vein mosaic
There is a presence of a characteristic symptom of an interwoven network of yellow veins encompassing with islands of green tissues on leaves. Later, entire leaves turn yellow. The plants remain stunted or yellowish green in colour. Infection restricts flowering and fruits, if formed, may be smaller, yellowish and harder. This disease, spread by white fly, is an economically most important disease of okra. Sometimes the losses exceed more than 80%.
2.Powdery mildew
White floury spots or patches appear on the undersurface of the leaves which later spread to both the leaf surfaces. Initially, white superficial spots appear on leaves, but the entire surface may be covered with powdery mass. Severely affected leaves turn yellow and shrivelled. Severe infection will cause the leaves to roll upward and scorch. It may result in heavy leaf shed.
Mites
1.Red spider mite
The infestation of mites is mostly observed during the warm and dry period of the season. Larvae & nymphs are pink, greenish red while adults are oval, reddish brown. Mites feed on the under surface of leaves and as a result of feeding whitish grey patches appear on the leaves. The affected leaves gradually start curling and finally get wrinkled, mottled, crumpled, turn brown and fall.
Nematodes
1.Root knot nematode
Second stage larvae infect the plant by entering the roots. There they feed and moult to reach adult hood. They feed vigorously on roots and cause characteristic knots or galling of roots. Galls may occur singly, or several galls may coalesce to form very massive galls. Affected plants are weak, stunted with yellow leaves.
Validated Integrated Pest Management Interventions for Okra Crop
- Sow YVM resistant varieties
- Sowing of sorghum or maize all around okra field as a barrier crop for shoot & fruit borer adult moths and white flies.
- Spray NSKE @ 5 % (Azadirachtin based) 2-3 times at weekly interval for sucking pests
- Setting up of yellow sticky traps/delta traps @ 2 per acre
- Spray of propagate 57 EC or dicofol 18.5 EC @ 2ml / litre for red spider mite management
- Erection of bird perches @ 10 / acre in the field for facilitating bird predation.
- Need–based spray of imidacloprid 17.8 SL @ 100 ml or thiamethoxam 25 WG @ 100 g / ha in 500 lit water for hoppers, aphids and other sucking pests. Give another spray after two weeks.
- Removal and destruction of YVM affected plants; borer affected shoots and flower beetles time to time.
- Spray fenpropathrin 30 EC @ 250 -340 ml or oxydemeton methyl 25 EC @ 1.0 litre / ha in 1000 lit water to manage white fly.
- Installation of pheromone traps @ 2 / acre for monitoring the activity of shoot & fruit borer. Change lures after every 15-20 days.
- Spray neem oil based azadirachtin 0.03% @ 2-2.5 lit / ha in 500 lit water or spray sulphur 80 WP @ 3.13 kg / ha in 750-1000 lit water to manage powdery mildew.
- The release of egg parasitoid, Trichogramma chilonis @ 1.0 lakh/ha 4-5 times at weekly interval.
- Shoot & fruit borer infestation, if crosses ETL (5.3 %), spray emmamectin benzoate 5 WG
@ 135-170 g or chlorantraniliprole 18.5 SC @ 125 ml or quinalphos 25 EC @ 800 ml / ha in 500 lit water. - Removal and destruction of crop residues, stubbles of okra plants and deep ploughing after
harvest. Use reflective mulches of the silver, black colour of 7 μ thickness to deter white flies in early stages.
Conservation of natural enemies
The commonly seen natural enemies of pests in okra cropping system should be protected from unwanted and excessive sprays of chemical pesticides.
Source-
- ICAR- National Research Centre for Integrated Pest Management.
