1. Identification, symptoms and nature of damage of Plant- and Leaf-hoppers
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2. Introduction
Rice is the world’s most important food crop and is the staple food for more than half of the population. In India, rice is grown on about an area of 45.0 million hectares with a production of 89.0 million tonnes. However, rice productivity of 3.01 t/ha in India is inferior to 6.26 t/ha in China and 3.51 t/ha in Sri Lanka.
There are over 800 insect species damaging rice in one way or other but about 20 species are of major importance and of regular occurrence. The insect pests cause huge economic loss to the rice-growing farmers in the developing world.
Yield loss due to insect pests in rice has been estimated to the tune of 21 % to 50 %. The insect pest complex of the rice crop has undergone a drastic change during the last three decades following the green revolution.
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3. Identification of Insect
Among 15 species of planthoppers and
leafhoppers known to infest rice in India, brown planthopper (BPH), Nilaparvata lugens; whitebacked planthopper (WBPH), Sogatella furcifera, and green leafhopper (GLH), Nephotettix virescens are most damaging ones.
Brown planthopper(BPH)
The BPH caused wide spread devastation of rice crop during kharif 2008 in north India and again during kharif 2010, it was serious in sporadic pockets. Yield loss could be as high as 50-90%.
White-backed planthopper (WBPH)
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4. Nature of Damage
In general, planthoppers generally remain confined to plant stems and leaf sheaths while leafhoppers occur on plant foliage. Due to this habit, planthoppers are overlooked by farmers until appearance of ‘hopperburn’ symptoms in which crop starts drying and lodging. However, during outbreaks, planthoppers can be witnessed in abundance on leaves also.
Planthoppers on rice stems
On other hand, leafhoppers feed on leaves and damage the crop. However, they are more important as vectors of virus disease “tungro”
Rice plants affected by tungro
Courtesy: agritech.tnau.ac.in
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5. Mark of identification
As the name indicates, BPH nymphs and adults are brown in colour while WBPH nymphs are white or grey and adults have a white stripe at their back.
The GLH adults are green with black spot and black patch on wings. These can be seen moving sideways on leaves.
Green Leafhopper
Courtesy: DPPQS
The BPH and WBPH occur in long-winged (macropterous) and short-winged (brachypterous) forms. These are small insects measuring mm. The BPH is also known to undertake long range migration.
Planthoppers
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6. Both nymphs and adults of planthoppers damage crop by sucking sap from plant stems and leaf sheaths, and as a result leaves start turning yellow. If not checked during initial stages, population builds up rapidly resulting in “hopperburn”. In case of BPH typical concentric circles of hopperburn can be witnessed in field. Besides direct damage, BPH also transmits grassy stunt virus disease in rice.
Crop damage (hopper burn) due to planthoppers
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7. Planthopper damaged crop
Leaf hoppers also suck sap from leaves but these are more important as transmitters of tungro virus disease than as direct feeders.
Dense rice crop under continuously flooded conditions and excess use of nitrogenous fertilizers provides very congenial environment for planthopper population build up.
Irrigation should be applied in ‘alternate wetting & drying fashion’ and if planthopper population buildup is perceived then irrigation should be withheld for few days. Likewise, excess use of nitrogenous fertilizers be avoided with emphasis on balanced fertilizer use.
Planthopper damaged crop
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8. Management practices
Proper monitoring and judicious use of fertilizers & irrigation hold key to planthopper management in rice. Monitoring can be done by inspecting plant stems at several places in all parts of field. As plant stems are tapped, these insects fall on water and can be seen swimming. Likewise, light traps can also be used for monitoring planthoppers.
Planthoppers on plant stems
Light trap
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9. Management practices Spiders
Spiders play very important role in containing planthoppers and therefore they should be conserved through selective pesticide application. This can be ensured through use of granular formulation of pesticides or leaving certain areas in the field untreated. There is also practice of placing rice straw bundles in field after transplanting to encourage spider population build up.
Economic threshold level (ETL): 8-10 hoppers/hill
Spiders
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10. Let’s sum up
Yield loss due to insect pests in rice has been estimated to the tune of 25%.
Brown planthopper (BPH), whitebacked planthopper (WBPH) and green leafhopper (GLH), Nephotettix virescens are most damaging pests of rice
Both nymphs and adults of planthoppers damage crop by sucking sap from plant stems and leaf sheaths.
On other hand, leafhoppers feed on leaves and damage the crop. However, they are more important as vectors of virus disease “tungro”.
Dense rice crop under continuously flooded conditions and excess use of nitrogenous fertilizers provides very congenial environment for planthopper population build up.
Spiders play very important role in containing planthoppers and therefore they should be conserved through selective pesticide application.
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