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Rice Brown Planthopper
High titre of JH is induced in an individual BPH due to exposure to optimum
food or environmental conditions in the first instar and is responsible for
destining the insect to brachypterous adult.
Maintaining high titre of JH requires a mechanism for synthesis and degradation.
These are facilitated by up-regulation of concerned genes involved with
synthesis of required enzymes.
Induction of high JH in the first instar to regulate morphoform development
appear to have deeper significance for BPH survival as a species. During kharif
season optimum environmental conditions and food quality are maintained
throughout and enable the insect for rapid multiplication and more damage.
When initial senescence starts, the first instar nymphs emerging at that crop
stage invariably taste the poor quality plant sap. It acts as a signal to produce
low JH and fixes almost all of them to become macropterous adults. Thus BPH
migration starts much earlier than full crop maturity. While during rabi high
temperatures setting in much earlier than senescence of crop appear to induce
macroptery and consequently the migration starts even when the food quality
still remains favourable. This type of signaling mechanism enables BPH to
completely avoid the forthcoming adverse conditions.
Crowding or nymphal density is not responsible for higher macroptery.
High mating potential in macropterous males at 4-5 days after emergence
facilitates mating after migration process is over while in brachypterous males
high mating potential immediately after emergence suits for higher population
build up under already existing favourable conditions.
There are three biotypes of BPH in Asia viz., East Asian, South-east Asian, and
South Asian. Insecticide susceptibility, Wing-form Response and Virulence for
feeding on resistant rice varieties formed the basis for grouping. BPH occurring
in the region ranging from Northern Vietnam, China, and Korea to Japan
belongs to the East Asian population. BPH present in Philippines, Thailand,
Myanmar, Laos, Cambodia, Malaysia and Indonesia belong to South-East
Asian biotype. BPH present in Indian Subcontinent, including India, Pakistan,
