14
Rice Brown Planthopper
to have a lot of significance in terms of perpetuation of the species. Usually migration
of BPH demands a minimum period of 3-4 days if it is a long range migration. This
ability of macropterous males to have high mating competence after 4-5 days is indeed
a boon for the insect for its perpetuation. Those macropterous males can effectively
mate with macropterous females after settling in a new favourable habitat. In case of
brachypterous males early mating vigour is the desirable trait as they have to meet
the needs of brachypterous females present in vicinity and loss of time is a loss to the
overall population growth.
Genetic control of the development of higher proportion of macropterous adults in
East- Asian Biotype compared to South-Asian Biotype of BPH has been noticed by
many rice entomologists and even reported. In East-Asian Biotype the insects are
adapted for long range migration since centuries. So development of higher proportion
of macropterous adults even when the food quality is good suggests that this trait is
already genetically fixed in BPH migrating from China to Japan and Korea. Genetic
fixing of this trait enable the BPH to start moving from Japan and Korea to China even
before actual harvest of rice crop in Japan and Korea and also from China to those two
countries during early part of the season.
Biotypes of BPH in Different Regions of Asia:
BPH populations in Asia can be grouped into three biotypes: East Asian, South-east
Asian, and South Asian (Sogawa 1992). These populations have been shown to have
different properties of 1.Insecticide susceptibility (Nagata 2002, Nagata et al 2002)
2.Wingform Response (Nagata and Masuda 1980, Iwanaga et al 1987) 3.Virulence for
feeding on resistant rice varieties (Sogawa 1992, Tanaka and Matsumura 2000). BPH
occurring in the region ranging from Northern Vietnam, China, and Korea to Japan
belongs to the East Asian population (Sogawa 1992). BPH present in The Philippines,
Thailand, Myanmar, Laos, Cambodia, Malaysia and Indonesia belong to South-
East Asian biotype. BPH present in Indian Subcontinent, including India, Pakistan,
Bangladesh and Sri Lanka can be designated as South Asian Biotype.
As early as 1977-78 when IR 26 the first BPH resistant variety released by
International Rice Research Institute (IRRI), Philippines was tested at Directorate of
Rice Research(DRR), Hyderabad, India and was found to be clearly susceptible. Later
many varieties which are resistant at IRRI showed clear susceptibility at DRR and also
