Changing Scenario of Rice Gallmidge Biotypes at Warangal and Computation of their Growth Rates

Seventeen donors and twelve differentials were screened separately against rice gall midge, Orseolia oryzae (Wood-Mason) in two field experiments conducted during Kharif 1999-2001 at Agricultural Research Station, Warangal, to monitor their reaction. Based on their reactions, evolution of new biotypes and their population growth rates were studied. Among the 17 donors, Phalguna and RP 2068-18-3-5 recorded resistant reaction during 1999 only while all the donors recorded susceptible reaction during 1999 and 2000. Similarly, the reaction of 12 differentials, in four groups, during 1999-2001 recorded a progressive change in their reaction against virulent rice gallmidge. The growth rates of virulent populations were calculated as 0.49, 0.59 and 0.74 during 1999, 2000 and 2001, respectively. To overcome the evolution of new biotypes certain management aspects were discussed.