Seasonal Incidence of major insect pests of rice (Oryza sativa L. ) and its correlation with weather parameters

The present investigation was carried out to study the seasonal incidence of major insect pests of rice (Oryza sativa L.) at Agricultural Research Station (ANGRAU, Guntur), Nellore. For recording seasonal incidence of yellow stem borer, leaf folder and whorl maggot the seedlings of 27 days old were transplanted in the experimental plot (900 m2) with spacing 20 cm between rows and 15 cm between plants. A susceptible rice variety Taichung Native 1 (TN1) and a popularly grown rice variety, NLR 34449 were used as test varieties for the experiment. No plant protection measures were taken throughout the crop period to get natural pest incidence on the crop. Observations on stem borer, leaf folder, gall midge and whorl maggot infestation was recorded on 50 randomly selected hills at weekly intervals starting from 15 days after transplantation. Dead heart incidence (Stem borer) was commenced during first week of October i.e 40th standard week. Dead heart incidence was reached to its peak level (32.56 %) during 42nd standard week on TN1 and 23.3 % on NLR 34449. The leaf folder incidence was commenced from 42nd standard week both on NLR 34449 and TN1 (1.8 and 0.4 %, respectively). Then the per cent leaf folder damage was gradually increased and reached its peak during 46th standard week n NLR 34449 (21.41 %) and during 45th standard week on TN1 (17.8 %). The gall midge incidence in terms of silver shoot was initiated during 41st standard week both on NLR 34449 and TN1 (2.10 and 0.5 %, respectively). Then the per cent silver shoot incidence was gradually increased and reached its peak during 45th standard week both on NLR 34449 (15.46 %) and TN1 (18.3 %). The whorl maggot incidence was first noticed during 40th standard week on both NLR 34449 and TN1 (1.12 and 0.98 %, respectively). Then the per cent damage was gradually increased and reached its peak during 44th standard week.