Oviposition by the riceinfesting weevil, Oryzophagus oryzae (Costa Lima, 1936) (Coleoptera, Curculionidae): influence of water depth and host-plant characteristics

R.P. Moreira, Gilson

Following characterization of the egg-laying site, oviposition site selection by the rice-infesting weevil Oryzophagus oryzae (Costa Lima, 1936) (Coleoptera, Curculionidae) was studied in relation to water depth, age and density of rice in outdoor tanks. Experimental units consisted of plastic pots that were filled with different soil amounts to obtain the desired water depths in the tanks. Most eggs were laid in the submerged portions of the leaf sheath within the leaves internal air space (aerenchyma). Oviposition rates increased linearly from 10.9 to 54.5 eggs per plant with an increase in water depth from 0 to 12 cm. There was a significant interaction between water depth and host plant age, and tiller density. In water varying from 4 to 12 cm deep, females oviposited significantly more eggs on 60-day old plants (average > 75 eggs per plant) than on 15-day old plants (average 30 eggs per plant). Oviposition was negligible on 105 and 150-day old plants. Oviposition rates increased with tiller density in the 4-12 cm water depth interval. The dataindicate that females oviposit preferentially on tillering rice plants in relatively deep water, and that egg density is directly related to the number of tillers per plant.