The effect of infestation with rice water weevil (Helodytes foveolatus Duval) on the growth and development of rice (Oryza sativa L.) in Guyana

Rice (Oryza sativa L.) production, the largest agricultural sub-sector in Guyana, is greatly affected by insect pests. The rice water weevil (Helodytes foveolatus Duval) is an early-season pest of rice at both the adult and larval stages with the latter resulting in the greater yield loss. This study compared the growth and development of rice plants subjected to varying levels of water weevil larvae infestation. Plants were infested with 3, 5, and 7 larvae/plant at two periods: 18 and 30 days after sowing (DAS). Uninfested plants served as the control. Each treatment was replicated five times and plant height, tiller count, panicle emergence and panicle density were recorded. Results showed that there were significant differences in plant height at maturity and throughout the trial, for infestation treatments applied at 18 and 30 DAS. At maturity, a similar trend was observed in the number of tillers produced by the various treatments; plants infested at 18 and 30 DAS with 7 larvae/plant had significantly lower number of tillers than the control and plants infested with 3 and 5 larvae/plant (P=0.03 and P=0.02) respectively. Panicle emergence and panicle density were also influenced by the number of water weevil larvae per plant and the length of time of infestation. This study proves that growth and development of rice plants can be affected by the level of infestation and the time of infestation of rice water weevil larvae. This can be useful in determining the amount of damage caused by the pest and therefore indicate to farmers whether or not control measures should be applied.