INSECTICIDAL CONTROL OF EYSARCORIS-TRIMACULATUS (DISTANT) (HETEROPTERA, PENTATOMIDAE) AND LEPTOCORISA-ACUTA (THUNBERG) (HETEROPTERA, ALYDIDAE) ON RICE IN NORTH QUEENSLAND, AUSTRALIA

The efficacy of insecticides against Eysarcoris trimaculatus (Distant) and Leptocorisa acuta (Thunberg), grain-feeding pests of rice in nort h Queensland, was assessed using a bioassay technique. Field plots of rice were sprayed, panicles collected, and the mortality of insects ca ged on them in the laboratory was recorded. Preliminary experiments id entified promising insecticides that were further assessed in replicat ed trials. Diazinon (280 g a.i. ha-1), carbofuran (1000 g a.i. ha-1) a nd dimethoate (135 g a.i. ha-1) were ineffective against both insects. Acephate (750 g a.i. ha-1) caused 100% mortality of L. acuta, but was inconsistent against E. trimaculatus. Trichlorfon (625 g a.i. ha-1) a nd carbaryl (1040 g a.i. ha-1) were inconsistent against both species. On the day of spraying, monocrotophos (300 g a.i. ha-1) killed 99% of L. acuta and 75-100% of E. trimaculatus, whereas fenthion (440 g a.i. ha-1) caused 100% mortality of both species. Endosulfan (735 g a.i. h a 1) killed > 99% of both species on the day of spraying and had some residual effect after 2 days. Chlorpyrifos at 500 g a.i. ha-1 and 750 g a.i. ha-1 killed almost 100% of both species on the day of spraying; at 250 g a.i. ha-1 it killed > 98% of L. acuta and 83% of E. trimacul atus. It had little residual effect at any application rate. Chlorpyri fos (750 g a.i. ha-1) will be recommended to control E. trimaculatus a nd L. acuta on rice in north Queensland.