Insect pests management on super sweet corn at Damnoen Saduak

Predacious earwig, Proreus simulans Stallen (Dermaptera: Chelisochidae) is the most effective natural enemy of a number of insect pests at the National corn and Sorghum Research Center, Nakhon Ratchasima province. Both adults and nymphs feed on eggs and newly hatched larvae of many important insect pests of corn especially corn stem borer, Ostrinia furnacalis (Guenee) (Lepidoptera: Pyralidae); corn earworm, Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae); beet armyworm, Spodoptera exigua (Hubner) (Lepidoptera: Noctuidae). They are also predacious on corn leaf aphid, Rhopalosiphum maidis Fitch (Homoptera : Aphididae) as well. The objective of this research was to determine the suitable control measure of the important insect pests of super sweet corn and the best financial return at Damnoen Saduak, Ratchaburi province during October 1995-April 1997. There were four methods: 1) Untreated plot ;2) Treated plot (farmer's practice); 3) Biological control (releasing P. simulans); 4) Biological control (3)+spraying recommended insecticides at the economic threshold level (ETL) for the control of corn stem borer, corn earworm, beet armyworm and corn leaf aphid (IPC). It was found that the population of corn insects in untreated plot was lower than the ETL except the infestation of the corn leaf aphid at 50 days after emergence (DAE). In the condition, the IPC and biological control plots were released by 1 earwig per plant at 10 and 20 DAE in 1996 and 0.25 earwig per plant at 10 DAE in 1997. The IPC was also sprayed with 0.04 percent lambda cyhalothrin (Karate 2.5 percent EC) at 52 DAE for the control of corn leaf aphid while the farmer's practice plot was sprayed 6 and 4 times for the control of insect pests throughout the crop season in 1996 and 1997. The results of two-year experiments revealed that the IPC method gave the highest marketable ears (70.33-82.06 percent) and the best financial return (1,306.08-3,098.73 baht/rai). The cost benefit ratio ranged 1:7.10-1:16.68 and a number of applications was reduced 75.00-83.33 percent compared with the farmer's method.