IMPACT OF LEAF EATING CATERPILLAR CONTROLS ON THE DIVERSITY OF INSECTS IN ASIATIC PENNYWORT FARMS

Abstract

Annual loss of Asiatic pennywort production is primarily due to lepidopterous larvae.The pennywort cutworm (Zonoplusia ochreata) is one of the most destructive leaf feeders of pennywort.Most Thai growers prefer chemical controls to prevent production loss.Bioinsecticide is an alternative to synthetic insecticides.Some organic growers used Bacillus thuringiensis and neem extract for lepidopterous control in pennywort farms.We should understand how diversity of target and non-targeted species in the areas is impacted by different control management.Therefore, four preventative treatments were trialed: natural control in organic farming, Bacillus thuringiensis, neem extract and abamectin, to evaluate their effect on the biodiversity of insects in Chainat, Nonthaburi and Bangkok provinces, all located in the central region of Thailand.After 8 weekly spray applications, the insects were collected using the sweep sampling method.A total of 561 insects were identified belonging to 38 different species, including 34 predator species, and 29 parasitoid species.The effect of different treatments on the species diversity index and evenness index was calculated.Shannon's species diversity index (H') was higher in the natural control area (2.74) compared to areas treated with Bt (2.09), neem extract (1.90) and abamectin pesticide (1.88).The evenness index showed a similar trend; natural control (0.82), Bt (0.57), neem extract (0.62) and abamectin (0.55).The results support the hypotheses that organic farming promote insect diversity.Environmentally insect control approaches enhance biodiversity and ecological service in farmland.