Abstract. Herlinda S, Alesia M, Susilawati, Irsan C, Hasbi, Suparman, Anggraini E, Arsi. 2020. Impact of mycoinsecticides and abamectin applications on species diversity and abundance of aquatic insects in rice fields of freshwater swamps of South Sumatra, Indonesia. Biodiversitas 21: 3076-3083. Aquatic insects in rice fields generally are predators of rice insect pests. The application of insecticides may reduce the abundance and species diversity of these predators. This study aimed to determine the impact of mycoinsecticides and abamectin application on species diversity and abundance of aquatic insects in rice fields. Mycoinsecticides were made from Beauveria bassiana s.l., Metarhizium anisopliae s.l. and Cordyceps militaris s.l. with carrier from shrimp shell flour compost extract, vegetable oil, and Tween®. The treatments were the mycoinsecticides and abamectin. The results showed there were eight aquatic insects species obtained in this study, i.e. unidentified Dytiscidae, Micronecta sp., Mesovelia sp., Ranatra sp., Anisops sp., Microvelia sp., unidentified species of Veliidae, and Orthetrum sp. belong to 7 families (Dytiscidae, Corixidae, Mesoveliidae, Nepidae, Notonectidae, Veliidae, Libellulidae), and three orders (Coleoptera, Hemiptera, and Odonata). All of the species were predatory insects. The application of mycoinsecticides did not reduce the abundance and species diversity of the aquatic predatory insects, but the application of abamectin reduced the abundance and species diversity of the predators. The highest insect species diversity was in the plots applied with C. militaris s.l., followed by the B. bassiana s.l. and M. anisopliae s.l. plots and the lowest one was found in the abamectin plot. So, the application of mycoinsecticides from B. bassiana s.l., M. anisopliae s.l. and C. militaris s.l. is safe for the aquatic predatory insects and to control rice insect pests than that of abamectin.

Basal stem rot of oil palm caused by Ganoderma boninense is difficult to be controlled due to abundance of inoculum sources in the field. This study was aimed to determined effects of taro plants viz. Belitung taro (Xanthosoma sagittifolium), Bogor taro (Colocasia esculenta), and Japanese taro (Colocasia esculenta var. antiquorum) on decay of G. boninense inocula. Pathogen inocula as rubber wood block (RWB) colonized by G. boninense was attached with main roots of oil palm seedling and buried into soil of oil palm seedling (monoculture), mixed planting of oil palm and taro plants, or of taro plants monoculture. Burying of pathogen inocula for 3 and 6 months on taro plant resulted in 2.1 times higher decay of RWB compared than oil palm monoculture. Increasing of decay also exhibited on mixed cropping system, but it was slightly lower than on oil palm monoculture. This result suggesting the benefit of taro plants either planted under monoculture or mixed cropping to fasten decomposition of infected wood debris as an inoculum source of G. boninense.