Life Cycle and Natural Enemies of Demotispa neivai (Coleoptera: Chrysomelidae)

摘要

Demotispa neivai (Bondar) (Coleoptera: Chrysomelidae) causes significant palm oil loss due to the damage it causes to the epidermis when feeding on fruit of oil palm, Elaeis guineensis Jacq. This research was conducted to characterize the biology and natural enemies of D. neivai. The life cycle was studied under laboratory conditions (28.8 degrees C +/- 1.2 degrees C and 76.8% +/- 6.3% relative humidity); population fluctuation was established in field conditions using a 5-yr-old oil palm plot. Natural mortality factors of D. neivai were recorded over a 22-week period, with sampling of bunches occurring once every 2 weeks over five phenological stages of fruit development. At each sampling, three bunches were selected per stage. The D. neivai life cycle was as follows: the egg stage was 7.1 +/- 1.2 d, the larval stage with five instars was 21.9 +/- 2.0 d, the pupal stage was 19.6 +/- 3.0 d, and the adult stage lasted 268.9 +/- 53.1 d. The entire life cycle was, thus, completed in 309.1 +/- 54.3 d. The largest D. neivai populations were recorded in oil palm during the bunch-filling phenological stage. Their most important natural mortality factor was the fungus Metarhizium anisopliae (Sorokin) Metchnikoff, which caused, on average, 25.3% larval mortality.