Native Enemies of Strategus aloeus (Coleoptera: Scarabaeidae) in Oil Palm Plantations in Colombia

Abstract

The adult Strategus aloeus (L.) (Coleoptera: Scarabaeidae: Dynastinae: Oryctini) is a pest insect that causes damage in young oil palm plantations in Colombia. The indiscriminate use of insecticides for their control affects the beneficial fauna of the agroecosystem, reducing their populations. Therefore, it is essential to identify S. aloeus native enemies and establish their importance in regulating pest populations. Sampling was performed every 20 d for 3 yrs in plots with decomposing stipes in 3 plantations of the central zone (Colombia). The predator Phileurus didymus (L.) (Coleoptera: Scarabaeidae: Dynastinae: Oryctini) was found in 64.7% of the collected samples. Strategus aloeus larvae, pupae, and adults also were naturally infected by the fungus Metarhizium anisopliae (Metschnikoff) Sorokin (Deuteromycotina: Hyphomycetes). Under laboratory conditions, adults of P. didymus caused the death of S. aloeus larvae 3 to 7 mins after finding their prey, taking 6 to 36 mins to consume the larvae. The percentage predation of S. aloeus larvae by P. didymus was a function of exposure time. At 24 h of exposure, approximately 81.3% of the population was predated. Due to the presence within the agroecosystem of the oil palm, the habits of oviposition, the search factor, and the predation capacity, this natural enemy (P. didymus) should have strong effects on the regulation of the populations of S. aloeus in oil palm cultivation.