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.
Sumario
El adulto Strategus aloeus (L.) (Coleoptera: Scarabaeidae: Dynastinae: Oryctini) es un insecto plaga que causa daños en plantaciones jóvenes de palma de aceite en Colombia. El uso indiscriminado de insecticidas utilizado para su control afecta a la fauna benéfica presente en el agroecosistema que regula sus poblaciones. Por lo tanto, es fundamental identificar a los enemigos nativos de S. aloeus y establecer su importancia en la regulación de las poblaciones de la plaga. Se realizaron muestreos cada 20 días durante 3 años en parcelas con estípites en proceso de descomposición de 3 plantaciones de la zona central (Colombia). El depredador Phileurus didymus (L.) (Coleoptera: Scarabaeidae: Dynastinae: Oryctini) se encontró en el 64,7% de las muestras colectadas. Las larvas, pupas y adultos de S. aloeus fueron infectados naturalmente por el hongo Metarhizium anisopliae (Metschnikoff) Sorokin (Deuteromycotina: Hyphomycetes). En condiciones de laboratorio, los adultos de P. didymus causaron la muerte de las larvas de S. aloeus después de 3 a 7 mins de encontrar su presa, tardaron entre 6 a 36 mins en consumir las larvas. El porcentaje de depredación de las larvas de S. aloeus por P. didymus estuvo en función del tiempo de exposición. A las 24 h de exposición, aproximadamente el 81,3% de la población fue depredada. Debido a su presencia dentro del agroecosistema del cultivo de palma de aceite, a los hábitos de oviposición, al factor de búsqueda y la capacidad de depredación, este enemigo natural (P. didymus) debería tener fuertes efectos en la regulación de las poblaciones de S. aloeus en el cultivo de palma de aceite.
Key Words: rhinoceros palm beetle; predation; Elaeis guineensis; Metarhizium anisopliae; Phileurus didymus
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