Evaluation of the biological control program against Diatraea spp. (Lepidoptera: Pyralidae) on sugar cane in Trinidad.
Inoculative releases of the imported tachinids Lixophaga diatraeae and Metagonistylum minense were conducted in sugarcane plantations in Trinidad over a period of 15 years for the control of Diatraea spp. (mainly D. saccharalis). However, permanent establishment of the parasitoids has not been recorded. The most effective tachinid has been the indigenous species Paratheresia claripalpis, with a specific parasitism rate of 5.0%, followed by L. diatraeae (0.6%) and M. minense (0.2%). Other parasitoids include Cotesia flavipes (5.0-10.0% parasitism) and Agathis stigmaterus [Alabargus stigma] (0.5-2.0%). Allorhogas pyralophagus, introduced from Mexico, had a parasitism rate of <5.0%. Following the release of 11 parasitoid species, the overall parasitism rate was 16.3-23.5%. This resulted in a gradual reduction of damage due to Diatraea spp. from 16.9% in 1984 to 5.7% in 1987. Computer predictions indicated a reduction in damage by Diatraea spp. to below the accepted economic threshold of 5.0% during 1987-89.