Control of the live-wood tea termite Glyptotermes dilatatus using Heterorhabditis Sp. (Nemat.)

Abstract

Glyptotermes dilatatus is the main pest of the lowland-grown tea in Sri Lanka, affecting some 42 000 ha. Infested bushes suffer debilitation of their structure, loss of yield and death. The concealed habit of Glyptotermes and its social organization makes it difficult to control by chemical, classical biological and other conventional methods. It was recently found that the nematode Heterorhabditis sp. (isolated in Darwin, Australia, and mass-produced by CSIRO entomologists) infests Glyptotermes and is able to kill the termite and breed in the cadaver both in the laboratory (22°C; 100% relative humidity) and under extreme climatic conditions experienced in the field (mean temp.: 28.3°C; range, 19.5–38.4°C; only 7 days low rainfall between 20 December 1981 and 28 February 1982). Within each cadaver, up to about 3500 juveniles were produced which are able to infect healthy termites in the laboratory as well as in the field, creating a chain of infection that leads to complete annihilation of a colony. In the laboratory, the dosage mortality equation predicted an LD 50 of 3670±564 worms/ml, suggesting that a very high rate of application is needed to obtain 99.9% kill. In the field, experimental application of infectives at rates of 4000 and 8000 worms/ml in doses of 40 and 30 ml per bush, respectively, gave complete control within 60–95 days. The cost of control is US$2.39 (50.20 Sri Lankan rupees) per 1000 infected bushes (1987 values).