Evaluation of three Parasites in the Biological Control of Diamondback Moth in the Cameron Highlands,

The evaluation of Apanteles plutellae Kurdj and two introduced parasites, Diadegma eucerophaga Grav and Thyraeella collaris Horstn of Plutella xylostella was carried out by first measuring the searching efficiency (in terms of area of discovery (a), the killing power (K), and other biological attributes in the laboratory, and then in the field. The laboratory results indicated that D. eucerophaga was the most intrinsically superior parasite (a = 0.87, standardised followed by A. plutellae (a=0.18, and then Th. collaris (a=0.11, = 3.85). However, the field performance gave a different ranking. The mean percentage parasitism for 1977-78 was 11.7%, 8.9%, 3.0% and 0.03% respectively for A. plutellae, Th. collaris, D. eucerophaga and Tetrastichus sokolowskii, another introduced species. In 1984, a similar pattern of dominance was observed at the same sampling site, the values being 4.8%, 0.07%, 0.04% and 0% respectively. The reasons for the dominance of A. plutellae over D. eucerophaga in the field are the former parasite’s possible development of resistance to chemicals, and the high female ratio in its progeny, and the inability of D. eucerophaga to adapt to local conditions. The future of biological control of diamondback moth in Malaysia is discussed and integrated pest management incorporating mainly A. plutellae is suggested.