PROSPECTS FOR BIOPESTICIDES FOR APHID CONTROL

Diseases form an important component of the natural enemy complex of a phids. The most common and obvious of these diseases are entomophthora n fungi such as Erynia neoaphidis Remaudiere & Herbert, Entomophthora planchoniana Cornu, Zoophthora radicans (Brefeld) Batko and Conidiobol us obscurus (Hall & Dunn) Remaudiere & Keller. The pest status of some aphids such as the pea aphid, Acyrthosiphon pisum (Harris), is consid erably reduced by natural epizootics of fungal disease. However, disea se may contribute little to practical control as it is mainly effectiv e in high density populations when weather conditions are suitable. In troduction of exotic diseases for classical biological control is only rarely possible since most diseases, like their aphid hosts, are dist ributed world-wide. One exception was the successful introduction into Australia of a strain of Z. radicans for control of spotted alfalfa a phid, Therioaphis trifolii (Monell) f. maculata in 1979. Attempts to m anipulate entomophthoran fungi have had limited success because of pro blems with mass production, the fragility of the conidia and the need for suitably moist conditions. Hyphomycete fungi such as Verticillium lecanii (Zimm.) Viegas, Metarhizium anisopliae (Metsch.) Sorokin, Beau veria bassiana (Bals.) Vuill. and Paecilomyces spp. are more suitable for development as mycoinsecticides as they are cheap to mass produce and form stable conidia. ''Vertalec((TM))'', a formulation of V. lecan ii, has been sold in small quantities commercially in Britain and part s of Europe for many years and used mainly in glasshouses. Recently pr omising results have been obtained with use of M. anisopliae for contr ol of lettuce root aphid, Pemphigus bursarius (L.) in the UK. Laborato ry studies on selected isolates of B. bassiana and Paecilomyces spp. s how a promising level of activity. Problems may occur with these speci es as they can kill aphid predators such as coccinelids. In addition, more research is needed on developing improved formulations which enab le control to be achieved under low humidity conditions.