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Increase of numbers of cereal aphids by insecticide application as an aid to plant breeding

Increase of pest populations to abnormal levels following application of pesticides is a well-known phenomenon which has been turned to advantage in work on host-plant resistance to insect pests. For example, increases in numbers of aphids followed treatment of potato with carbaryl (Sevin), DDT and other chemicals which killed aphid predators (Peterson, 1963) and carbaryl has been used where enhancement of populations of Myzus persicae was achieved deliberately (Radcliffe & Lauer, 1971; Tingey & Van de Klashorst, 1976). Interest in the possibility of breeding for resistance to cereal aphids, especially Sitobion avenae (F), has increased as more examples of differences between varieties have been reported (e.g. Kolbe, 1969; Hinz & Daebeler, 1974; Lowe, 1978, 1980; Stokes, Lee & Wratten, 1980). This aphid occurs sporadically in the field and natural enemies, notably predaceous and parasitic insects, may contribute significantly to this variation (Vickerman & Wratten, 1979), so the use of insecticides to reduce the effects of the latter appears a promising technique in the development of reliable field screening methods for plant breeding.