THE BENEFICIAL FAUNA OF STRAWBERRY FIELDS IN SOUTH-EAST ENGLAND

Surveys were made of fields of strawberries of various cultivars and f lowering/fruiting seasons in south-east England to determine the compo sition and relative abundance of the beneficial arthropod fauna. Most fields had a minimal spray programme, with nil or one insecticide trea tment per season. Spiders were consistently the most abundant group of polyphagous predators in suction or tap samples. Anthocorids, mainly Orius spp., sometimes became numerous, particularly on everbearer cult ivars. Numbers of coccinellids, chrysopids and predatory mirids were u sually very small. Hymenopteran parasitoids were often numerous in fie lds with large aphid populations. Two species of phytoseiid mites and the larvae of a cecidomyiid midge were found in leaf samples, in assoc iation with colonies of twospotted spider mite. Aphid numbers reached damaging levels in some fields, despite the presence of large numbers of predators. Spider mites also reached high numbers in some fields, b ut populations declined where predatory phytoseiids colonized the plan ts. Large variability in numbers of beneficial arthropods occurred bet ween fields over short distances.