Mixed deciduous hedgerows as sources of anthocorids and other predators of pear psyllid in the UK

Abstract: Anthocorid predatory bugs are the key natural enemies of pear sucker but they often migrate into orchards too late and/or in too small numbers to affect adequate natural control of pear sucker populations. A 4 year study began at East Malling Research in 2008 to develop conservation biocontrol methods to maximise anthocorid populations and other natural enemies of pear sucker in the spring. Part of this study is to identify woody species and species mixes for hedgerows/ windbreaks that act as sources of pear psyllid natural enemies, especially early in the season. Three established hedgerows with a range of plant species compositions and structures adjacent to pear orchards in Kent, UK were identified and characterised. The aim was to identify species mixes that maximise anthocorid populations in the spring and foster their migration into pear orchards when pear sucker populations start to increase. The arthropods were beat sampled from the woody species and sweep net sampled from stinging nettles at 3-4 week intervals from April to September.A large data base comprising more than 30,000 individuals, sampled and identified from 24 plant species, was constructed but not yet analysed. However, some trends in the data are obvious. 1) The largest numbers of anthocorids were found on hawthorn, goat willow and stinging nettle in the early season, while on downy birch, grey willow, stinging nettle, hazel, black alder, goat willow, field maple, blackthorn, rose and sycamore late in the growing season. 2) In the early growing season the highest numbers of anthocorids were found on the same plants that had the highest numbers of psyllids. 3) Later on, anthocorids were present mostly on plant species that had high numbers of aphids. 4) A large number of other predatory arthropods (mostly Miridae, Araneae, Dermaptera, Neuroptera, Cantharidae, Coccinellidae) also potential predators of pear psyllids were found on the hedge plants. 5) Cacopsylla pyri (L.) was discovered to be the most dominant psyllid species in the pear orchards, not Cacopsylla pyricola (Foerster), as previously reported for the UK.