Review: Natural enemies and biocontrol of pests of strawberry in northern and central Europe

The natural enemies of the more important arthropod, nematode and mollusc p ests of strawberry in northern and central Europe and their use as biocontr ol agents are reviewed. Most pests of strawberry are polyphagous and they a nd their natural enemies occur on other host plants (especially Rosaceae) a s well as on other crops. Strawberry cultivation methods, including protect ed cultivation and other methods of extending the fruiting season, soil ste rilization, polythene mulching and pesticide spray programmes have profound influences on the pest and natural enemy complex, though such effects have not been quantified adequately. All the pests of strawberry reviewed have natural enemies, though some pests (e.g. capsid bugs) have few. A few natur al enemy groups are known to act as important natural limiting factors in p est population development in commercial strawberry crops. Two examples are naturally-occurring phytoseiid predatory mites which regulate pest mite po pulations, and predatory carabid beetles which regulate root weevil populat ions. Apart from the introduction of predatory phytoseiid mites to control two-spotted spider mite, biocontrol is not widely used in commercial practi ce. Other biocontrol approaches are known to be efficacious, but are too co stly in comparison with conventional insecticides for commercial adoption ( e.g. nematodes for slug control). Several biocontrol approaches have been r esearched and have potential for further development and exploitation and t here is considerable opportunity to develop new approaches. Research effort should concentrate on those for common pests, which are controlled current ly by frequent sprays of broad-spectrum insecticides, e.g. aphids, blossom weevil, capsids and vine weevil. As strawberry is often grown as an annual or short-term perennial crop, exploiting natural populations of natural ene mies is difficult. More effort needs to be devoted to the development of mi crobial and nematode biocontrol agents, which can be used as biopesticides. Protected cultivation of strawberry provides more favourable conditions fo r exploitation of biocontrol including introduction of insect predators and parasites.