OVERWINTERING IN 6 ARABLE APHID PESTS - A REVIEW WITH PARTICULAR RELEVANCE TO PEST-MANAGEMENT

The over-wintering strategies of 6 aphid pests of arable crops are discussed. Three, Sitobion avenae, Rhopalosiphum padi and Metopolophium dirhodum are important pests of cereals world-wide. The other three, Aphis fabae, Acyrthosiphon pisum and Myzus persicae are serious pests of Vicia, Pisum and Solanum species respectively. All 6 aphids show a variety of overwintering strategies. A. fabae, M. dirhodum and R. padi are mainly host-alternating (heteroecious) holocyclic species; A. pisum and S. avenae are single host (autoecious) holocyclic species. Myzus persicae is mainly anholocyclic and autoecious although it can be holocyclic and heteroecious. The degree to which each aphid specialises in a particular mode of overwintering is discussed. The amount of mortality likely to be experienced by eggs (70%) and viviparae (up to 100%) is compared and contrasted. Natural enemies are the major factor causing egg mortality and low temperatures are the greatest single cause of mortality affecting the viviparae. Systems predicting aphid numbers on summer crops, based on winter populations of aphids are described and assessed as to their accuracy.