Spatial variation of woolly apple aphid (Eriosoma lanigerum, Hausmann) in a genetically diverse apple planting

There is an increasing requirement to breed durable resistances to woolly apple aphid (WAA) into apple cultivars. Genetically diverse apple plantings have been established in New Zealand with one aim to identify new sources of resistance to this pest, and also to allow the computation of parameters of genetic interest. Such computations are hindered by the uneven distribution of the pest in the orchard. The spatial distribution of WAA was investigated using local trend surfaces to examine large scale patterns, and point process analyses to check for the presence of small scale clumping. Large scale patterns in WAA distribution were found which could be attributed to the degree of exposure of the trees, and clumping was also detectable. The experimental design was found to adequately accommodate these spatial patterns. The application of the point process analysis to other ecological situations, and manners in which it could be extended, are discussed.