Factors influencing the temporal and spatial patterns of dogwood borer (Lepidoptera: Sesiidae) infestations in newly planted apple orchards

Abstract

The temporal and small-scale spatial patterns of infestation by larval dogwood borer, Synanthedon scitula (Harris) were studied from 2002 to 2004 in two newly planted apple orchards in West Virginia and Virginia. Rootstock, tree variety, and cultural management practice were significantly associated with the presence and extent of dogwood borer infestation. In West Virginia, infestation was significantly greater on trees planted on M.26 rootstock compared with M.7 rootstock, and on trees fitted with tree guards compared with other trunk treatments. In Virginia, the proportion of infested trees was significantly greater for 'Idared' tree varieties compared with 'Buckeye Gala', and on trees fitted with tree guards compared with other trunk treatments. Median polishing technique was used to separate variability in the infestation data into large-scale variation (trend) induced mainly by treatments and small-scale variation. Variography was used to study the median-polished residuals of infestation that represent the small-scale variation. The results of variogram analysis of the median-polished residuals indicated that there were moderate to high degrees of aggregation in dogwood borer infestations on neighboring apple trees (Malus domestica Borkh.) with ranges of spatial autocorrelation from 2.8 to 17.0 m. The spatial patterns of the aggregation of infestation in the West Virginia and Virginia orchards were best described by the spherical and exponential semiovariogram models, respectively. Interpolated surface maps of the median-polished residuals revealed local hot spots, which were generally more prevalent within tree guard treatments, and were typically found where dogwood borer infestations originated. Results are discussed in relation to the sampling and management of dogwood borer larvae. © 2011 Entomological Society of America.