Grape root borer

Abstract

Over a century ago, a statement by the observant entomologist F. E. Brooks from West Virginia, the US, captured one of the fundamental issues underlying the infestation of vineyards in the eastern US by larvae of the grape borer, Vitacea polistiformis (Harris): 'So inconspicuous is the insect itself, and its manner of working, that a vineyard may be suffering greatly from its attacks and yet those who have the care of the vines remain entirely ignorant of the cause of the trouble' (Brooks 1907). Seven decades later, Dutcher and All (1979a) reiterated this ongoing problem, stating that 'Due to the cryptic nature of the grape root borer larva and the chronic, yet pernicious impact of larval feeding on vine vigor, infestations are often not noticed until severe damage has occurred'. Despite long-standing recognition of the potential threat from grape root borer (reviewed in Brooks 1907) and a considerable body of published research and observations on aspects of its biology, behavior and management, the deleterious effects from this troublesome pest continue to plague many eastern US vineyards. This is likely due to a combination of factors, not least of which is the insidious nature of the development of a grape root borer infestation. Detection of, and early intervention against, infestations requires experience and education that many growers or crop consultants do not possess and a continuing level of diligence that many have not applied. Furthermore, the expansion of the eastern US wine grape industry since the 1970s has focused primarily on European grape (Vitis vinifera L.) varieties and their hybrids, many of which are grafted to rootstocks developed from crosses of American grape species considered susceptible to grape root borer. Such factors would be expected to increase the incidence and severity of problems from the pest, especially as vineyards age. Perhaps most importantly however, the development and delivery of monitoring and management tactics for grape root borer based on modern IPM principles have not kept pace with those now considered routine for controlling many other lepidopteran pests of agricultural crops. A truly integrated strategy for managing grape root borer is not presently available. This, I believe, is due to some fundamental knowledge gaps concerning the ecology and behavior of the grape root borer that have impeded the development of best management practices.