PI(s): Bergh, J Christopher (Project Leader)
Investigators: Pfeiffer, Douglas G (Investigator)
Abstract: The grape root borer (GRB), Vitacea polistiformis, is a potential threat to wine grape production in the southeastern United States. The long-term availability of the most effective pesticide for managing it and other clearwing borers, chlorpyrifos, remains uncertain due to the review of pesticide tolerances under the Food Quality Protection Act. GRB larvae are subterranean pests, feeding on the roots of vines, making their detection difficult. There are no unequivocal horticultural symptoms that can be used to diagnose GRB infestation of vines. Sex pheromones traps are effective at capturing male GRB, but since the insect also infests native vines that are often in close proximity to commercial plantings, the relationship between trap catch and infestation levels remains unknown. We are currently exploring the potential for using acoustic emissions detection technology to monitor the vibrational signals generated by the feeding activity of larval grape root borer on vine roots. This novel approach may enable more precise estimates of vineyard infestation levels and aid in developing the relationship between pheromone trap captures and larval density.
The grape root borer (GRB) is native to eastern North America, where its larvae feed on the roots of both native and commercial host plants within the family Vitaceae. While an effective sex pheromone for GRB is commercially available, there have been questions about the relationship between the capture of males in traps deployed in vineyards and larval infestation of vines. The ubiquity and abundance of its native hosts within and around eastern forests, and particularly from the Mid-Atlantic region southward, prompted a comparison of the capture of male moths in pheromone baited traps deployed in vineyard and non-vineyard habitats. This study revealed that a statistically equal number of moths were captured in apple orchards adjacent to woodlands containing wild grape and in commercial vineyards also adjacent to habitat containing native hosts. It appears therefore, that GRB is abundant in Virginia, that vineyards planted near forested areas containing wild vines are at risk from attack and that the capture of moths in pheromone traps deployed within vineyards does not necessarily reflect their emergence from within the vineyard. It is unfortunate that pheromone-based monitoring of this pest does not yield accurate information about infestation levels, given that other tactics for montioring it, for example pupal exuvia collections, are laborious and also are probably not accurate.
A technique known as acoustic emissions detection may be well-suited for addressing certain questions about the relationship between trap captures and infestation levels and about the horticultural, cultural and pest management factors that may influence vine susceptibility and larval infestation. For GRB, this method relies on instrumentation that detects, measures and digitally records the signals associated with larval feeding on the roots. Used in conjuction with GIS mapping technology, the information generated through use of this monitoring tactic may enable predictions of infestation levels and the distribution of infestations within commercial plantings as a function of soil type, vine age, proximity to native hosts or established vineyard blocks, for example.
While the acoustic emissions detection project is in the early stages of development, the results of pheromone trapping studies have yielded important information about the abundance and distribution of GRB in Virginia and about the risks posed to commercial plantings. These data have been disseminated via refereed publications and at production meetings for wine grape growers and are raising the awareness of the pest status of GRB. As stated previously, data from pheromone traps deployed in an established vineyard may not provide an accurate representation of infestation levels. However, revised recommendations will be advanced to growers this season. Since newly established blocks of vines are clean of GRB larvae, the use of pheromone traps from the outset of a new planting should provide important information about the background level of GRB populations, particularly in new vineyards not in close proximity to older, established plantings. Furthermore, accurate record keeping in combination with trapping over consecutive years may reveal increases in the moth "pressure" that reflect a building infestation in the vineyard. Conversely, accurate records of pheromone trap captures over time may reflect annual reductions of trap capture resulting from chemical and/or cultural intervention.