Leafminer damage of “scribbles” on leaf surfaces was first reported from Washington vineyards in September of 2020. Dr. David James, Washington State University entomologist, determined the damage was caused by a new, undescribed leafmining moth, the first of its kind to damage commercial wine grapes in North America. He conducted a one-year project, supported by the Washington wine industry, to learn about distribution, abundance and potential damage to wine grape vineyards, the seasonality of the pest, and identify potential beneficial predators.
- DNA barcoding confirmed the grape leafminer is a unique species of Phyllocnistis, separate from P. vitifoliella and P. vitigenella that are found on grapes.
- Pheromone-baited traps used for citrus leafminer were deployed in 2021. This lure proved effective for the new grape leafminer, and the pest was detected in 6 of 11 AVAs that were surveyed. Aside from the Columbia Valley AVA, leafminer detections were generally very low.
- High numbers of adult leafminers in traps and damaged leaves in the Tri-Cities area suggests that this region is where the insect originated.
- Data indicates this species goes from egg to adult in 14 days, with up to 10 generations from May to September.
- It seems likely the grape leafminer will principally be a cosmetic leaf pest issue and not cause economic damage to mature vineyards. However, heavy infestations in nursery and newly-established vineyards could cause stunting and poor growth of vines.
- Although samples collected in 2021 from two leafminer-infested vineyards did not show signs of parasitoids, limited samples the previous year showed the presence of a parasitoid in the Closterocerus genus. Further work is needed to understand the importance of this species in regulating the leafminer.
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