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Biological Improvement of Chestnut Through Technologies That Address Management of the Species, Its Pathogens and Pests
Department of Entomology
The overall impact of this project will be to further the progress being made toward the restoration of chestnut as a tree in North American forests and as a nut in the American marketplace.
2009 Project Description
Asian chestnut gall wasp galls are being collected from the leading edge of the infestation in eastern North America to evaluate natural enemy composition and recruitment. Galls are measured and dissected, morphological characteristics of inhabitants are recorded, specimens are extracted and stored for subsequent molecular analysis (pending). A Korean and a Japanese strain of Torymus sinensis, the primary biocontrol agent for the Asian chestnut gall wasp, are present in Asia, distinguishable through phenological differences in development. The strain released in the USA is unknown. Asian chestnut gall wasp collections are ongoing to monitor Torymus sinensis emergence, to evaluate which strain is present in the US. Collaborators in Pennsylvania, Ohio, and Maryland are contributing material.
We are evaluating selected plant signaling compounds for their potential roles in Asian chestnut gall wasp gall development, including fitness and defense. Selected compounds and associated inhibitors are applied exogenously to developing galls, including ethylene and its inhibitor (STS), and abscissic acid and its NDGA inhibitor. Gall weight, volume, and the number of fungal lesions are evaluated. The number of chambers, mortality, parasitism, and fungal infection are assessed. Attempts to artificially infest chestnut seedlings with the Asian chestnut gall wasp continue. American chestnut seed germinated and seedling development monitored. Attempts to infest seedlings with ACGW failed (similar to previous attempts by R. Cooper with F1 hybrids). Current focus is to manipulate European chestnut and attempt to artificially infest.
These project descriptions were disseminated to the scientific community via several presentations, including an invited seminar at the Virginia Tech Department of Entomology, and submitted presentations at the Entomological Society of America National Meeting in Indianapolis, IN, and the Southern Forest Insect Work Conference in Gulfport, MS. Lastly, a research summary was presented at the NE-1015 Regional meeting in Ocean Grove, NJ.
The numerically dominant parasitoid of the Asian chestnut gall wasp is Torymus sinensis, a hymenopteran introduced for gall wasp control in the mid 1970's. It is spreading with expanding gall wasp populations, and affords moderate population control.
Ormyrus labotus is a native hymenopteran that is the second most abundant parasitoid associate of the gall wasp. It is an associate of oak-galling cynipids, and appears to have expanded its host range to take advantage of the novel resource provided by the presence of the introduced Asian chestnut gall wasp.
Ethylene and its inhibitor affected several parameters on both American and F1 hybrids. Gallmaker fitness, as measured by gall weight and gall volume, was reduced by ethylene applications, as was the galls' source strength (number of leaves). The ethylene inhibitor compromised gallmaker defense, measured by the number of fungal lesions forming on the gall exterior. Exogenous applications of abscisic acid reduced the defense response of American chestnut, but weakly increased the defense response of the F1 hybrids. Abscisic acid and its inhibitor had other more moderate effects that were measurable only on the F1s, including effects on gallmaker fitness and source strength.
Cooper, W.R. and L.K. Rieske. 2009. Woody stem galls interact with foliage to affect community associations. Environmental Entomology 38, 417-424.
Cooper, W. R. and L.K. Rieske-Kinney. 2009. Sustainable Management of the Invasive Asian Chestnut Gall Wasp Interactions between native and introduced natural enemies. Nutshell, June.