- Author: Kathy Keatley Garvey
Hishinuma, who is seeking her doctorate, studies the walnut twig beetle, Pityophthorus juglandis, which in association with a newly described fungus, Geosmithia morbida, causes thousand cankers disease (TCD) of walnut and butternut trees.
Hishinuma works with major professor Mary Louise Flint and is co-advised by chemical ecologist and forest entomologist Steve Seybold of the Pacific Southwest Research Station, USDA Forest Service, Davis, an affiliate of the department. Flint serves as an Extension specialist with the UC Davis Department of Entomology and Nematology and as the associate director for urban and community IPM, UC Integrated Pest Management Program. Both Flint and Seybold plan to attend the conference.
Previous recipients of the annual award have gone on to develop professional careers in forest entomology in academia or with the USDA Forest Service. UC Davis postdoctoral researcher Andrew Graves of Plant Pathology won the award in 2005 while a student at the University of Minnesota.
WFIWC is the core organization for forest entomologists in western North America with membership not only in the United States, but also in Canada and Mexico. The organization was founded in 1949 to provide an informal opportunity for forest entomologists to exchange new ideas and findings prior to each upcoming field season. It established the Memorial Scholarship Fund in 1990 to memorialize member Mark McGregor of the USDA Forest Service and later PheroTech Inc., who died in Idaho while working on research. Other contributions have since honored additional colleagues.
Hishinuma also received two scholarships from the California Garden Clubs, Inc. (CGCI) and a McBeth Memorial Scholarship to support her research on TCD.
The walnut twig beetle is believed to be native to Arizona, California, New Mexico and Mexico. In 2006, plant pathologist Ned Tisserat and entomologist Whitney Cranshaw of Colorado State University identified the pathogen in declining black walnut trees in central Colorado. The disease has now spread east of the Mississippi to at least five states in the heart of the valuable black walnut timberlands. Latest statistics show that the beetle and pathogen are now known from nine states in the western U.S. and four states in the eastern U.S. There is a fifth state (Maryland) where only the beetle has been found and a sixth state (North Carolina) where only the pathogen has been found.
Seybold's research group has led the effort to characterize the disease in California and to develop a nationwide detection program for the beetle. Scientists believe that TCD occurs only on walnut, butternut, and wingnut, but it is most damaging to native black walnuts, Juglans californica, J. hindsii, and J. nigra although the disease has been recorded on at least 10 species of walnuts or their hybrids in California. Often the first symptoms of TCD are flagging and yellowing leaves and branch dieback, Seybold said. Affected branches show sap staining and pinhole-sized beetle holes. Beneath the surface are dark stains caused by the fungus.