Dusky-veined walnut aphid studies
IN 1928, THE EUROPEAN DUSKY-VEINED walnut aphid, Panaphis juglandis (Goeze), made its first appearance in the Western hemisphere in Oregon's Willamette Valley. The aphid first appeared on walnut trees in California near San Jose in 1952. By the following year it had spread over much of the walnut-producing area of the San Francisco Bay region. Recently the aphid has been found in Contra Costa, San Mateo, Butte, El Dorado, San Joaquin, Glenn, Sutter, Colusa, Tehama, Stanislaus, and Nevada counties.