Section VI. Soil

SURVEY FOR CALIFORNICUS IN OREGON HOPS James G. Todd Willamette Agricultural Consulting, Inc 7555 St, NE Salem, OR 97301 503/378-7003

Larva of Pri onus cali fornicus Mots, feed on the roots of living deciduous trees and since the 1930's they have also been observed damaging the roots and crowns of hops in southwest Idaho. Larvae spend up to four years completing their feeding cycle deep within hop roots and then adults emerge for a brief period in July to mate, disperse and lay eggs. Larval feeding in hop roots may cause vines to wither and die in mid-summer and heavily infested crowns can be completely destroyed. In cases of severe injury it has been necessary to remove infested hop yards. There is no effective chemical treatment for this pest in established hops.

This pest has recently been reported in hops from the Yakima Valley, WA, and efforts Are being made to assess the impact of this on Washington's hop industry. A single of Pri onus was found in hops near Independence, OR, in August, 1995, by Willamette Agricultural Consulting. This survey was initiated by the Oregon Hop Commission to determine the distribution and density of Pri onus cali fornicus in Oregon's hop growing areas. A standard U- tube Blacklight trap

No Pri onus cal i f ornicus adults were collected in* Blacklight traps monitored from mid-June through mid-Sept. No P. californicus larva were found in 80 hop crowns dug from four hop yards. One larva was found in a hop crown near Monitor, OR, and six adults were collected in or near hop yards from late-July to early-Sept., 1996. Prionus californicus is present in Oregon hops, but densities appear to be low. We saw no evidence of economic damage by this insect.

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