Toxic baiting of the Western yellowjacket (Hymenoptera: Vespidae) in Hawaii.

Abstract

Forager populations of the western yellow jacket, Vespula pensylvanica (Saussure), regularly declined in Hawaii in December despite the warm winter. This decline may be correlated with the significant shortening of daylight and the decrease of solar radiation in August and September. Toxic baiting should be initiated when daily catch of foragers reaches 50 yellowjackets per trap. Intensive baiting in an infested area with 0.5% microencapsulated diazinon (Knox-Out 2 FM) mixed with canned Figaro brand tuna cat food at a dispenser density of 0.2/ha was effective in controlling yellowjackets. Low dispenser density (e.g., one dispenser per 20 ha) and baiting early in the season depressed the forager population only when the baiting program lasted until October. Yellowjackets preferred tuna over meat or liver in a bait-preference test. Baits with 100 ppm avermectin B1 and 1% fenoxycarb required 7 wk to be effective, whereas amidinohydrazone was effective within 1 mo. In a color-preference test, translucent (white) wet traps captured more yellowjackets than other colors. However, yellowjackets took similar amounts of bait from bait dispensers regardless of dispenser color.