Allison, D.

Cone, Wyatt W.

Pike, Keith S.

Wright, Larry C.

Undetermined

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Section IMites and Sap-Sucking InsectsABUNDANCE OF HOP APHIDS IN HARVESTED HOP YARDS,OVERWINTERING HOSTS, AND SEASONAL FLIGHTACTIVITY OF FALL MIGRANTSL. C. Wright, D. Allison, K. S. Pike, and W. W. ConeIrrigated Agriculture Research and Extension CenterRt. 2, Box 2953-AProsser, WA 99350-9687The mean number of hop aphids per leaf on the bases of hopplants that remained in fields after harvest were 4.55 in 1984,1.73 in 1987, and 5.78 in 1989. Intact plants remaining inharvested yards averaged 32.80 aphids per leaf in 1987 and 127.09in 1989.In suction trap catches from 1984 to 1990, the average datethat the first hop aphids were trapped was 1 September for femalesand 1 October for males. Collections of winged hop aphids from hopleaves in the falls of 1989 and 1990 confirmed that females flybefore males. In most years, the peak of the female flight and allof the male flight occurred after the end of harvest.Many more hop aphids were found on ornamental Prunus plantsthan on fruit trees in commercial orchards. In 1990, ornamentaltrees (72 sampled in 42 locations) had an average of 44.03 aphidsper shoot. Prune trees (149 sampled in 14 orchards) had 5.4 aphidsper shoot and most of the aphids were in one orchard that averaged80.96 aphids per shoot. No other orchard averaged more than 0.5aphids per shoot. In 1991, ornamental trees (57 sampled in 37locations) averaged 105.11 aphids per shoot; no hop aphids werefound in prune orchards (40 trees sampled in four orchards).We hypothesize that by controlling aphids on hops followingharvest, the number of female fall migrants will be reduced and thenumber of males reduced even more, leaving many females unmated.These reductions should decrease the number of eggs laid on Prunusspp., and if the reductions are large enough, the number of aphidson hops the following year should also be reduced. Controllingaphids on the overwintering hosts with a delayed-dormant sprayshould reduce the number of aphids flying to hops in the summer.We plan to apply a delay-dormant spray to ornamental Prunus in asmall hop growing area in the late winter of 1992.

Abundance of Hop Aphids in Harvested Hop Yards, Overwintering Hosts, and Seasonal Flight Activity of Fall Migrants

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Abundance of Hop Aphids in Harvested Hop Yards, Overwintering Hosts, and Seasonal Flight Activity of Fall Migrants

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