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Aphids All Around in Spring 2011

  The long warm fall of 2010 in northern Utah gave aphids plenty of time to mate and lay hundreds of eggs on a wide variety of hosts, making for aphid problems this spring.

Aphid populations have been higher this spring than many can remember in years. On fruit trees we’ve seen black cherry aphid, green peach aphid, mealy plum aphid, leafcurl plum aphid, and apple aphids. On landscape plants: rose aphid, spirea aphid on a number of species, honeysuckle aphid, sunflower aphid on dogwood, linden aphid, elm leaf aphid, Norway maple aphid, giant conifer aphid, and many more. Not only were they abundant, but on a few host plants, egg hatch occurred very early; even before bud break. A variety of factors combined to make the “perfect storm” for the aphid eruptions.

One of the biggest factors was what happened last fall. Low-level jet winds in September blew aphids north from southern Utah and Arizona, and the long-lived Southwest Monsoon kept nighttime temperatures in the 40s through to mid November, resulting in large swarms of aphids that had plenty of time to multiply, mate, and lay eggs on overwintering hosts. The weather this spring then helped to magnify an already large starting population. Aphids are a cool-season pest, and thrive on the healthy, succulent plant tissue that has been plentiful this spring.

The good news is that many of these aphid species migrate to alternate hosts for the summer, and will be leaving the plants they are now on very soon.

Also, the abundance of prey leads to a subsequent abundance of predators, some of which were active very early this spring, including wasp parasites and larvae of syrphid flies and lady beetles.

-Marion Murray, IPM Project Leader