Thursday, December 30, 2010

Parasitic Winter Insects Threaten California Fruit Trees

California fruit trees are subject to a wide range of nasty winter insect infestations. While these trees may look dormant, there may actually be another world of teeming parasitic life just below the bark. Never trust appearances- it may take years before an infestation is successfully detected and by then it may be too late to salvage the tree’s health. The following threats to fruit tree health can all be successfully treated during the dormant winter months:

San Jose Scale – This particular type of scale is perhaps the most widely recognized and damaging scale insect pests found throughout California. Ornamental, shade, and fruit trees are included as part of this parasite’s list of hosts, along with more than 60 other plants. That is some serious reach. These scales are circular, convex, and grayish black and generally thrive in populations which proliferate long before symptoms are generally visible. 

Mites – Blister mites often invade pear trees, feeding on leaves and even developing fruit. The damage done can impair the functioning of leaves, but the effects are not just aesthetic. The ugly yellow “blisters” left by these pests are breeding grounds for their young. Blister mites  can only be treated during the dormant season with a thorough tree spray.

Twig Borer – Apricot, peach, nectarine, plum, and prune trees are all at risk for damage by this steel gray moth, which can grow up to half an inch long. The larvae of these borers will burrow deep down into young shoots, making it difficult to train young trees particularly. Larvae will also feed on the stems of fruits causing them to be off grade. 

Aphids – Aphids attack a wide variety of fruit and nut trees throughout the orchards of California each year. These pests can reproduce asexually, or without a mate, meaning that populations can grow uncontrollably without the proper intervention. These insects feed primarily on groups of stems and leaves. Eggs hatch in early spring but can easily be killed in the overwintering phase with a professional tree spraying during the dormant winter months.

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