By Floconrad
United States 
My Haas avocado tree has a tree borer and there are white powdery nicks in the trunk. I scrape out the white powdery substance & spray a copper fungicide. We don't want to cut down the tree because we get wonderful fruit.
22 Aug, 2013
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Plant ID please also could I take cuttings from it? thanks »
Trees that are susceptible to tree borers are usually already weak or under stress. You need to treat the tree with with an insecticide. I can't recommend one as you are in the USA so you might not be able to get the same brands there. Go for one that contains chlorpyrifos, carbaryl, lindane or sumithion.
22 Aug, 2013