Good Fruit Grower

December 2015

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66 DECEMBER 2015 Good Fruit Grower E ntomologists are trying to help fruit growers as they face another trunk-boring insect, the black stem borer. It's been killing trees, enough to cause worry that a bigger outbreak may be coming. Right now, controlling it is diffi cult, so the interim advice is, watch out for it and remove infested trees from the orchard and burn them. "We don't know how to control it yet," said Cornell University entomologist Art Agnello. "We don't know why they've recently come to apples." Affected trees seem to be those under stress, especially those enduring wet conditions and waterlogged soils or suffering from winter injury or fi re blight. The insect is attracted to trees that give off ethyl alcohol—which trees do as a reaction to stress. Once in an orchard, the insects seem willing to attack healthy trees as well, though they may be focusing on trees that appear healthy but have been stressed by the hard winters of the last two years. Unlike other borers that aim their attack at the base of tree trunks, black stem borers make a line of holes up The growing threat of Years after invading from Asia, the insect is emerging as an apple tree pest. by Richard Lehnert BLACK STEM BORER

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