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Aphid damage on an Ash leaf
Curled leaves, a sooty black mold and a sticky substance falling from the tree are all indicators of an aphid infestation. While there are around 50,000 aphid species worldwide, most will feed on specific hosts. This prevents them from feeding indiscriminately in the landscape. For example, the Pine Bark Aphid feeds on pine limbs and trunks. Another plant specific aphid species is the Woolly Beech Aphid. It attacks the European Birch tree. Other aphids are less discriminating and will feed on a variety of plants. The Green Peach Aphid can be found on both Peach trees and vegetable plants.

Aphids vary in color and size, due to the large number of aphid species.  Typically, tree feeding aphids are pinhead size and green in color. But this is not true in every case. For example, an aphid that attacks Willow trees is the largest of the aphid species. It’s also not uncommon for the same aphid species to be different colors on the same tree host. Causes for this could be temperature, crowding or food quality.

Aphid damage is primarily cosmetic and doesn’t usually harm the life of the tree. The sticky substance created by aphid feeding can become a nuisance, when very large numbers of aphids are present. This can coat sidewalks, outdoor furniture and anything else that is under their host. Aphid control depends on the severity of the infestation. The aphid does have a number of natural predators that may keep the number of aphids in check. In Illinois, the multicolored Asian Lady Beetle and native lady beetle will feed on large numbers of aphids when present in the landscape.

Keep in mind that healthy trees are much less susceptible to long term aphid damage. Proper fertilization and watering practices go a long way in protecting trees. Contact the Plant Health Care Department at KTS to discuss specific problems and solutions.  Learn more about aphids or other pests and control measures on our Pest Controls page.

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