Hackberry (Celtis occidentalis) is a native tree of the U.S., and is also known as common hackberry and nettletree. The tree grows in hardwood forests and limestone ground in its native habitat. Hackberry has a mature height of 40 to 60 feet with a 1- to 2-foot trunk diameter. The foliage is elm-like and the bark is corked and warty. Hackberry trees are susceptible to number of problems.
Hackberry trees are susceptible to infestation from the hackberry woolly aphid. The Asian native pest is also referred to as the Asian woolly hackberry aphid and it primarily infests the Chinese hackberry. Armillaria root rot is a likely fungal disease of hackberry, and is caused by Armillaria mellea.
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Hackberry woolly aphids are very small, soft-bodied pests with a bluish white wax coating over their yellow, gray or green bodies. Some varieties of the pest have wings with black borders. The insects have antennae with light and dark bands. Armillaria root rot is also referred to as oak root rot or shoestring disease. The soil-borne fungus infects a wide range of conifers and broadleaf trees.
The aphids infest the lower sides of leaves in large numbers, creating small globs of fuzzy mass. The insects feed on the sap from the leaves and secrete sticky honeydew that in turn encourages the growth of black, sooty fungus on infested tree areas. The foliage of trees infected with armillaria mellea starts to discolor and drop prematurely. This is followed by branch dieback near the top of trees. Mushrooms often sprout near the tree base and fine, reddish-black, root-like growth appears on the root crown.
It is not necessary to use insecticides on trees to get rid of the hackberry woolly aphids, since the pests are not harmful to tree health when they occur in small numbers. However the sooty fungus is an aesthetic disorder and ruins the appearance of trees. Use insecticidal soaps or horticultural oils to control pests when they increase in number. Prevent chances of armillaria root rot by planting the tree in a well-drained site and avoid over-watering. Use disease-resistant tree varieties and avoid planting in areas where the fungus has been a problem before. There is no cure once trees are infected.