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Insects of the Fall Months

Contributed by:  Mallory Kelley, Regional Extension Agent

Fall Webworms and Asian Wooly Hackberry Aphids

Many calls and questions have come in about two insects in particular this month.  First, the webbing that many people see in trees this time of year indicate the presence of fall webworms.  These worms have been known to web in over 85 species of trees in the United States and in our area are most commonly seen in, but not limited to; oaks, pecans, cherry, willow, and river birch.

 Fall webworms become very visible in late summer and fall and create silken nests around leaves at the ends of branches.  All of the feeding from the webworms occurs within the silken nests and last approximately six weeks and if food runs out new foliage will be encased.                                  

Though the webs are very unsightly, damage to most trees is considered to be insignificant and especially if it is occurring close to fall when the trees will naturally be losing their leaves with the change of the season. One of your best measures of defense is sanitation.  As limbs, nuts and leaf debris drop from the tree, clean this up to reduce sites for the insects to overwinter on the ground and come right back next year. As always, less stress to the trees throughout the year will make them less susceptible to the attack of insects and disease issues.

The second insect that has caused a great concern this month has been the Asian Wooly Hackberry Aphid.  We as southerners are very familiar with the aphid, but this aphid has a little different appearance than what we are used to. Not seen in these great numbers every year, this insect has been described in central Alabama as hot dry “snow” but even if you have not seen them you might still be asking yourself,  “Why is this sticky stuff getting on my car?” and “What’s making my trees turn black?”

The Asian wooly hackberry aphid is one of the many relatively new pests that have been accidentally introduced to the state.  Adults are about 1/16 inch long and are covered with a white, cotton-like waxy material that makes them relatively easy to identify. Adults may be winged or wingless. During the past few weeks large numbers of winged adults have been seen in areas where there are a lot of hackberry trees.

Both adults and nymphs produce large amounts of honeydew, which accounts for the sticky accumulations on vehicles parked beneath hackberry trees. Heavy infestations of this pest can cause trees to defoliate prematurely. There is little risk of this pest attacking other plants.

While this insect can be controlled with sprays, few homeowners have the equipment needed to apply treatments to mature trees. Even when equipment is available, foliar sprays are often not an option because of the drift onto adjacent property. For now, the best approach is to live with the situation. They will go away in a few weeks.