Springtime Tent Caterpillars and Fall Webworm and Bagworm
People have nothing on bugs when it comes to using bags and tents for protection while sleeping. Some caterpillars have similar methods to protect them from the elements and from the voracious appetites of birds.
The Eastern Tent Caterpillar appear early in the season, usually in late April. The egg masses are easy to spot in the fall after the leaves have dropped. They will appear as shiny, dark gray foam wrapped around the twig. In the spring the larvae gather at a fork in a tree and build a light, grayish white web-like tent. Tent Caterpillars like to feed on wild cherry, crabapple, plum and peach to name a few. One or two colonies can completely defoliate a small tree. Since this defoliation occurs early in the season, the plant must expend much energy in setting out new leaves thus enhancing the possibility of weakness. I remove the nests in the spring with a gloved hand and paper towel. I then burn the mess to make sure nothing lives. You can also drop them into a bucket of hot, soapy water. Because most caterpillars will be in the nest, late afternoon or early morning is best to remove them from the tree.
The fall webworm appears on trees in late summer and early fall. Fall webworms enclose leaves and small twigs in their light gray, silky nests which are usually located at the tips of branches. These larvae have been known to feed on over 85 different species of trees in the United States. This pest overwinters in the pupal stage in the ground but can also be found in the debris of old nests and under loose bark. The adults emerge from late May into July. Nests can be pruned out of small to medium trees. Parasites and predators. such as wasps, birds, predatory stink bugs and parasitic flies, may control the worms biologically in larger trees where you can’t reach to remove them. If using insecticidal sprays, keep in mind that the spray will be detrimental to the natural predators of the webworms.
Bagworms pass the winter as eggs and hatch in early to mid June. They are actually the larval or caterpillar stages of moths. After hatching, they spin a cocoon-like bag and attach bits of plant matter, usually leaves, onto it. They have a brownish-gray color. They start out about an eighth of an inch long and feed for about six weeks, enlarging the bag as they grow, ending up to be about two inches long. Bagworms prefer juniper, spruce, arborvitae, pine and cedar but have been known to attack deciduous trees. Bagworms mature in late August or early September. Older larvae strip evergreens of their needles and devour whole leaves of deciduous species leaving only the larger veins. When abundant they can defoliate a plant and heavy infestations over several years, especially when coupled with other stresses such as drought, can kill that shrub or tree.
Inspect trees and shrubs starting at the beginning of June. If only a few plants are affected, handpicking and destroying the attached bags by placing them in a bucket of soapy water may provide sufficient control. If an insecticide is needed, the best time to apply it would be in the early stages while the larvae are small, usually in early July. Be sure to always follow label directions. There is a type of bacteria that is often called Bt, Bacillus thuringiensis, which only kills certain insects and does not affect humans or animals. It needs to be applied early June to mid July because it works best on bagworms when they are young.
As always, Happy Gardening!
More information about gardening and related subjects is available online at http://www.hort.purdue.edu/ext/garden_pubs.html The Purdue University Cooperative Extension Service can be reached at 499-6334 in LaGrange Co., 636-2111 in Noble Co., 925-2562 in DeKalb Co. and 668-1000 in Steuben Co.
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