MOUNT VERNON — Knox County horticulture has another pest to worry about. Bagworm infestation has been encroaching into Knox County over the last couple of years and now seems to be firmly entrenched. Bagworm generally attacks arborvitae, juniper, pine, spruce and several other evergreen species. It has also been known to attack certain deciduous trees such as black locust, honeylocust and sycamore.
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“The biggest problem is,” said Troy Cooper of the Knox County OSU Extension, “right now is the worst and most ineffective time to be treating this insects, unfortunately.”
Eradication is difficult because the presence of the pest is usually not detected until the bags appear. The cocoon begins to appear this time of year and is basically impervious to pesticides and other chemicals at this stage.
“Once that caterpillar gets in to cocoon there’s nothing that will kill it,” said Fred Forster, owner of Glass Gardens Greenhouse. “It’s sort of God’s protection for the insect.”
Forester also agreed this is not a good time to try to eradicate the pest.
“Right now it’s in the cocoon and it will be coming out soon,” he said. “Then you’ll have an effective spray. It won’t do any good to spray while it’s in the cocoon.”
The caterpillars hatch sometime in early June and exit from the bottom of the cocoon and begin feeding and creating the characteristic bag from which they derive their name.
“We really want to get that word out as early as we can,” Cooper added. “In late June or early July get out there spraying.”
Bacterial sprays and certain pesticides have shown the highest effectiveness in combating a bagworm infestation. These pesticides may require special handling and application techniques. Therefore, any attempt to use this method by someone not familiar or trained to use the pesticides should not be made without contacting an expert.
The bagworm has become more of a problem in recent years. According to Cooper the pest has moved up from southern states slowly but surely.
“I’m willing to bet that over 90 percent of the yards in Mount Vernon with evergreens had bagworms last year,” Cooper said. “They were that prevalent.”