Got cones? Bagworms
A customer once told me they thought those little brown things on their Leyland Cypress trees were “pine cones”. I ask, have you ever seen pine cones crawling up and down the tree limbs? Have you seen a evergreen tree literally pulsate overnight as these crawlers devour it?
Bagworms can be deceptively destruction and are native to the US. They are particularly damaging to arborvitae and junipers.
The following is paraphrased from Cliff Sadof and Marc Rhainds, Department of Entomology, Purdue University
As the summer approaches, homeowners who had their trees defoliated by bagworms last year are getting prepared for this year’s round of plant destruction. Bagworms are caterpillars that strip the leaves from a wide variety of trees and shrubs. Most commonly they devastate dense plantings of evergreen spruces, pines and arborvitae used as visual screens or windbreaks.
Bagworms get their name from their unique habit of hiding from birds by gluing bits of leaf on to the silken bags in which they live. At this time of year, they are in the egg stage concealed in last year’s brown bags that are hanging from trees. In mid May and June the eggs will hatch into small caterpillars that will make new silken bags to be covered by freshly cut leaves.
For the past 10 years, the relatively mild winters have caused bagworm problems to increase in severity and move northward. People in these communities have been learning the importance of inspecting their plants in the month of June for these small bags, and spraying them with a foliar insecticide to kill the caterpillars before too much defoliation occurs.
There are two ways to determine whether or not a bagworm infestation is present. The easiest way is to wait until the eggs have hatched and inspect host plants for small bagworms feeding on leaves. The second way is to cut open the bags to reveal the body of the female. Then, break apart the female and examine the eggs. If the eggs are creamy white, the eggs are viable and will hatch into caterpillars that will feed on the overwintering host plants. In this case treatment is needed. If eggs are brown the eggs are dead and no bagworms will be expected to hatch and no treatment will be needed.
“One way of killing bagworms is using manual methods. You literally pick the bagworm nests, which look much like pinecones, off the tree or bush. After you pick them destroy them. Burning is best to make sure they are dead and won’t spread to another part of your yard.
Another method to kill bag worms is to attract birds to those trees. Hang bird feeders or home made bird feeders from those trees infected. There are many low cost bird feeders like the pinecone feeder that can be made. Cover the tree or bush with these if you really want more birds. Be sure to have a water source for them nearby. For many pest problems in trees this is a great option.
Lastly, you can use insecticides to spray the tree to help treat the bagworm problem. There are certain times of the year that these needs to be applied to deal with this type of pest problem. If you have had this infestation in the past, be sure that you treat your trees and bushes at the proper times of the year to prevent this problem.”