Fall webworms at the end of pecan tree limbs. Photo: G. Keith Douce, U. Georgia, Bugwood.org.
Rose is looking toward the spring growing season, and asked, “Is there anything that can be used on pecan trees early on to prevent the [fall] webworms and bagworms from entering into the pecan trees?... I have done some research from time to time but have not been able to come up with anything definite. If you have any suggestions, it would be of great help.”
If the tree is non-bearing young or very old, then the easiest solution is to make an insecticidal soil drench. AHA has used Martin’s Dominion™ tree and shrub insecticide. The insecticide is mixed in a bucket and poured around the base of the tree. As always, follow the directions for mixing and application. This treatment is most effective before a tree leafs out, and pecan trees tend to be the tree with the latest leaves.
The soil drench is also suitable for treating bagworms on junipers, cedar, and Leyland cypress trees.
Dr. Mary Helen Ferguson, a Horticulture Agent with the AgCenter, also shares these tips for managing fall webworms, “When fall webworm webs are low enough to reach with loppers or a pole pruner, and only one or a few limbs are affected, one option is to just cut out the webbed limbs. Another option is to break up the webs, so that natural predators like birds can get to the caterpillars more easily.
There are insecticides that will kill fall webworms, but it’s often difficult for people to spray effectively for them. The webs may be too high to reach. Even if they’re not, the pressure provided by home spray equipment may not be adequate to penetrate the webs and reach the caterpillars.
If you find fall webworms on your plants earlier in the growing season in future years and decide to spray an insecticide, it’s still best to break up the webs so that the spray will be more likely to reach the webworms. Quite a few insecticides are effective on caterpillars. To minimize damage to beneficial insects, insecticides with active ingredients like Bacillus thuringiensis subsp. kurstaki and spinosad can be used while fall webworms are small. Other active ingredients with efficacy against caterpillars include acephate, carbaryl, and several the pyrethroids (names ending in "-thrin," plus esfenvalerate). Make sure any insecticide you use is labeled for use on the type of plant on which you plan to use it and be sure to read and follow label directions.”
Gooseneck loosestrife, a potential weed. Photo: NC State Extension.
Susan asks a very responsible question about a non-native plant, “Do you know if [gooseneck loosestrife, GL] is considered invasive in LA? I cannot an invasive species list.”
The Invasive Plant Atlas of the United States, www.invasiveplantatlas.org, has a map showing GL as an invasive plant in the Midwest and in the Northeast, but not in Louisiana.
Dr. Hallie Dozier, a forestry professor with the LSU AgCenter, is familiar with invasive and nuisance plants, and she responds to Susan’s question, “It can be very weedy in a garden setting, to the point where after a few years gardeners are ready to pull out every plant, so I imagine it will be a problem eventually in our wetter areas. I understand that on top of its beauty, it has food and medicinal properties.”
Louisiana Vegetable Planting Guide. Image: LSU AgCenter
Lori is also looking forward to the spring garden season and asks about AgCenter’s recommendations, “I see where there are cultural recommendations for planting times in the [AgCenter’s] Vegetable Planting Guide. My question is where the dividing line for is north and south. I’m in Baton Rouge so should I follow north or south guidance?”
Lori would use the planting recommendations for southern Louisiana because of Baton Rouge’s proximity to the Gulf Coast. However, what recommendations should a gardener in central Louisiana follow, north or south. The answer depends on the gardener. If a gardener is a risk-taker, then follow the earlier planting dates for the south and hope to avoid a cold snap. This gardener may be able to enjoy an early harvest of fresh vegetables.
If a gardener is risk-averse and wants to avoid replanting a garden due to possible freeze damage, the planting dates for north Louisiana would be the safe path to take.
If you want to contact Roots, Shoots, Fruits and Flowers, please send your questions and pictures to Keith Hawkins, Area Horticulture Agent (AHA), 337.284.5188 or firstname.lastname@example.org.
“Before you buy or use an insecticide product, first read the label, and strictly follow label recommendations. Mention of trade names or commercial products in this article is for informational purposes only and does not constitute endorsement by Louisiana State University AgCenter.”
“This work has been supported, in part, by the USDA National Institute of Food and Agriculture, Renewable Resources Extension Act Award, Accession Number 1011417.”