Bare limb tips and clusters of webbing in pecan trees are often the first sign that fall is right around the corner.
This webbing is caused by clusters of the larvae of the Fall Webworm (Hyphantria cunea (Drury)) which is often also called Pecan Webworm. “Fall Webworm” is a bit of a misnomer in our region since they are able to strike in spring and summer thanks to our long growing season. They are most noticeable in the fall thanks to cumulative effects of earlier feeding.
The adult form of the fall webworm is a solid white or white and brown spotted moth that emerges in late March through August in southern climates. After mating they lay orderly clusters of green eggs, usually May through August. Soon after emergence, the larvae begin creating silk webs to protect themselves as they voraciously feed on their various host plants, of which Pecan is most common in Northwest Florida gardens.
Although they are capable of defoliating complete trees, especially smaller ones, most seasons they are kept in check by beneficial insects such as the paper wasp. It is beneficial for small orchards or home growers to scout their trees from June through August. If small webs are observed in young trees, it is best to prune them out with a pole saw or pole pruner and dispose of the branch. Pruning of small branches does not harm the tree, but it may be of no benefit to remove small webs in larger trees, if they are being controlled by natural enemies.
Most home gardens don’t have a practical ability to spray for this insect. For homeowners it is difficult to spray for control, due to the cost of the equipment required to get the spray into the tree canopy. If spraying is an option, many insecticides containing spinosad or Bacillus thuringiensis (Bt) exist. Both of these products target caterpillars while not harming beneficial insect predators that feed on these worm populations. Several more toxic insecticide products exist that will control fall webworm, but they often exacerbate insect problems by killing off beneficial insects that might be controlling other insect pests.
Fall webworm is not usually a serious problem for home gardens. Let natural enemies take care of the problem in most cases.
Pecan trees are well adapted to our area, making beautiful large shade trees. And, if the correct varieties are planted, they can provide pecans.
Only those pecan varieties that show some real resistance to disease problems are recommended for planting here in the humid south. Select grafted trees of Desirable, Curtis, Elliott, Moreland or Stuart varieties.
Pecan leaves and fruit. Photo credit: Brad Haire, University of Georgia, Bugwood.org
Obtain and plant your pecan trees during the winter – December through February. Purchase trees that are three to six feet tall. Larger trees are more difficult to transplant.
Give pecan trees plenty of room to grow. The distance between trees should be approximately sixty feet because mature trees are quite large. Commercial producers sometimes use a closer spacing, primarily because they are using varieties that will bear at an earlier age. But most of those varieties do not have good disease resistance and still require pesticide spray at times. Homeowners will not have the needed equipment to spray a large pecan tree and the drift from such sprays would not be desirable around your home, so commercial varieties aren’t recommended for home plantings.
One of the keys to survival of a pecan tree is not allowing the root system to dry out before, during or after transplanting. Regular watering will be required for a period of at least six months or until the young tree is well established. The planting hole should be 18 to 24 inches wide and only as deep as the root system. Spread the roots so they are not matted together. The planting depth is critical. Place at such a depth that the uppermost root is at or near the soil surface. Excessively deep planting can result in eventual death of the tree.
When planting your tree, there is no need or advantage to using peat moss, compost, manure or other organic matter in the planting hole. Plant the tree in the native soil without amendments.
Do not fertilize when the tree is planted. Wait until May of the first year after planning to apply fertilizer.
Remember that pecan trees are large at maturity, with branches spreading 30 feet or so from the trunk. Also, because of the brittle limbs and failing nuts, it’s best not to plant these trees too near the home, driveway or sidewalk.
Panhandle residents have seen caterpillars in abundance this June. One common visitor to pecan trees is the Walnut Caterpillar Datana integerrima. The walnut caterpillar has a very narrow host range and feeds only on trees in the Juglandaceae family which includes walnut, pecan, and hickory trees. They are sometimes seen on other plant material, but feeding on non-host plants is unlikely.
Walnut caterpillar feed on the leaves of host trees through several growth stages and molts until they have reached the final larval instar and are ready to pupate into an adult moth. Their color changes from light green when newly hatched to reddish-brown to almost black with long white hairs as they mature. The caterpillars group together in large masses and may hang from each other and dangle from the tree branches when molting. Instead of creating a cocoon in the tree, the walnut caterpillar moves to the ground beneath the tree and burrows into the soil or leaf litter to pupate and emerges later as a moth.
What can you do if your pecan tree is hosting walnut caterpillars?
Although the numbers seen on trees may be alarming, a healthy tree can tolerate some feeding damage. Stripped branches may increases the chance of a lower yield of fruit because the removal of leaves does reduce the amount of energy the tree can produce, but overall health of the tree should not be significantly affected. However, many homeowners find falling caterpillars and their excrement unappealing and may decide to take steps to manage the population.
There are several natural enemies that feed on caterpillars, so avoid using a broad spectrum insecticide that might harm predatory insects and other animals. Consider using a biological control product such as Bt (Bacillus thuringiensis) that is only lethal to caterpillars. Other methods are “pick and squish” or drowning in a bucket of soapy water. Next year, in the spring, watch for masses of tiny green eggs on the underside of leaves and remove and destroy them before hatching.
For more information visit USDA Forest Service Forest Insect & Disease Leaflet 41 “Walnut Caterpillar”
Florida Pecan Field Day and Florida Pecan Growers’ Association Annual Meeting
Jefferson County Extension Office 2729 West Washington Street
Monticello, Florida 8:30 AM, EDT
Thursday September 5th
Harvest time is coming for Florida pecan growers. Demand is up, irrigation needs are down, and fungus pressure has been a serious problem over the entire Southeast.
Producers will meet in Monticello on Thursday, September 5 for the annual field day and Pecan Growers’ Association meeting. If you’re a pecan grower, or just considering it, the morning’s topics and speakers will be a great opportunity to learn more about the pecan business.
The agenda is below. For more information, contact Jed Dillard at 850-342-0187 or firstname.lastname@example.org. Please make a lunch reservation by noon Tuesday, September 3.
- 8:30 Registration
- 9:00 Welcome……… Mark Brown, President Florida Pecan Growers Association and Jed Dillard, Jefferson County Extension Agent
- 9:10-9:45 “Florida Water Policy and Its Impending Effects on Pecan Production” ……. Carlos Herd, Director Division of Water Supply, Suwannee River Water Management District
- 9:45-10:15 “Management strategies and tactics for suppression of pecan arthropod pests: chemicals, trap crops and everything in between.”
- Dr. Russ Mizell, University of Florida Entomologist, Quincy
- 10:05-10:35 “Controlling scab and other pecan diseases” Dr. Tim Brenneman University of Georgia Department of Plant Pathology
- 10:35-10:55 Break
- 10:55-11:25 “Tree Spacing, Alternate Tree Pruning and Removal, and Tree Transplanting”. Dr. Lenny Wells, UGA Extension Pecan Specialist, Tifton
- 11:25- Noon “Direct Marketing of Pecans – What do I need to Know?”…………..Elena Toro, Suwannee County Extension Agent
- Noon…………… Sponsored Lunch
- 1PM Annual Meeting Florida Pecan Growers’ Association
- 1:15 Tour (Tentative)
- CEU’s: two half ceu’s for ag row crop, tree nut, private applicator and demonstration categories
It is that time of year where mysterious webs have invaded pecan trees throughout the Southeast United States. This is definitely the case in the panhandle of Florida. Many have called into the extension office asking for identification of the web mass in their pecan trees. It is the Fall Webworm that has made a home in the pecan tree this fall.
Photograph by James Castner, University of Florida.
Photograph by Andrei Sourakov, University of Florida.
The adult fall webworm is a moth that is bright white in color and may have darker spots on its wings. The larvae of the moth are what lives in the tent web masses. Immediately when the larvae webworm hatches out of the eggs it begins to create its webs around foliage in which it will feed on.
The damage cause by the feeding of the larvae on the pecan trees is isolated to the leaves and they will not eat the nuts. If Defoliation is severe enough it can reduce the current years crop and the following years crop. Several years of defoliation can lead to death of the tree but this is not likely. Obviously the webs are ugly as well and if the tree is not only a producer of pecans but also functioning as an attractive shade tree in a ornamental since this can be a problem.
In most commercial pecan production settings webworms are not very prevalent because of the spray programs implemented. For residential settings the best solution is to manually prune them out because of the lack of proper spray equipment to cover the entire tree. If the problem is bad enough call your local extension agent to get recommendations on products that could be used.
Andrei Sourakov and Thomson Paris (2011, April) Fall webworm,Hyphantria cunea (Drury) (Insecta: Lepidoptera: Arctiidae: Arctiinae). Retrieved from http://edis.ifas.ufl.edu/pdffiles/IN/IN87800.pdf
Michael J. Hall. Fall Webworm. Retrieved from http://www.lsuagcenter.com/NR/rdonlyres/68665E57-A2F4-4030-A4E6-55821DCFBDD6/16783/FallWebworm_sheet_.pdf