Summer has come to an end and the cooler days of fall are finally here. BUT ... This doesn't always spell the end of insect problems in the garden. Some pests persist in the garden even in the fall and others are just beginning to become a nuisance. Below are some to watch out for ...
Fall webworms are often confused with tent caterpillars since they both build web nests in trees. However, tent caterpillars appear in the spring and fall webworms usually appear in the late summer and early fall.
They also have very different styles when it comes to building their nests. Tent caterpillars build compact nests in the crotch of two branches, while the fall webworms build large silken webs which surround the foliage at the tips of branches. As the caterpillars exhaust the leaf supply within the web, they enlarge it to incorporate a new supply of fresh green foliage and the nest expands along the branch.
Fall webworms attack many different species of trees including pecan, walnut, hickory, many types of fruit trees, and the eastern redbud. These caterpillars have a voracious appetite and feed on the tissue between the leaf veins, leaving behind webs filled with brown skeletonized leaves and green frass (their droppings). This is not at all attractive in the landscape.
In general, webworm feeding doesn't hurt the tree because the damage is usually localized to just a few branches and since it occurs later in the season, the tree has had time to store food. The damage is mostly cosmetic and the webs will eventually weather away over the winter. However, if the tree is under stress due to drought, poor nutrition, or repeated defoliation from multiple generations of caterpillars, then its health could be in jeopardy and control measures may be warranted.
In many cases, the unsightly nests of fall webworms can simply be removed from small to medium sized trees by pruning out the infested branches.
You can also control them by spraying a liquid formulation of the bacteria, Bacillus thuringiensis (Bt). Bonide Thuricide (BT) Liquid, applied to the foliage right next to the nest, will kill the caterpillars when they expand the nest and eat these leaves. Bt will not harm beneficial insects. Bonide Captain Jack's Deadbug Brew, another naturally derived organic insecticide, is also an effective control when sprayed on the foliage adjacent to the web.
The foliage and caterpillars inside the nest are protected by the web and spraying the nest is usually not effective. The trick with these sprays is to cover the foliage that the caterpillars will be eating. Always read and follow the label directions when spraying any pesticide.
The Brown Marmorated Stink Bug (Halyomorpha halys) has not only become an annoying invader of our homes but their populations have exploded to the point that they have become a major threat to many agricultural crops including both ornamentals and food crops. Because this particular species of stink bug is having such an impact on fruit and vegetable crops, a lot of research is being directed towards developing control methods. Some of this research is focusing on natural enemies and pheromone traps in addition to chemical controls.
Late September and October is the time of year that these nasty pests begin to congregate around the windows and doors of our homes seeking entrance to a nice warm, cozy, place to spend the winter.
Exclusion is one of the best preventative measures for controlling populations indoors. Carefully examine the foundation and around windows and doors for cracks and crevices where they can sneak into the house. They will seek out these entry points in an attempt to find overwintering sites. Use caulk and weather stripping to seal any cracks.
Bonide Household Insect Control kills stink bugs on contact but also has a four-month residual that creates a relatively effective barrier around windows, doors, and other areas where they might gain entrance to your home. This product also acts as a repellent.
Another product that is highly effective on stink bugs is Bonide Cyper-Eight, which contains Cypermethrin. This kills on contact with a very long residual. It has an indoor and outdoor use label and is recommended by a lot of commercial pest control operators and universities.
The boxelder bug is another nuisance insect that can invade your home in droves at this time of the year. Like the stink bugs, they are seeking protected overwintering sites and your warm home fits the bill perfectly! I always see swarms of the bright red immature boxelder bug nymphs crawling over the concrete statues and surrounding plants in the Viette gardens at this time of year. I guess the concrete warms up in the sun and they take advantage of this late season warmth the same as they do when they are swarming on the foundation of your house. Creepy!
Control of these invading insects is similar to that for the stink bugs. Since they also sneak into the house through cracks and crevices in the foundation and around windows, doors, and air conditioners, sealing these with calk and weather stripping will do wonders in keeping them out of the house. Bonide Household Insect Control with deltamethrin is very good at controlling these unwanted pests. Use only according to the label directions.
The azalea caterpillar (aka the red-headed azalea caterpillar) is a colorful caterpillar that feeds mostly on azalea foliage but will also attack blueberries, apple trees, and red oak trees. They tend to feed in large groups and can quickly defoliate their target plants if they are not controlled.
See my blog post for more information about these destructive caterpillars.