Those loose, grayish-white webs wrapped around your branch ends are fall webworm. Early August sits inside the window K-State flags as the noticeable one, late July through late September. K-State Research and Extension is direct about the stakes: heavy feeding can completely defoliate a host tree, but it doesn’t kill it. The webs look worse than the damage underneath. Pruning out the webbed tips while nests are still small is the standard response. K-State also lists leaving the webbing alone as a legitimate option on ornamental trees. Control there is optional.
What’s wrapped around the ends of my branches right now?
Fall webworm caterpillars build a silk web around the ends of branches, enclosing the leaves inside it. That web collects the caterpillars’ own droppings, which is part of why the nests look so ragged. K-State Research and Extension describes how it grows. Larvae start with a small web near a branch tip. They expand it as they need more foliage. Kansas has two races of fall webworm, blackheaded and redheaded, and each one runs two generations a year, for four generations total. Early in the season the two races stay staggered and distinct. By late summer, K-State says moth activity overlaps enough that one generation becomes hard to tell from another. That overlap is why a fresh nest in early August doesn’t sort neatly into a single generation anymore. K-State’s general guidance places the more visible generation in the field from late July through late September. That window covers a nest that showed up the first week of August.
Is fall webworm going to kill my tree?
No. K-State Research and Extension states plainly that high fall webworm populations can defoliate a host plant completely. They do not kill it. K-State’s entomology team adds a qualifier: the damage usually isn’t directly harmful to the tree, especially a larger one. A smaller infested tree may just look worse by comparison.
Pecan is the one real exception. K-State notes that uncontrolled webworm can cut into pecan nut production and quality, since pecan is grown for its crop rather than its shade. Control matters more there than on an ornamental tree. On ornamental trees generally, K-State’s own guidance calls control optional.
Not sure if what you’re seeing is normal wear on an established tree, or real strain on something young? A tree health assessment gets you a straight answer instead of a guess from the ground.
Fall webworm vs bagworm vs eastern tent caterpillar vs mimosa webworm: how do I tell them apart?
Four different pests build four different kinds of webbing on Kansas trees. Mixing them up leads to the wrong fix. Here’s how they line up.
| Pest | Where the web sits | Trees it hits | When it shows up in Kansas | What to do |
|---|---|---|---|---|
| Fall webworm | Encloses the ends of branches and the leaves inside | Almost all fruit, shade, and ornamental trees except conifers: birch, cherry, crabapple, elm, maples, hickory, pecan, mulberry, walnut, willow | Two generations per race, four total across Kansas’s two races; the more visible generation runs late July through late September | Prune out webs while they’re still small; spraying is a last resort and has to penetrate the webbing to reach larvae |
| Bagworm | Individual spindle-shaped bags, 1 to 2 inches, hanging off branches | Conifers hit worst: arborvitae, cedar, fir, juniper, pine, spruce | Single generation; eggs hatch mid-May to early June, feeding runs about three months | Hand-pick bags; sprays only work on small larvae in late May and June, not by August |
| Eastern tent caterpillar | Small silken tent built into the crotch of a branch | Wild cherry is the favorite; also ornamental shrubs, shade, and forest trees | Single generation; larvae hatch as trees leaf out in early spring and finish feeding by about mid-May | Usually best ignored by the time the tent is noticeable; pull an objectionable web mass off by hand or twirl it onto a pole |
| Mimosa webworm | Webs leaves together at the ends of branches | Honey locust and mimosa | Two generations per year in Kansas | Selective pruning removes isolated early infestations; once a tree is heavily webbed, K-State says it’s too late to spray |
The location of the web is the fastest way to sort these out. A web wrapped around a branch tip, on a tree that isn’t a conifer, is either fall webworm or mimosa webworm. The host tree usually settles which one. Honey locust and mimosa point to mimosa webworm. Almost anything else points to fall webworm. A web built into a fork or crotch, rather than at the tip, is eastern tent caterpillar. Individual hanging bags on a cedar or juniper are bagworm, and bagworms in Topeka run on their own spray-timing calendar. By August, spraying for bagworm is already too late. Fall webworm isn’t on that clock yet. And if there’s no web at all, just leaves chewed into irregular holes or a lacelike skeleton, you’re likely looking at beetle feeding rather than a caterpillar. Our guide to Japanese beetles in Topeka covers how to confirm that one.
What do fall webworm caterpillars actually look like up close?
Mature fall webworm caterpillars are yellowish with black and brown markings, with tufts of long hair. K-State’s entomology team describes a wider color range: pale green to yellow to nearly whitish, with two black spots on each abdominal segment. Kansas’s two races are told apart by head and tubercle color, not by body color. Blackheaded larvae carry black head capsules and bumps. Redheaded larvae run reddish to orange in the same spots. Both races are hairy, with long body hairs covering the caterpillar.
One feeding habit separates fall webworm from eastern tent caterpillar. Fall webworm larvae stay inside the web to feed, expanding it as they need more foliage. Eastern tent caterpillars leave the nest to forage and return to it at night or in bad weather. That difference is about feeding, not about whether a caterpillar ever leaves the nest at all. Late in the season, mature fall webworm larvae do leave the web. They crawl down toward the soil or plant debris to pupate. A wandering caterpillar on the trunk or ground in late summer can still be a fall webworm, just one that has finished feeding.
Why is this only showing up now, in August?
Fall webworm runs two generations a year within each race, and the first is small enough that most homeowners never notice it. Adult moths emerge from overwintering pupae in spring. They mate, and females lay egg masses of 400 to 500 eggs on the undersides of leaves. That first generation feeds for four to six weeks and usually goes unnoticed. The second generation is much larger and far more visible. K-State places it in the field from late July through late September, exactly the window this is. By now, K-State says the two Kansas races have overlapped enough that telling one generation from another gets hard.
Where the tree stands plays a role too. K-State notes that fall webworm shows up more often on isolated trees than on trees grouped together. That describes a lot of the open, larger lots around Rossville and the smaller towns on Topeka’s edges. K-State also documents heavier infestations in eastern and southern Kansas. Shawnee County sits squarely in that eastern band. Catching an infestation like this before the second generation gets large is the point of walking the yard on a regular schedule. A spring tree health checklist covers that in more depth.
What should I actually do about the webs on my trees?
Prune out the webbed branch tips while the nests are still small, then dispose of what you cut. K-State lists this as a common control practice. Its entomology team calls pruning the most effective way to deal with an infestation, since the caterpillars stay enclosed inside the web you’re removing.
For a web that’s out of easy reach, a pole with a nail through the end works. Insert it into the web and twist the pole. The silk wraps around it, so you can pull the whole nest free and destroy it.
Skip the ladder if the webs are high in a mature tree. A tree trimming crew can reach those branch tips safely, without the risk of a homeowner’s ladder.
Chemicals are a last resort. Timing matters if you go that route: sprays need to go on while webs are still small, before much foliage is gone. Spraying the outside of a web mass won’t kill the larvae inside it. A high-pressure sprayer has to punch through the webbing itself to reach them. Spinosad, cyfluthrin, and permethrin are the active ingredients K-State lists for control. As K-State puts it, the end user must read individual product labels to ensure safe and proper use against the intended pest.
Once the webbed branches are down, sorting out where the debris goes is worth handling the same day. Otherwise you’re left with a pile of cut branches sitting in the yard.
If webworm turns out to be one of a few things going on in the canopy this season, an arborist consultation is worth it. It covers the whole tree, not just the one visible problem.
Frequently asked questions
Do fall webworms come back on the same tree every year?
They can, especially on a tree standing alone rather than grouped with others. Mature larvae from the second generation crawl down and leave the web to pupate. They shelter in the soil or under plant debris through winter. Adult moths emerge from those overwintering pupae the following spring. That puts next year’s first generation right back where this year’s caterpillars started.
Will cutting the webbed branches hurt my tree?
Removing a handful of branch tips has little effect on a healthy, established tree. That’s exactly why K-State lists pruning as the standard control method. It’s a much smaller intervention than letting the web keep expanding. Larvae increase the size of the web as they need more foliage.
What trees in Topeka yards are most likely to get fall webworm?
Birch, cherry, crabapple, elm, hickory, maples, mulberry, pecan, walnut, and willow are named hosts in K-State’s Kansas guidance. A K-State survey of infested trees around Manhattan, Kansas counted nests by host species. Walnut, mulberry, elm, flowering crab, osage-orange, and redbud carried the highest counts. Walnut had 25 nests. Mulberry had 29. Elm had 20. Flowering crab had 12. Osage-orange had 8, and redbud had 14. Osage-orange and redbud are worth flagging, since neither one appears on the general host lists. Almost any fruit, shade, or ornamental tree can host fall webworm. Conifers are the one group left alone entirely.
Should I spray my whole tree just to be safe?
No. K-State’s own guidance treats control as optional on ornamental trees. Pecan is the exception, since uncontrolled webworm can cut into nut production and quality there. K-State also notes it isn’t necessary to spray a whole tree over just one or two nests. Pruning out the visible webs handles the ornamental case directly. That skips the high-pressure sprayer needed to punch insecticide through the webbing on a large colony.
Can fall webworm spread from one tree to another in my yard?
Not by caterpillars crawling from tree to tree. Larvae stay inside their web to feed, expanding it to enclose new foliage. The moths are the mobile stage. Female moths lay egg masses of 400 to 500 eggs on the undersides of leaves. Different females can pick different trees in the same yard. That’s how several nests end up on separate trees at once, not caterpillars migrating between them. Checking the whole yard, not just the first tree you noticed, is worth doing if more than one host tree is present.
Get a second opinion on what’s happening in your trees
A webbed branch tip in August looks alarming. Most of the time, it’s a problem you can prune your way out of before the nest gets any bigger. Topeka Tree Pro connects homeowners across Shawnee, Jefferson, Jackson, Osage, and Wabaunsee counties, including Topeka itself, with experienced, insured local crews. They can look at what’s actually going on in the canopy. If pruning the nests yourself isn’t realistic, or you’d rather have someone confirm what you’re looking at first, call (785) 333-4052. A crew will get matched to your yard.