Kansas State University


Extension Entomology

Tag: August

Fall Webworm

— by Dr. Raymond Cloyd

The fall webworm (Hyphantria cunea) is prevalent throughout Kansas with webs noticeable on certain trees and shrubs, which is the start of the second generation. Fall webworm nests are typically quite evident in August and September, with silk webbing enclosing the ends of branches and associated foliage or leaves (Figures 1 and 2).

Figure 1. Fall webworm nest on birch tree (Raymond Cloyd)

Fig 1: Fall webworm nest on birch tree by Raymond Cloyd.

Fall webworm larvae (=caterpillars) are pale-green to yellow to nearly whitish in color with black spots (two per each abdominal segment).

Figure 2. Fall webworm nest and accompanying feeding damage (Raymond Cloyd)

Fig 2: Fall webworm nest and accompanying feeding damage (Raymond Cloyd)

The caterpillars are covered with long, white hairs (Figure 3). They feed on a wide range of trees, including: birch, crabapple, maples, hickory, pecan, and walnut. Fall webworm caterpillars, unlike eastern tent caterpillars, remain within the enclosed webbing and do not venture out to feed. Caterpillars consume leaves, resulting in naked branches with dirty webbing attached that contains fecal deposits (“caterpillar poop”). Although feeding by fall webworm caterpillars may ruin the aesthetic appeal of infested trees; the subsequent damage is usually not directly harmful to tree health because trees are primarily allocating resources for storage instead of producing new vegetative growth. The most effective means of dealing with fall webworm infestations is to simply prune-out the webs that enclose the caterpillars. Insecticide sprays may not be effective because the caterpillars remain in the webbing while feeding; thus reducing exposure to spray residues. If insecticides are too be used then be sure to use high-volume spray applications that penetrate the protective webbing or use a rake to disrupt or open-up the webbing so that the insecticide spray contacts the caterpillars.

I need to acknowledge Jeff Otto of Wichita, KS for bringing to my attention that fall webworm was active.

Figure 3. Close-up of fall webworm caterpillar (Raymond Cloyd)



Fig 3. Close-up of fall webworm caterpillar (Raymond Cloyd)


Green June Beetles: Out-and-About

— by Dr. Raymond Cloyd

Green June beetle (Cotinis nitida) adults are actively flying around and “bumping” into people and objects. Adults are 3/4 to 1.0 inches in length, and velvety-green, tinged with yellow-brown coloration (Figure 1).

Fig 1: Close-up of adult green June beetle.

Green stripes with yellow-orange margins extend lengthwise on the front wings. The underside of the body is distinctly shiny and metallic green or gold. Adults fly like “dive bombers” over turfgrass for several weeks in mid-summer. The green June beetle has a one-year life cycle, and overwinters as a mature larva (grub). Adults emerge in late-June and are active during the day, resting at night on plants or in thatch. The adults produce a sound that resembles that of bumble bees.  Adults will feed on ripening fruits (Figure 2) and may occasionally feed on plant leaves.

Fig 2: Adult green June beetle feeding on fruit.
Fig 2: Adult green June beetle feeding on fruit.

The male beetles swarm in the morning, “dive bombing” to-and-fro above the turfgrass searching for females that are located in the turfgrass (they are desperately seeking a mate. Females emit a pheromone that attracts males. Eventually, clusters of beetles will be present on the surface of the soil or turfgrass with several males attempting to mate with a single female (I think this qualifies as an “insect orgy.” Mated females that have survived the experience lay a cluster of 10 to 30 eggs into moist soil that contains an abundance of organic matter. Eggs hatch in about 2 weeks in early August and the young larvae feed near the soil surface. The larvae feed primarily on organic matter including thatch and grass-clippings; preferring soils that are excessive moist. Larvae are 3/8 (early instars) to 1.5 (later instars) inches in length, and exhibit a strange behavioral trait—they crawl on their back (Figure 3) because that they have a constant itch.

Fig 3: Larva (grub) of green June beetle crawling on its back.
Fig 3: Larva (grub) of green June beetle crawling on its back.