Kansas State University

–by Dr. Raymond Cloyd

For those of you that have been waiting patiently or for some…impatiently; it is time to ‘get ready’ to spray for bagworms. In due time, bagworms will be present throughout Kansas feeding on broadleaf and evergreen trees and shrubs. Therefore, now is the time to initiate action against bagworms once they are observed on plants. Bagworms are primarily a pest of conifers; however, they have expanded their host range to include a number of broadleaf plants, such as; rose, honey locust, and flowering plum. It is important to apply insecticides when bagworms are small to maximize effectiveness and subsequently reduce plant damage.

A number of insecticides are labeled for use against bagworms including those with the following active ingredients (common trade names are in parentheses): acephate (Orthene), Bacillus thuringiensis subsp. kurstaki (Dipel), cyfluthrin (Tempo), lambda-cyhalothrin (Scimitar), trichlorfon (Dylox), indoxacarb (Provaunt), chlorantraniliprole (Acelepryn), and spinosad (Conserve). Most of these active ingredients are commercially available and sold under various trade names or as generic products. Several insecticides, however, may not be directly available to homeowners.

The key to managing bagworms with insecticides is to apply early and frequently enough to kill the highly susceptible young caterpillars feeding on plant foliage (Figure 1).

Figure 1. Young bagworm larvae or caterpillar feeding on conifer (Author–Raymond Cloyd, KSU)

Older caterpillars that develop later in the season are typically more difficult to kill with insecticides. Moreover, females feed less as they prepare for reproduction, which reduces their susceptibility to spray applications and any residues. The bacterium, Bacillus thuringiensis subsp. kurstaki, which is sold under various trade names (Figure 2

Figure 2. Product (Thuricide) containing Bacillus thuringiensis subsp. kurstaki as the active ingredient (Author–Raymond Cloyd, KS)

), is only active on young caterpillars and must be consumed or ingested to be effective. Therefore, thorough coverage of all plant parts and frequent applications are required. The insecticide is sensitive to ultra-violet light degradation and rainfall, which can reduce residual activity (persistence). Spinosad is the active ingredient in a number of homeowner products, including: Borer, Bagworm, Tent Caterpillar, and Leafminer Spray; Captain Jack’s DeadBug Brew (Figure 3);

Figure 3. Product containing spinosad as the active ingredient (Author–Raymond Cloyd, KSU)

and Monterey Garden Insect Spray. The insecticide works by contact and ingestion; however, activity is greatest when ingested by bagworms. Last year (2018), I made weekly applications for four-weeks in June and killed nearly 100% of the bagworms on my arborvitae and juniper shrubs. Consequently, the plants looked aesthetically pleasing during the season.

Cyfluthrin, lambda-cyhalothrin, trichlorfon, chlorantraniliprole, and indoxacarb can be used against where bagworms commonly start feeding, and frequent applications are essential in achieving sufficient suppression of bagworm populations. The reason multiple applications are needed is that bagworm eggs do not hatch simultaneously but hatch over a certain period of time depending on temperature, and young bagworms can ‘blow in’ (called ‘ballooning’) from neighboring plants on silken threads. If left unchecked, bagworms can cause significant damage and ruin the aesthetic quality of plants. In addition, bagworms can actually kill plants, especially newly transplanted small evergreens, since evergreens do not usually produce another flush of growth after being fed upon or defoliated by bagworms

If you have any questions on how to deal with bagworms in your garden or landscape contact your county horticultural agent, or university-based or state extension entomologist.

–by Dr. Raymond Cloyd

Hordes of goldenrod soldier beetle, Chauliognathus pennsylvanicus, adults are now feeding on goldenrod (Solidago spp.) (Figure 1) and other flowering plants. Adults are extremely abundant feeding on the flowers of wild onion (Allium spp.) (Figure 2), and can also be seen feeding on linden trees (Tilia spp.) in bloom. Adults, in fact, can be seen feeding and mating simultaneously. The goldenrod soldier beetle is common to the western and eastern portions of Kansas.

Fig 1. Goldenrod Soldier Beetle Adults Feeding On Goldenrod Flowers (A.–Raymond Cloyd, KSU)

Fig 2. Goldenrod Soldier Beetle Adults Feeding on Wild Onion Flowers (A.–Raymond Cloyd, KSU)

Adults are about 1/2 inch (12 mm) long, elongated, and orange with two dark bands located on the base of the forewings (elytra) and thorax (middle section) (Figure 3). Adults are usually present from August through September. Adult soldier beetles feed on the pollen and nectar of flowers; however, they are also predators, and will consume small insects such as aphids and caterpillars. Flowers are a great place for the male and female soldier beetle adults to meet, get acquainted, and mate (there is no wasting time in the insect world J) (Figure 4). Soldier beetle adults do not cause plant damage. Sometimes adults will enter homes but they are rarely a concern. The best way to deal with adults in the home is to sweep, hand-pick, or vacuum.

Fig 3. Goldenrod Soldier Beetle Adult (Author–Raymond Cloyd, KSU).

Fig 4. Goldenrod Soldier Beetle Adults Mating (A.–Raymond Cloyd, KSU)

Adult females lay clusters of eggs in the soil. Each egg hatches into a larva that is dark-colored, slender, and covered with small dense hairs or bristles, which gives the larva a velvety appearance. The larva resides in soil feeding on grasshopper eggs. Occasionally, the larva will emerge from the soil to feed on soft-bodied insects and small caterpillars.

–by Dr. Raymond Cloyd

Have you seen large wasp-like looking insects feeding on flowering plants such as wild onion, Allium spp and goldenrod, Solidago spp.? Well, this is Scolia dubia, which is a parasitoid of green June beetle, Cotinus nitida, larvae (grubs) located in the soil. Parasitoids are approximately 3/4-inches long with purple to black wings. The abdomen has red-brown markings and two very conspicuous yellow spots on both sides of the third abdominal segment (Figure 1). The parasitoids may be seen flying in a figure-eight pattern several inches above turfgrass infested with green June beetle larvae. The parasitoid can be seen feeding on goldenrod flowers along with goldenrod soldier beetle, Chauliognathus pennsylvanicus, adults (Figure 2) (see next article).

Fig 1. Adult Scolia dubia Feeding on Wild Onion Flower (Author–Raymond Cloyd, KSU).

Fig 2. Scolia dubia Adult Feeding on Goldenrod Flowers Along with Goldenrod Soldier Beetle Adults (A.–Raymond Cloyd, KSU)

Female parasitoids enter the burrow of a green June beetle larva, paralyze the larva by stinging it, and then attach an egg to the underside of the larva. After hatching, the parasitoid larva consumes the dead green June beetle larva. Scolia dubia overwinter as a pupa in a cocoon located at the bottom of the burrow and then emerge (eclose) later as an adult. Adult parasitoids typically emerge (eclose) in middle to late August and feed on flower pollen and nectar. These parasitoids, unlike cicada killer wasps, are not very aggressive and will only sting (at least the females) when handled or stepped on with bare feet.