Kansas State University

— by Dr. Raymond Cloyd

It is time to be aware of the presence of pine tortoise scale, Toumeyella parvicornis, on pine trees. We have already received samples of pine tortoise scale with the crawlers (nymphs) emerging from the eggs. Pine tortoise scale feeds on many different types of pines, including: Scots, Austrian, and red. Immature females are round, brown, and wrinkled in appearance (Figure 1),

Fig 1. Pine tortoise scale on branch of pine tree (Author–Raymond Cloyd, KSU)

and overwinter on twigs (Figure 2).

Fig 2. Pine tortoise scale females on the twig of a pine tree (Author–Raymond Cloyd, KSU)

Eggs are laid underneath the body of adult females. In general, eggs hatch into red crawlers (nymphs) from May (RIGHT NOW) through June (Figure 3).

Fig 3. Pine tortoise scale crawlers emerging from eggs of females (Author–Raymond Cloyd, KSU)

The crawlers eventually find suitable locations and start feeding. Crawlers can spread to other pines via wind currents or by attaching to birds. Females can produce up to 500 crawlers within a generation. Males, like most scale species, develop into winged individuals that fly and mate with females. Males do not feed and eventually die. In Kansas, there is typically one generation of pine tortoise scale per year.

Pine tortoise scale feeding results in yellowing of needles, stunted needle growth, and under extensive populations can result in death of pines. Young pine trees, in general, are more susceptible to pine tortoise scale than older (mature) trees. In addition, foliage closer to the ground tends to support higher populations of pine tortoise scale than foliage higher in the tree canopy. Pine tortoise scale also produces copious amounts of honeydew, a clear sticky liquid that serves as a growing medium for black sooty mold. Entire pine trees may appear black from black sooty mold under heavy infestations of pine tortoise scale.

A forceful water spray applied twice per week will quickly dislodge/remove the crawlers and mature females from infested pine trees. Insecticides that are useful in suppressing populations of pine tortoise scale crawlers include: acephate (Orthene), acetamiprid (TriStar), bifenthrin (Talstar), cyfluthrin (Tempo), dinotefuran (Safari), imidacloprid (Merit), insecticidal soap (potassium salts of fatty acids), and horticultural oils (petroleum, mineral or neem-based). These insecticides must be applied when crawlers are active…which is RIGHT NOW…in order to obtain maximum suppression of pine tortoise scale populations and alleviate future problems.

— by Dr. Raymond Cloyd

We have received notice from Jeff Otto (Wichita, KS) that bagworms, Thyridopteryx ephemeraeformis, are emerging from eggs, and the young caterpillars are out-and-about feeding on plants. Eventually bagworms will be present throughout the rest of Kansas feeding on both broadleaf and evergreen trees and shrubs. Therefore, now is the time to initiate action against this insect pest. Bagworms are primarily a pest of conifers but have expanded their host range to include a number of broadleaf plants, such as; rose, honeylocust, and flowering plum. Hand-picking small caterpillars (along with their accompanying bag) and placing them into a container of soapy water will kill them directly. This practice, if feasible, will quickly remove populations before they can cause substantial plant damage.

For those not really interested in enjoying the nice hot weather and hand-picking, a number of insecticides are labeled for use against bagworms including those with the following active ingredients (trade name 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 that are feeding aggressively on plant foliage (Figure 1).

Fig 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. Furthermore, females feed less as they prepare for reproduction, which reduces their susceptibility to spray applications and any residues. The bacterium Bacillus thuringiensis subsp. kurstaki (Figure 2) is active on young caterpillars but the active ingredient must be consumed or ingested to be effective.

Fig 2. Product (Dipel) containing Bacillus thuringiensis subsp. kurstaki as the active ingredient (Author–Raymond Cloyd, KSU)

Therefore, thorough coverage of all plant parts and frequent applications are required. The insecticide is sensitive to ultra-violet light degradation and rainfall, which reduces residual activity. 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);

Fig 3. Product (Captain Jack’s Deadbug Brew) containing spinosad as the active ingredient (Author–Raymond Cloyd, KSU)

and Monterey Garden Insect Spray. The insecticide works by contact and ingestion (stomach poison); however, activity is greatest when ingested. Products containing spinosad can be used against older or larger bagworm caterpillars later on in the season. Cyfluthrin, lambda-cyhalothrin, trichlorfon, chlorantraniliprole, and indoxacarb can be used against both the young and the older caterpillars. However, thorough coverage of all plant parts, especially the tops of trees and shrubs, 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 (Figure 4).

Fig 4. Dead Arborvitae shrub as a result of extensive bagworm feeding (Author–Raymond Cloyd, KSU)

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.

I want to acknowledge Jeff Otto as he has been very helpful in providing me information on the activity of insect and mite pests in south-central KS. If anyone is interested in helping me determine insect and mite pest activity throughout the growing season in KS please let me know.