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Extension Entomology

Category: Lawn and Garden

Twospotted Spider Mites

Posted on by Sharon Schroll

— by Dr. Raymond Cloyd

The extreme heat and lack of moisture we are experiencing throughout most of Kansas is conducive to the development of the twospotted spider mite, Tetranychus urticae (Figure 1),

Figure 1. Close-up of twospotted spider mite adult (Author–Raymond Cloyd, KSU)

horticultural plants in gardens and landscapes (Figures 2 and 3).

Figure 2. Twospotted spider mite feeding damage on clematis leaf (Author–Raymond Cloyd, KSU)

Figure 3. Twospotted spider mite feeding damage on tomato leaves (Author–Raymond Cloyd, KSU)

Twospotted spider mite is a warm-weather mite with populations typically active from late spring through early fall. Summer temperatures allow by producing multiple generations throughout the season.

The management of twospotted spider mite populations involves maintaining plant health in order to avoid ‘stress,’ implementing sanitation practices, and/or using pesticides with miticidal activity (miticides/acaricides). First, prevent plants from experiencing moisture ‘stress’ by maintaining proper watering and mulching practices to reduce potential problems with twospotted spider mite populations. For example, inadequate moisture or overfertilizing plants, particularly with nitrogen-based fertilizers, can enhance development and reproduction of twospotted spider mites. Furthermore, be sure to monitor for twospotted spider mite populations regularly by shaking branches or twigs onto a clipboard with a white sheet of paper, and looking for the mites crawling around (you can actually see the mites). You can crush the mites on the white sheet of paper to determine if they are a pest or not. For instance, plant-feeding spider mites typically leave a green streak when crushed whereas predatory mites leave a red streak. A quick and effective method of dealing with twospotted spider mite populations is applying a forceful water spray throughout the plant canopy at least twice per week during the season. Forceful water sprays will dislodge eggs and the motile life stages (larvae, nymphs, and adults). Be sure to direct forceful water sprays toward the leaf undersides where all life stages (eggs, nymphs, larvae, and adults) of the twospotted spider mite are located. The removal of plant debris and weeds eliminates alternative hosts and overwintering sites.

There are a number of pesticides with miticidal activity available to professionals for suppression of twospotted spider mite populations outdoors, including: abamectin (Avid), acequinocyl (Shuttle), bifenazate (Floramite), etoxazole (TetraSan), hexythiazox (Hexygon), potassium salts of fatty acids (M-Pede), and horticultural oils (petroleum, mineral, or neem-based). Homeowners do not have as many options in regards to miticides. The only “true miticide” still available is hexakis or fenbutatin-oxide, however, this active ingredient cannot be purchased by itself as the active ingredient is usually formulated with acephate (Orthene). However, homeowners can apply commercially available insecticidal soaps (potassium salts of fatty acids) and horticultural oils. Always read the label and apply miticides before twospotted spider mite populations are extensive and causing damage. Furthermore, be sure to rotate miticides with different modes of action to avoid twospotted spider mite populations developing resistance. If possible, try to target ‘hot spots’ or localized infestations of twospotted spider mites, which will reduce the potential for resistance developing. Be sure to thoroughly cover all plant parts with spray applications; especially when using pesticides with contact activity. Some miticides such as abamectin (Avid) and etoxazole (TetraSan) have translaminar activity, which means the material penetrates into leaf tissues and forms a reservoir of active ingredient within the leaf. This provides residual activity even after spray residues have dried. Mites that feed on leaves will ingest a lethal concentration of the active ingredient and be killed.

It is important to note that many pesticides used to suppress other insect pests encountered on plants in landscapes and gardens may be harmful to the natural enemies of twospotted spider mite; consequently, resulting in an inadvertent increase in twospotted spider mite populations or secondary pest outbreaks.

 

Fall Webworm

Posted on by Sharon Schroll

–by Dr Raymond Cloyd

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

Figure 1. Fall webworm nest on birch tree (Author–Raymond Cloyd, KSU)

 

Figure 2. Fall webworm nest on walnut tree (Author–Raymond Cloyd, KSU)

Fall webworm larvae or caterpillars are pale-green to yellow to nearly whitish with black spots (two per each abdominal segment). Caterpillars are covered with long, white hairs (Figure 3).

Figure 3. Close-up of fall webworm larvae (Author–Raymond Cloyd, KSU)

They feed on a wide range of trees, including: birch, crabapple, maples, hickory, pecan, mulberry, 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 webbing attached that contains fecal deposits or ‘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, especially larger trees because larger trees are primarily allocating resources for storage with less being allocated to producing new vegetative growth. However, smaller trees infested with fall webworm may look awful (Figure 4).

Figure 4. Young tree heavily-infested with fall webworm (Author–Raymond Cloyd, KSU)

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 used 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.

 

Pine Tortoise Scale

Posted on by Sharon Schroll

— 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.

Bagworms: They Have Arrived….and Not From Outer Space!

Posted on by Sharon Schroll

— 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.

Ash/Lilac Borer

Posted on by Sharon Schroll

–by Raymond Cloyd

It is that time year to be aware of and prevent damage from the ash/lilac borer (Podosesia syringae). Ash/lilac borer adults are generally active from late-April through June, although the extended cool period we experienced in April more than likely shifted initial activity into early to mid-May. Adults are brown, clearwing moths that resemble paper wasps (Figure 1). Adult females lay tan, oval-shaped eggs in cracks and crevices, or wounds at the base of plant stems. A single female can live about one week and lay up to 400 eggs. Below are nine items related to the life history parameters and management strategies associated with the ash/lilac borer:

Fig 1. AshLilac Borer Adult (Author–City of Edmonton)

 

  1. The larvae cause plant damage by creating tunnels and feeding within the bark (cambium). In addition, larvae can tunnel further into the wood and feed within the sapwood and heartwood.

 

  1. Larval feeding restricts the flow of water and nutrients resulting in shoot or branch dieback. Ash/lilac borer feeds primarily at the base of plant stems creating swollen areas or cracks, and where major branches attach to the trunk.

 

  1. Evidence of larval feeding includes the presence of light-colored sawdust (frass) that accumulates at the base of infected trees or shrubs (Figure 2).

Fig 2. Sawdust Located At The Base Of An Infected Tree (Author–Raymond Cloyd, KS)

 

  1. Ash/lilac borer overwinters as a late-instar larva located in feeding tunnels or galleries.

 

  1. Trees or shrubs that have been infested with ash/lilac borers will have brown papery pupal cases protruding from the bark (Figure 3). These are where the adults emerged from.

 

Fig 3. Pupal Cases Of AshLilac Borer Protruding From Tree Trunk (Author–Raymond Cloyd, KSU

 

 

  1. The best way to minimize problems with ash/lilac borer is to avoid ‘plant stress’ by providing proper cultural practices, such as; irrigation (watering), fertilization, pruning, and mulching. Stressed plants, in general, are more susceptible to attack than so called ‘healthy plants.’ A two to three foot wide mulched area around the base of trees and shrubs prevents injury from lawn mowers and weed-trimmers, which can girdle trees and shrubs thus leading to ‘stress.’ Furthermore, avoid pruning plants in late spring through early summer (under usual weather conditions) as this is when adults are typically present and the volatiles emitted from pruning cuts may attract adult females.

 

  1. Insecticides containing the active ingredients, permethrin or bifenthrin can be applied to the bark, at least up to six feet from the base, in order to prevent ash/lilac borer larvae from entering plants after eggs hatch. Ash/lilac borer larvae crawl on the bark searching for entry points, which exposes them to insecticide residues.
  2. Pheromone traps are commercially available that capture adult males (Figure 4), which helps to estimate when females will be laying eggs. Pheromone traps help in timing insecticide applications. Insecticide spray applications should begin 7 to 10 days after capturing the first adults. Be sure to also check pheromone traps two to three times per week and record the number of newly captured adult males.

Fig 4. Pheromone Trap Used To Capture AshLilac Borer Adult Males (Author–Raymond Cloyd, KSU)

For more information regarding ash/lilac borer management contact your county or state extension specialist.

 

 

 

 

 

 

Cross-Striped Cabbageworm

Posted on by Sharon Schroll

–by Dr. Raymond Cloyd

We have received inquiries regarding caterpillars feeding, and completely devouring cole crops, including: collards, Brussel sprouts, kohlrabi, turnip, and kale (Figures 1 through 3).

 

Figure 1. Cross-Striped Cabbageworms Feeding (Author–Raymond Cloyd, KSU, Department of Entomology)

Figure 2. Damage Caused By Cross-Striped Cabbageworm (Author–Raymond Cloyd, KSU, Department of Entomology)

Figure 3. Cross-Striped Cabbageworm Larvae Feeding (Author–Raymond Cloyd, KSU, Department of Entomology)

These are the cross-striped cabbageworm (Evergestis rimosalis). The caterpillars have black and white striping on the back, two dots on each abdominal segment, and yellow lines that extend the length of the body on both sides (Figures 4 and 5).

Figure 4. Cross-Striped Cabbageworm (Author–Raymond Cloyd, KSU, Department of Entomology)

Figure 5. Cross-Striped Cabbageworm (Author–Scott Eckert, Harvey County Extension, Newton, KS)

 

They are not a common insect pest but this year they have been a problem on many cole crops. The cross-striped cabbageworm may be found feeding along with the imported cabbageworm (Artogeia rapae) (Figure 6).

Figure 6. Cross-Striped Cabbageworm and Imported Cabbageworm Larvae (Author–Raymond Cloyd, KSU, Department of Entomology)

There is really no justification for applying an insecticide once plants have been heavily-damaged. Therefore, the best option is to hand-pick cross-striped cabbageworm caterpillars and place into a container of soapy water.

Look At All the Painted Ladies

Posted on by Sharon Schroll

–by Dr. Raymond Cloyd

This year, throughout Kansas, we have seen an abundance and wonderful display of painted lady (Vanessa cardui) butterflies. The painted lady butterfly is one of the most common and widely distributed butterflies worldwide. Adults are distinct [and very different looking than the monarch butterfly (Danaus plexippus)] having wings that are mottled brown-yellow, white, brown, and black. There is a row of “small” eyespots on the underside of the hindwings (Figure 1).

Figure 1. Painted Lady Butterfly Adult (Author–Raymond A. Cloyd)

In addition, there is a white crescent on the front edge of the forewing (Figure 2).

 

Figure 2. Painted Lady Butterfly Adult (Author–Raymond A. Cloyd)

 

 

Painted lady adults feed on the nectar of many different plants in flower including sage (Salvia spp.), stonecrop (Sedum spp.) (Figures 3 and 4), butterfly bush (Buddleia spp.), and coneflower (Echinacea spp.).

 

Figure 3. Painted Lady Butterfly Adults Feeding On Stonecrop (Sedum spp.) Flowers (Author–Raymond A. Cloyd)

Figure 4. Painted Lady Butterfly Adults Feeding On Flowers Of Stonecrop (Sedum spp.) (Author–Raymond A. Cloyd).

 

The larvae are spiny and feed on the leaves of various plants including sunflower (Helianthus spp.), hollyhock (Alcea rosea), burdock (Arctium spp.), and thistle (Cirsium or Carduus spp.). The painted lady overwinters as an adult; however, most die during the winter (if we have a so-called winter). The painted lady adults migrate northward from the southwest from March through November with two flight periods. In fact, painted lady adults can fly >600 miles. It is possible that the front associated with Hurricane Harvey this year may have “pushed” more adults northward into Kansas. However, this is not the first time Kansas has experienced a plethora of painted lady butterflies. For instance, a migration flight in 1983 was so extensive that butterflies hitting windshields were a hazard to motorists. In addition, a single northward migration contained approximately 3 billion painted lady butterflies. So, just enjoy a wonder of nature…lots of painted lady butterflies.

Japanese Beetles Are Back!

Posted on by Sharon Schroll

–by Dr. Raymond Cloyd

Japanese beetle adults are out in full-force in certain regions of Kansas feeding on different plant species, but especially roses (Rosa spp.). The means of dealing with the adult stage of Japanese beetle are limited, and have been for many years, with the use of insecticides still being the primary plant protection strategy. Japanese beetle, Popillia japonica is native to Japan and was first reported in the United States in 1916 in the state of New Jersey. Currently, Japanese beetles are established from Maine to Georgia and in nearly every state east of the Mississippi River and several mid-western states.

Figure 1. Japanese beetle adult (Author-Raymond Cloyd, KSU)

Japanese beetles are established in eastern and central portions of Kansas, and are slowly moving westward. Japanese beetle adults are one of the most destructive insect pests of horticultural plants in both landscapes and gardens. The larvae or grub is a major turfgrass insect pest in home lawns, commercial settings, and golf courses.

Japanese beetle adults are 9/16 of an inch in length and metallic green with coppery-brown wing covers (Figure 1). There are about 14 tufts of white hair present along the end of the abdomen (Figure 2). Adult Japanese beetles emerge from the soil and live from 30 to 45 days feeding on plants over a four-to-six-week period.

Figure 2. Japanese beetle adult. Note tufts of white hair on the end of the abdomen (Author-Raymond Cloyd, KSU)

Adults feed on many ornamental plants including: trees, shrubs, vines, herbaceous annual and perennials, and of course—roses. Plant placement in the landscape and volatiles emitted by plants are factors that can influence adult acceptance. Moreover, Japanese beetle adults produce aggregation pheromones that attract individuals (both males and females) to the same feeding location. Adults can fly up to five miles to locate a feeding site; however, they tend to fly only short distances to feed and lay eggs.

Japanese beetle adults feed through the upper leaf surface (epidermis) and leaf center (mesophyll), leaving the lower epidermis intact. Adults usually avoid feeding on tissue between leaf veins, resulting in leaves appearing lace-like or skeletonized (Figure 3).

Figure 3. Lace-like or skeletonized damage to leaf caused by Japanese beetle adult feeding (Author-Raymond Cloyd, KSU)

They are most active during warm days, feeding on plants exposed to full sun throughout the day, which is likely why roses are a susceptible host plant because roses require at least six hours of direct sunlight in order to flower. Japanese beetle adults start feeding at the top of plants, migrating downward after depleting food sources. Japanese beetle adults aggregate in masses on rose flowers (Figure 4). Although adult beetles feed mainly on flowers, they will also feed on leaves (Figure 5). Adults chew holes in flower buds;

Figure 4. Japanese beetle adults aggregating on rose flower (Author-Raymond Cloyd, KSU)

 

 

Figure 5. Japanese beetle adults feeding on linden (Tilia spp.) leaf (Author-Raymond Cloyd, KSU)

preventing flowers from opening or causing petals to fall prematurely. Furthermore, adults will consume entire rose petals, and feed on the pollen of fully-opened flowers.

Japanese beetle adult management involves implementing a variety of plant protection strategies, including: cultural, physical, and insecticidal. Cultural is associated with maintaining healthy roses through proper irrigation, fertility, mulching, and pruning, which are important in minimizing “stress, which may possibly decrease susceptibility. In addition, removing weeds such as smartweed (Polygonum spp.) that are attractive to Japanese beetle adults may alleviate infestations. Physical involves hand-picking or collecting Japanese beetle adults from roses before populations are extensive. The best time to hand-pick or collect adults is in the morning when ambient air temperatures are typically “cooler.” Adults can be easily collected by placing a wide-mouthed jar or bucket containing rubbing alcohol (70% isopropyl alcohol) or soapy water underneath each adult, and then touching them. Adults that are disturbed fold their legs perpendicular to the body, and fall into the liquid and are subsequently killed. This procedure, when conducted daily or every-other-day, particularly after adults emerge, may substantially reduce plant damage. The use of Japanese beetle traps (Figure 6)

Figure 6. Japanese beetle trap (Author-Raymond Cloyd, KSU)

 

is not recommended since the floral lure and synthetically-derived sex pheromone (Figure 7) may attract more adults into an area than would “normally” occur. Japanese beetle adults may also feed on roses before reaching the traps, which increases potential damage.

Figure 7. Floral lure (on left) and sex pheromone (on right) associated with Japanese beetle trap (Author-Raymond Cloyd, KSU) (PICTURE NOT SHOWN)

 

Spray applications of contact insecticides will kill Japanese beetle adults. However, repeat applications will be required; especially when populations are excessive. In addition, thorough coverage of all plant parts will increase effectiveness of the application. The insecticide carbaryl (Sevin®) and several pyrethroid-based insecticides including those containing bifenthrin or cyfluthrin as the active ingredient can be used to suppress Japanese beetle adult populations. However, most of these insecticides also directly harm many natural enemies (parasitoids and predators) so their continual use may lead to secondary pest outbreaks of other pests including the twospotted spider mite (Tetranychus urticae). Furthermore, these insecticides are directly harmful to honey bees and bumble bees. Therefore, applications should be conducted in the early morning or late evening when bees are less active. In general, systemic insecticides, are not effective because Japanese beetle adults have to feed on leaves and consume lethal concentrations of the active ingredient. If extensive populations are present, then damage to plants may still occur.

The battle against Japanese beetle adults requires patience, persistence, and diligence in order to prevent adults from causing substantial damage to roses and other susceptible plants.

 

Bagworms are Here!

Posted on by Sharon Schroll

–by Dr. Raymond Cloyd

Bagworms are Here!

Now is the time to start taking action against that “infamous” insect pest known as the bagworm (Thyridopteryx ephemeraeformis). Throughout Kansas, bagworm eggs have hatched and the young caterpillars are feeding on both broadleaf and evergreen trees and shrubs. Bagworms are primarily a pest of conifers but have expanded their host range to include a number of broadleaf plants, including: 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 interested in 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/Thuricide), cyfluthrin (Tempo), lambda-cyhalothrin (Scimitar), trichlorfon (Dylox), indoxacarb (Provaunt), chlorantraniliprole (Acelepryn), and spinosad (Conserve). Many of these active ingredients are commercially available and sold under different trade names or as generic products. However, several insecticides may not be directly available to homeowners. The key to managing bagworms with insecticides is to apply early and frequently enough in order to kill the highly susceptible young caterpillars that are feeding aggressively on plant foliage (Figure 1). Older caterpillars that develop

 

Figure 1. Young Bagworm Feeding On Conifer (Author-Raymond Cloyd, Kansas State University)

 

later in the season (Figure 2) 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 is active on young caterpillars; however, the active ingredient must be consumed to be effective, so thorough coverage of all plant parts and frequent applications are required. This compound 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; and Monterey Garden Insect Spray. These products work by contact and ingestion (stomach poison) although they are most

 

Figure 2. Older Bagworms (Author-Raymond Cloyd, Kansas State University)

 

 

effective when ingested and can be used against older or larger bagworm caterpillars (Figure 3). Cyfluthrin, lambda-cyhalothrin, trichlorfon, chlorantraniliprole, and indoxacarb may 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 initiate feeding, and frequent applications are required. The reason multiple applications are needed when bagworms are first detected is because young bagworms “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 may actually kill plants, especially newly transplanted small evergreens, since evergreens do not usually produce another flush of growth.

 

Figure 3. Captain Jack’s DeadBug Brew (Author-Raymond Cloyd, Kansas State University)

If you have any questions regarding the management bagworms contact your county horticultural agent, or university-based or state extension entomologist.