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Extension Entomology

Category: Horticulture

Green June Beetle Larvae

–by Dr. Raymond Cloyd

We have received numerous inquiries regarding large grubs (larvae) crawling on their backs across pavements or other hard surfaces. Well, these are the larval stage of the green June beetle, Cotinis nitida. Larvae are 3/8 (early instars) to 1-1/2 (later instars) inches long, and exhibit a strange behavioral trait—they crawl on their back (Figures 1 and 2)—likely due to having a constant itch J. This behavior of crawling on their back is unique among turfgrass-infesting larvae.

 

 

Fig 1. Green June Beetle Larva (Grub) Crawling On Pavement Surface (Auth–Raymond Cloyd, KSU)

Photo for Fig. 2 not available

 

The larvae are abundant now due to the excessive moisture (rain) we have received. Young larvae are generally located at the interface between the soil and thatch layer feeding primarily on organic matter including thatch and grass-clippings; preferring material with a high moisture content. The larvae can be found in swimming pools, garages, and basements. Green June beetle larvae can tunnel 18 inches into the soil; and even deeper in sandy soils.

 

 

 

 

 

 

Scolia dubia: Parasitoid of the Green June Beetle

–by Dr. Raymond Cloyd

 

We continue to see large “wasps” (not cicada killer wasps) feeding on flowering plants such as goldenrod (Solidago spp.) and wild onion (Allium spp.). This is Scolia dubia, which is a parasitoid of green June beetle (Cotinis nitida) larvae or grubs located in the soil. Since there were so many green June beetle adults flying around this year, there is likely to be high populations of grubs/larvae for the parasitoids to attack.

The parasitoids are approximately 3/4-inches long with purple to black wings. The abdomen has red-brown markings with two conspicuous yellow spots on both sides of the third abdominal segment (Figure 1).

Fig 1. Scolia dubia adult feeding on flower (Auth–Raymond Cloyd, KSU)

The parasitoids can be observed flying in a figure-eight pattern several inches above turfgrass infested with green June beetle larvae. A female enters the burrow of a green June beetle larva, uses her ovipositor (egg-laying device) to paralyze the larva, and then she attaches an egg to the underside of the larva. The larva hatches from an egg and consumes the paralyzed green June beetle larva. The larva overwinters in a cocoon at the bottom of the burrow and then pupates in the spring. Adult parasitoids typically emerge from August through September, and feed on flower nectar. They are likely emerging and present later than usual due to the weather conditions we have experienced this year (lots of rain and cool temperatures). Scolia dubia adults, unlike cicada killer males, are not aggressive and females will only sting when handled.

 

 

New Extension Publication – Oak Leaf Itch Mite

–by Dr. Raymond Cloyd

 

We have a new extension publication available entitled, Oak Leaf Itch Mite

This new extension publication, which is actually an update of a previous extension publication, provides up-to-date information on the biology, bites and symptoms, and prevention associated with the oak leaf itch mite (Pyemotes herfsi). The extension publication is available from the following website:

https://www.bookstore.ksre.ksu.edu/pubs/MF2806.pdf

 

Wheel Bug…A Cool-Looking “Bug!”

–by Dr. Raymond Cloyd

If you have spent any time outdoors lately, you may have noticed a very distinct, grotesque looking insect on trees, shrubs, or near homes. This insect is the wheel bug (Arilus cristatus), which is common, and widely-distributed throughout Kansas and the USA. Wheel bugs, also called assassin bugs, are predators that prey on insect pests. However, the nymphs and adult can inflict a painful bite when handled by humans.

Adult wheel bugs are 1.0 to 1.25 inches long, robust with long legs and antennae, and have a stout beak and large eyes on a narrow head (Figure 1).

Fig 1: Wheel Bug Adults Mating. Male is on top of Female (Auth: Raymond Cloyd, KSU)

They are dark-brown to gray and possess a wheel or crest with 8 to 12 protruding teeth-like structures (tubercles) on the thorax that looks like a cogwheel—similar to the dinosaur—Stegosaurus (Figure 2).

Fig 2: Wheel Bug Adult (Auth: Raymond Cloyd, KSU)

Wheel bugs have two long, slender antennae that are constantly moving or weaving around. Females are typically larger than males. Females lay eggs that resemble miniature brown bottles with white stoppers (Figure 3).

Fig 3: Wheel Bug Eggs on Leaf Underside (Auth: Raymond Cloyd, KSU)

The eggs are laid in clusters of 40 to 200, and are glued together and covered with gummy cement that protects eggs from weather extremes and natural enemies (e.g. parasitoids and predators). The egg clusters are located on leaves, or the trunk or branches of trees or shrubs. The nymphs hatch (eclose) from eggs and are bright red in color with black markings. The nymphs do not have the wheel or crest. The life cycle, from egg to adult, can take 3 to 4 months to complete. Wheel bugs are active day and night, and are very shy, tending to hide on the underside of leaves. The wheel bug has one generation per year and overwinters as eggs.

Wheel bugs are voracious predators feeding on a wide-variety of insects, including caterpillars (Figure 4)

Fig 4: Wheel Bug Adult Preparing to Attach a Caterpillar (Auth: Raymond Cloyd, KSU)

beetles, true bugs, sawflies, and aphids. Unfortunately, wheel bugs will feed on beneficial insects such as ladybird beetles and honey bees. The mouthparts are red-brown in color and resemble a tube or straw that is located underneath the head. The mouthparts extend out when wheel bugs are ready to “stab” prey. Wheel bugs paralyze prey with their saliva, which contains a toxic substance that immobilizes prey within 30 seconds. In addition to feeding on insects, wheel bugs are cannibalistic, and will feed on each other…AWESOME J.

 

Euonymus Scale

–by Dr. Raymond Cloyd

This is the time of year when euonymus scale (Unaspis euonymi) becomes noticeable in landscapes on evergreen euonymus (Euonymus japonica) and Japanese pachysandra (Pachysandra terminalis). Euonymus scale overwinters as a mated female on plant stems. Eggs develop and mature underneath the scale, and then nymphs hatch from eggs over a two to three week period. The newly hatched nymphs (crawlers) migrate along the stem and start feeding near the base of host plants. Nymphs can also infect adjacent plants by being blown around on air currents, resulting in infestations often not being detected until populations are extensive and damage is noticeable—like right now. Leaves eventually become spotted yellow or white. Plants located near structures such as foundations (Figure 1),

Fig 1: Euonymus Scale Infestation on Euonymus Plants Located Near Building (Auth: Raymond Cloyd, KSU

walls or in parking areas are more susceptible to euonymus scale than plants growing in open areas that receive sunlight and air movement. Moreover, the variegated forms of euonymus are more susceptible to euonymus scale than the green forms.

Heavy infestations of euonymus scale can ruin the aesthetic appearance of plants, causing complete defoliation or even plant death. Females are dark brown, flattened, and resemble an oystershell. Males, however, are elongated, ridged, and white in color (Figure 2).

Fig 2: Male & Female Euonymus Scale on Leaf (Auth: Raymond Cloyd, KSU)

Males tend to be located on leaves along leaf veins whereas females reside on the stems. There may be up to three generations per year.

 

Cultural practices such as pruning out heavily infested branches—without ruining the aesthetic quality of the plant—are effective in quickly reducing euonymus scale populations; especially this time of year. Be sure to immediately discard pruned branches away from the area. If feasible, avoid planting Euonymus japonica in landscapes since this species is highly susceptible to euonymus scale. Winged euonymus (Euonymus alata) is less susceptible to euonymus scale, even when adjacent plants are infested. Insecticide applications in May through June (now is too late!), which is when the nymphs are most active, will help alleviate problems with euonymus scale later in the season (like right now!). Insecticides recommended for suppression of euonymus scale populations, primarily targeting the nymphs, include acephate (Orthene); pyrethroid-based insecticides such as bifenthrin (Talstar), cyfluthrin (Tempo), and lambda-cyhalothrin (Scimitar); potassium salts of fatty acids (insecticidal soap); and horticultural (petroleum or mineral-based) and neem (clarified hydrophobic extract of neem oil) oils. Always check plants regularly for the presence of nymphs, which will help time insecticide applications. Three to four applications performed at seven to 10-day intervals may be required; however, this is dependent on the level of the infestation. Euonymus scale is a hard or armored scale, so, in most cases, soil or drench applications of systemic insecticides such as imidacloprid (Merit) are not effective in suppressing euonymus scale populations; however, the systemic insecticide dinotefuran (Safari/Zylam), due to its high-water solubility (39,000 ppm), may provide suppression of euonymus scale populations when applied as a drench to the soil. Dormant oil applications can be conducted in winter to kill the overwintering mated females on stems. However, thorough coverage of all plant parts is important to obtain sufficient mortality.

 

Euonymus scale is susceptible to a multitude of natural enemies (e.g. parasitoids and predators), including: braconid and ichneumonid wasps, ladybird beetles, green lacewings, and minute pirate bugs. However, natural enemies may fail to provide enough mortality (‘killing power’) to significantly impact extensive populations of euonymus scale. Furthermore, insecticides such as acephate (Orthene), and many of the pyrethroid-based insecticides, including bifenthrin (Talstar), cyfluthrin (Tempo), and lambda-cyhalothrin (Scimitar) are very harmful to most natural enemies, so applications of these materials may disrupt any natural regulation or suppression.

 

 

Twospotted Spider Mites

–by Dr. Raymond Cloyd

The recent hot weather we are experiencing throughout Kansas is conducive to the development of the twospotted spider mite, Tetranychus urticae (Figure 1), resulting in extensive feeding damage to the leaves of horticultural plants in gardens and landscapes (Figures 2 and 3). Twospotted spider mite is a warm-weather mite with populations commonly active from late spring through early fall. Summer temperatures allow twospotted spider mite females to reproduce rapidly, which helps to overwhelm natural enemy (e.g. predators) populations by producing multiple generations throughout the season.

Fig 1. Close-up of twospotted spider mite adults.

Fig 2. Twospotted spider mite feeding damage on euonymus bush leaves (Auth–Raymond Cloyd, KSU)

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

The management of twospotted spider mite populations involves maintaining plant health by avoiding ‘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, which will be helpful in minimizing potential problems with twospotted spider mite populations. For instance, inadequate moisture or over fertilizing plants, especially with water-soluble nitrogen-based fertilizers, can enhance development and reproduction of twospotted spider mites.

It is important to monitor for twospotted spider mite populations regularly by shaking plant parts (e.g. leaves, branches, or twigs) onto a clipboard with a white sheet of paper, and then look 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 example, plant-feeding spider mites typically leave a green streak when crushed whereas predatory mites leave a red streak.

A quick and effective method of managing 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 fact, the only “true miticide” still available is hexakis or fenbutatin-oxide, however, this active ingredient cannot be purchased alone as the active ingredient is typically formulated with another pesticide (insecticide) such as acephate (Orthene). However, homeowners can apply commercially available insecticidal soaps (potassium salts of fatty acids) or horticultural oils. Always read the label and apply miticides before twospotted spider mite populations are extensive and causing damage. Moreover, be sure to rotate miticides with different modes of action to avoid twospotted spider mite populations developing resistance. If possible, 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.

 

 

 

“Bugs” To Be On The Look-Out For

–by Dr. Raymond Cloyd

 

Green June Beetles: lots still flying around. This has been one of the best…or worst years…depending on your perspective.

Japanese Beetle Adults: many are feeding on fruit trees and roses.

Bagworms: time is running-out in regards to applying insecticides…you have about two to three more weeks…and then it is too late.

Mosquitoes: with all the rain and moist conditions, mosquitoes (adults) are very prevalent.

Milkweed Aphids: many milkweed plants are literally covered with the milkweed aphid. Simply use a forceful water spray to dislodge them from plants.

Squash Bugs: eggs have hatched and nymphs are looking for suitable feeding sites…on the leaf underside.

 

Mimosa Webworm

–by Dr. Raymond Cloyd

Mimosa webworm (Homadaula anisocentra) larvae (=caterpillars) are now feeding and creating protective habitats on honeylocust (Gleditsia triacanthos) and mimosa (Albizia julibrissin) trees, which are quite noticeable in the Manhattan (KS) area. The larvae (=caterpillars) are 1/2 inch long when fully-grown (Figure 1),

Fig 1. Mimosa Webworm Caterpillars Feeding On Leaves (Auth–Raymond Cloyd, KSU)

Fig 2. Mimosa Webworm Webbing On Branch End (Auth–Raymond Cloyd, KSU)

Webbing commonly starts at the tops of trees and serves to protect caterpillars from natural enemies (parasitoids and predators) and insecticide spray applications. Heavily-infested trees are brown or scorched in appearance (Figure 3) as the caterpillars skeletonize the leaf tissue. Caterpillars eventually fall from trees on a silken strand before pupating. Mimosa webworm pupates in bark crevices or pupae are glued to structures (e.g. buildings).

Fig 3. Mimosa Webworm Feeding Damage (Auth–Raymond Cloyd, KSU)

In regards to controlling mimosa webworm infestations, it is probably too late although initial damage may be minimal. Insecticides that can be used to suppress mimosa webworm populations, in which the caterpillars are exposed, include: acephate (Orthene), Bacillus thuringiensis subsp. kurstaki (Dipel), spinosad (Conserve), and several pyrethroid-based insecticides (e.g. bifenthrin, cyfluthrin, and permethrin). Read the label of each product to ensure that “webworms” are listed. High-volume spray applications are required to contact the caterpillars inside the protective webbing. If trees are already heavily-infested with webbing then it is too late to apply an insecticide. If possible, selective pruning can quickly remove isolated or localized infestations of mimosa webworm.

Green June Beetle Adults

–by Dr. Raymond Cloyd

Green June beetle, Cotinis nitida, adults are actively flying around in massive numbers near managed and/or unmanaged grassy areas, and ‘bumping’ into people and objects. Adults are 3/4 to 1.0 inch long, velvety-green, and tinged with yellow-brown coloration (Figure 1). 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 resemble ‘dive bombers’ flying around for several weeks in July. Green June beetle adults are sometimes confused with Japanese beetle (Popilla japonica) adults—but they really do not look alike (Figures 2 and 3).

Fig 1. Green June Beetle Adult (Auth–Raymond Cloyd, KSU)

Fig 2. Green June Beetle Adult (Auth–Raymond Cloyd, KSU)

Fig 3. Japanese Beetle Adult (Auth–Raymond Cloyd, KSU)

Green June beetle has a one-year life cycle, and overwinters as a mature larva or grub. Adults generally emerge in late-June and are active during the day, resting at night on plants, in thatch, or in compost. Adults produce a sound similar to that of bumble bees. Adults will feed on ripening fruits and corn tassels, and may occasionally feed on plant leaves. Male beetles swarm in the morning, ‘dive bombing’ to-and-fro just above managed and/or unmanaged grassy areas where females are located. Females emit a pheromone that attracts the males. Clusters of beetles may be seen on the surface of the soil or in grassy areas with several males attempting to mate with a single female, resulting in an ‘insect orgy.’

Mated females that survive the ‘experience’ will lay clusters of 10 to 30 eggs in moist soil containing a high amount of organic matter. Eggs hatch in about two weeks, in early August, and young larvae feed near the soil surface. The larvae feed primarily on organic matter including thatch and grass-clippings; preferring material with a high moisture content. Larvae are 3/8 (early instars) to 1.5 (later instars) inches long, and exhibit a strange behavioral trait—they crawl on their back—likely due having a constant itch.

 

 

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