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Extension Entomology

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Japanese Beetles Are Back!

–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.

 

LACE BUGS: NOTHING TO WORRY ABOUT?

–by Dr. Raymond Cloyd

Lace bugs are insects that are present throughout Kansas feeding on a variety of plant types; however, lace bugs are not really a major insect pest of garden and landscape plants because they typically do not inflict significant direct harm to plants. Nonetheless, abundant populations may reduce the aesthetic appearance of certain plant types. Lace bugs feed on a wide-range of trees and shrubs, including: azalea, basswood, cotoneaster, hawthorn, linden, oak, rhododendron, and sycamore. Herbaceous plants susceptible to lace bugs include: aster, chrysanthemum, and scabiosa. The major plant-feeding lace bug species include Stephanitis spp., and Corythucha spp. Stephanitis spp. are primarily pests of broad-leaved evergreens, whereas Corythucha spp., including the sycamore lace bug (Corythucha ciliata) are pests of deciduous trees and shrubs.

LacebugDamagea

Fig 1:  Lace bug damage on azalea plant. Note the stippled and/or bleached appearance of the leaves.

 

Lace bugs feed primarily on leaf undersides; using their piercing-sucking mouthparts to withdraw plant sap from individual leaf cells. Their feeding cause’s leaves to appear stippled and/or bleached (Figure 1). Lace bugs feed similar to the twospotted spider mite, Tetranychus urticae, with both withdrawing chlorophyll (green pigment) from plant cells. The damage associated with lace bugs is similar to that caused by spider mites and leafhoppers; however, lace bugs leave black, tar-spot-like droplets of

LaceBugAdults2b

Fig 2: Black, tar-spot-like droplets of lace bug excrement.

excrement (“Lace Bug Poop”) on leaf undersides (Figure 2). The presence of black excrement distinguishes lace bugs from spider mites and/or leafhoppers. Excessive lace bug populations and extensive feeding may reduce plant vigor; however, any direct plant effects are dependent on plant age and size (especially young or newly-transplanted trees and shrubs).

Adult lace bugs are very distinguishable and quite attractive. The adults possess lacy, clear, shiny wings that are held flat over the body (Figure 3).

LB

Fig 3:  Close-up of lace bug adult.

 

They are 1/8 to 1/4 inch (3 to 8 mm) in length, and move sideways when disturbed. Female lace bugs lay between 20 to 50 eggs during their lifespan underneath leaves. The eggs are usually positioned alongside leaf veins and are black and shaped like a wine flask. Shiny, black nymphs with spines around the periphery of the body emerge from the eggs (Figure 4).

LaceBugImmatures

Fig 4: Lace bug nymphs on leaf underside.

Nymphs undergo five instar stages before reaching adulthood. Shed skins on leaf undersides are evidence of nymphs that have transformed into adults. The life cycle (egg to adult) generally takes about 30 days to complete. There may be up to three generations per year although development is contingent on temperature. Stephanitis spp. overwinters as eggs that are cemented onto leaves and Corythucha spp. overwinters as adults in bark crevices and branch crotches. Adult activity commences in the spring when leaves unfold.

Lace bugs are more abundant on plants such as rhododendron and azalea that are exposed to full sun rather than on plants in shady locations. The management of lace bugs is generally not warranted because lace bugs are susceptible to many natural enemies including predators; such as, green lacewings, plant bugs, assassin bugs, minute pirate bugs, and spiders. A forceful water spray may be effective in quickly dislodging lace bugs from plants. However, if necessary, a number of contact insecticides registered for use against lace bugs can be applied. Be sure to read the label to make sure lace bugs are listed. Be sure to thoroughly cover leaf undersides to maximize the effectiveness of spray applications because the leaf undersides are where all the life stages (eggs, nymphs, and adults) of lace bugs are located.

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

 

 

 

 

Euonymus Scale

–Dr. Raymond Cloyd

We are receiving inquiries regarding the presence of euonymus scale (Unaspis euonymi) crawlers on landscape plants such as 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 hatch over a two- to three-week period. The newly hatched crawlers, which may be noticeable migrating along the stem, start feeding near the base of host plants. Crawlers 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 later on in the season. Leaves eventually become spotted with yellow or white areas. Plants located near structures such as foundations, walls or in parking areas are more susceptible to euonymus scale than plants growing in open areas that receive sunlight and air movement. Furthermore, 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 (Figure 1), 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 (Figures 2 and 3). 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.

Figure1EuonymusScales

Figure 1 – Euonymus Scales

Figure2MaleandFemaleEuonymusScaleonLeaf

Figure 2 – Male and Female Euonymus Scale on Leaf

Figure3MaleandFemaleEuonymusScaleonLeaf

Figure 3 – Male and Female Euonymus Scale on Leaf

Cultural practices such as pruning out heavily infested branches—without ruining the aesthetic quality of the plant—is extremely effective in quickly reducing euonymus scale populations. 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. Applications of insecticides in May through June, when the crawlers are most active, will help to alleviate problems with euonymus scale later in the season. Insecticides recommended for suppression of euonymus scale populations that target the crawlers, 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. Check plants on a regular basis for the presence of crawlers, which will help time insecticide applications. In general, three to four applications performed at seven to 10-day intervals may be required although this depends 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), due to its high-water solubility (39,000 ppm), may provide suppression of euonymus scale populations when applied as a drench to the soil.

Euonymus scale is susceptible to a variety of natural enemies (e.g. parasitoids and predators). These include braconid and ichneumonid wasps, ladybird beetles, green lacewings, and minute pirate bugs. However, natural enemies may not provide enough mortality (‘killing power’) to significantly impact “high” 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 directly harmful to natural enemies, so applications of these materials may disrupt any natural regulation.

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