Kansas State University

search

Extension Entomology

Month: July 2019

Soybean Pest Update

–by Dr. Jeff Whitworth and Dr. Holly Davis

Soybeans appear to be relatively pest free at the present time – but looks can be deceiving.  There are a few small green cloverworms, thistle caterpillars, soybean podworms (corn earworms) and webworms, along with stink bugs and spider mites.

These pests are probably only going to increase in the next few weeks.  Bean leaf beetle adults will also likely be emerging and showing up in fields soon.  As the beans continue to develop so will the pests, thus monitoring should continue until beans senesce.

 

Sorghum “Ragworms”

–by Dr. Jeff Whitworth and Dr. Holly Davis

Much of the sorghum around north central Kansas is at, or just coming into, the whorl stage.  As the leaves unfurl and grow out of the whorls, a pretty high number of plants are showing large holes that have been chewed in leaves.  These holes are from smaller larvae (most that we have sampled are corn earworms) that feed on the leaves while they are still furled. When leaves grow out of the whorl they have showy, ragged looking feeding that may cause concern.

Larvae sampled this week still have about one additional week of feeding within these whorls, then they will exit and crawl down the plant to pupate in the soil.  Larvae in the whorl are rarely worth spraying for four reasons: 1) by the time the leaves unfurl making feeding damage visible, most larvae have already accomplished most of their development and thus feeding, 2) insecticides usually can’t penetrate far enough down into the whorl to actually impact the larvae, 3) a general insecticide will kill most beneficial insects, and 4) ragged looking leaves during this stage have little to no effect on yield, and no, you cannot eliminate the next generation by spraying this generation.

 

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.

 

 

New Extension Publication

–by Dr. Raymond Cloyd

We have a new extension publication available entitled, Scale Insect Pests

 

This new extension publication provides information on the biology, scale types, plant damage, and offers strategies for managing specific types of scales. There are color images of the scale insect pests found in Kansas and surrounding states. The extension publication is available from the following website:

https://www.bookstore.ksre.ksu.edu/pubs/MF3457.pdf

 

MORE – Japanese Beetles

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Japanese beetle adults have also been emerging over the past week or two.  These adults will feed on just about any pollen, nectar, or succulent plant source for a few days then disperse to begin ovipositing into the soil.  The adults may attack emerging silks in corn or new succulent leaves in soybeans, but typically only around the edges of fields.

Dectes Stem Borers

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Dectes stem borer adults continue to emerge throughout north central Kansas.  These adults are currently aggregating mainly around field borders and most commonly on ragweed.  They will start dispersing into soybean fields within the next week to 10 days, as they do every year, to begin oviposition.  The adult females are relatively mobile and move from plant to plant inserting eggs into, or just below, the petioles of many plants.  This oviposition period may last for four weeks or more and may be spread throughout the field! This is one reason why controlling dectes stem borers with an insecticide is so difficult – timing of application.

Eggs hatch in the stem and the small larvae start feeding/boring their way to the main stem and then down this stem to the soil surface.  They usually reach the soil line in late August and larvae girdle their way around the inside of the stem, weakening the stem and often leading to lodging, especially if there are strong winds.  This lodging is responsible for most yield loss.  For more information regarding dectes stem borers, please see Dectes Stem Borer, MF2581: https://www.bookstore.ksre.ksu.edu/pubs/MF2581.pdf

For more information on soybean pest management, please refer to the KSU Soybean Insect Management Guide: https://www.bookstore.ksre.ksu.edu/pubs/MF743.pdf

Japanese Beetles

— by Dr. Raymond Cloyd

Japanese beetle, Popilla japonica, adults are present in most regions of Kansas feeding on different plant species, including: roses, Rosa spp.; littleleaf linden, Tilia cordata; and Virginia creeper, Parthenocissus quinquefolia, among many other plant species. The ways to manage populations of the adult stage of Japanese beetle are limited, and have been for many years, with the use of insecticides still being the primary strategy. Japanese beetle adults are one of the most destructive insect pests of horticultural plants in landscapes and gardens. Furthermore, the larva or grub is a turfgrass insect pest in home lawns, commercial settings, and golf courses.

 

Japanese beetle adults are 9/16 of an inch long, metallic green with coppery-brown wing covers, and about 14 tufts of white hair are present along the edge of the abdomen (Figure 1).

Fig 1. Japanese Beetle Adults Feeding On Leaf (Auth–Raymond Cloyd, KSU)

Adult Japanese beetles emerge from the soil and live up to 45 days feeding on plants over a four-to-six-week period. Adults feed on many horticultural plants including: trees, shrubs, vines, herbaceous annual and perennials, vegetables, fruits, and of course—roses. Plant placement in the landscape and the volatiles emitted by plants are factors that affect adult acceptance. In addition, Japanese beetle adults produce aggregation pheromones that attract males and females to the same feeding location. Adults can fly up to five miles to locate a host plant; however, they tend to only fly short distances to feed and for females to lay eggs.

Japanese beetle adults feed through the upper leaf surface (epidermis) and leaf center (mesophyll), leaving the lower epidermis intact. Adults avoid feeding on tissue between leaf veins, resulting in leaves appearing lace-like or skeletonized (Figure 2).

Fig 2 Japanese Beetle Adult Feeding Damage On Leaf (Auth–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 to flower. Japanese beetle adults start feeding at the top of plants, migrating downward after depleting food sources. Japanese beetle adults will also feed on flowers (Figure 3),

Fig 3. Japanese Beetle Adults Feeding On Rose Flower (Auth–Raymond Cloyd, KSU)

chewing holes in flower buds, which prevents flowers from opening or causes petals to fall prematurely.

Managing Japanese beetle adult populations involves implementing a variety of plant protection strategies, including: cultural, physical, and applying insecticides. Cultural control is affiliated with maintaining healthy plants through proper irrigation, fertility, mulching, and pruning, which are important in minimizing ‘stress’, and may possibly decrease susceptibility. Moreover, removing weeds that are attractive to Japanese beetle adults such as smartweed (Polygonum spp.) may help to reduce infestations. Physical control involves hand-picking or collecting Japanese beetle adults from plants 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, for at least three weeks, particularly after adults emerge, may substantially reduce plant damage. A study reported that collecting Japanese beetle adults daily at 7:00 pm had the greatest impact on populations and reduced subsequent damage.

 

In general, the use of Japanese beetle traps (Figure 4) in a landscape or garden is not recommended since the floral lure and synthetically-derived sex pheromone may attract more adults into an area than would ‘normally’ occur. Japanese beetle adults may also feed on plants before reaching the traps, which increases potential damage.

 

Spray applications of contact insecticides will kill Japanese beetle adults. However, repeat applications are required; especially when populations are excessive. Several pyrethroid-based insecticides; such as those containing permethrin (Sevin®), bifenthrin or cyfluthrin as the active ingredient, will suppress Japanese beetle adult populations. However, most of these insecticides will also directly harm many natural enemies (parasitoids and predators) and continual use will result in secondary pest outbreaks of other pests including the twospotted spider mite, Tetranychus urticae. In addition, 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 against Japanese beetle adults because they have to feed on leaves and consume lethal concentrations of the active ingredient. If extensive populations are present, plant damage can still occur.

 

PHOTO NOT AVAILABLE

The battle against Japanese beetle adults requires diligence, patience, and persistence, to prevent adults from causing substantial damage to plants in landscapes and gardens.

 

 

Subscribe By Email

Get every new post delivered right to your inbox.

This form is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.