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Extension Entomology

Fall Armyworms

Posted on by Sharon Schroll

–by Jeff Whitworth – Field Crop Entomologist

Adult fall armyworms are moths (fig. 1) and have been reported from southern Kansas for about the last 2 weeks and probably will be in the rest of the state soon-if not already. A quick refresher relative to this pest: they normally do not overwinter in Kansas, but in the lower portions of southern states, and down into Mexico and Central America. The moths usually arrive in Kansas anywhere from mid-June to mid-July as they fly/are blown here on southern winds. Fall armyworms have a wide host range but in Kansas are most often a cause for concern in corn and/or sorghum and later sometimes in wheat depending on planting date and weather. Also, in Kansas, especially the last 2 years, brome has been seriously defoliated (in combination with armyworms) in many areas around the state. Armyworm larvae may be part of the “ragworm” complex of larvae feeding in the whorl of corn and/or sorghum and then later the next generation become part of the complex of “headworms” or larvae feeding in the sorghum head directly on the developing grain. So the moths are here, ovipositing and thus the larvae are, or soon will, be feeding on whatever host the eggs were deposited on. Fall armyworms were quite common (in combination with other species) in 2020 and 2021 and thus monitoring should be initiated in any potentially susceptible crops. For management considerations please refer to the 2022 KSU Insect Management Guide for the crop of interest.

(Photo of fall armyworm moths taken of a Riker mount provided by revered KSU Extension entomologist, now retired, Dr. Bob Bauernfeind).

 

Figure 1: Fall armyworm moths

 

 

Scout for headworms in sorghum from flowering into milk stage

Posted on by Sharon Schroll

–by J.P. Michaud, Professor of Entomology, Agricultural Research Center, Hays, KS

Relatively new, cost effective, and environmentally friendly products are available for controlling headworms in sorghum. These are pest-specific viruses, formulated as biological pesticides that can be sprayed on the same as any foliar insecticide, or delivered via overhead irrigation sprinklers. But application must be made early in the infestation, while the majority of larvae are still small. These products should not be used as rescue treatments, but an early application will ensure infections propagate naturally throughout the field and that reapplication will not be required.  Sold under the brand names Heligen® (for corn earworm) or Fawligen® (for fall armyworm), these products are highly specific, killing only the target pest, sparing beneficial insects, and using other insects as vectors to create a local ‘epizootic’ of disease in the field. Thus, there is no environmental impact of treating below threshold (conventionally one or more worms per head), and it is valid to use these products as a relatively low-cost insurance policy, especially in a year when earlier sorghum to the south is already experiencing fall armyworm damage.

 

Farmers should be aware that many of the generic pesticides that might appear attractive on the basis of low cost are now much less effective against these pests, due to their repeated exposure to the same modes of action on many different crops over the years. In contrast, there are no known cases of pests evolving resistance to a virus, and unlike fungal pathogens, virus infections do not require humidity or leaf wetness. However, the product must be consumed by the pest, and larvae take up to a week to die, depending on temperature, but will stop feeding 48-72 hours post-injection. These virus formulations are also compatible with tank mixes of other materials, provided pH is held below 8.0, and combinations of both products are available if both species of headworms are present. More information is available from the supplier:

https://www.agbitech.us/

 

 

Green June Beetle Adult

Posted on by Sharon Schroll

–by Raymond Cloyd — Horticultural Entomologist

 

Green June beetle, Cotinis nitida, adults are flying around in massive numbers over both managed and unmanaged grassy areas. Green June beetle adults are erratic flyers and occasionally bump into people and objects. Adults are 3/4 to 1.0 inch long, velvety-green, with yellow-orange margins extend lengthwise on the front wings (Figure 1). The underside of the body is shiny and metallic green or gold. Adults fly around for several weeks from July through August. Green June beetle adults are sometimes mistaken for Japanese beetle, Popilla japonica, adults; however, they really do not look alike.

Figure 1. Green June Beetle Adult (Raymond Cloyd, KSU)

Green June beetle has a one-year life cycle, overwintering as a mature larva or grub in the soil. Adults typically emerge from late-June through early-July and are active during the day, resting at night on plants, in thatch, or in compost. Adults produce a sound when flying that is similar to bumble bees. Adults feed on ripening fruits and corn tassels, and may feed on the leaves of oak and maple trees. Male green June beetles swarm in the morning, flying to-and-fro just above managed and/or unmanaged grassy areas where females are located. The females emit an odor or pheromone that attracts the males. Clusters of beetles may be seen on the soil surface or in grassy areas with several males attempting to mate with a single female. After mating, females lay clusters of 10 to 30 eggs in moist soil with a high organic matter content. The larvae emerge (eclose) from eggs in approximately two weeks and feed near the soil surface. Larvae are 3/8 of an inch (early instars) to 1-1/2 (later instars) long and have the distinct characteristic of crawling on their back (Figure 2). Larvae primarily feed on organic matter in thatch or grass-clippings.

 

Figure 2. Green June Beetle Larva Crawling On Back (Raymond Cloyd, KSU)

 

For more information on how to manage green June beetle adults and larvae refer to the following extension publication:

 

Green June Beetle: Insect Pest of Turfgrass (MF3600 March 2022)

https://www.bookstore.ksre.ksu.edu/pubs/MF3600.pdf

Chinch Bugs

Posted on by Sharon Schroll

–by Jeff Whitworth — Field Crop Entomologist

 

Chinch bug populations seem to be increasing throughout south central and north central Kansas. Adults are currently very actively feeding, but more importantly, depositing eggs. This has been going on for the last couple of weeks in both corn and sorghum, which are still vulnerable to this chinch bug feeding, especially in later planted sorghum under hot dry conditions. Much sorghum is in the whorl stage or just starting to head out. Chinch bugs are usually difficult to control, but are especially difficult during these growth stages because, for the most part, the chinch bugs are feeding in and around the base of the plants and behind leaf sheaves. Either way they are relatively well protected from insecticides. The younger, tiny chinch bug nymphs are reddish with a white stripe while the older instar nymphs turn gray with a white stripe (see fig). For treatment recommendations please refer to the 2022 KSU Sorghum Insect Management Guide: https://www.bookstore.ksre.ksu.edu/pubs/MF742.pdf

 

The Soybean Gall Midge

Posted on by Sharon Schroll

— Anthony Zukoff — Southwest Research and Extension Center–Garden City, KS

 

The Soybean Gall Midge (Resseliella maxima) was first observed in Nebraska in 2011, but was not officially described as a new species until 2018 when this tiny fly established itself as an emerging pest of soybeans in South Dakota, Nebraska, Minnesota and Iowa.  New infestations have been documented every year since and its range has expanded into Missouri.  Soybean gall midge has been documented in Nebraska along the Kansas border as recently as 2021.  To date, soybean gall midge has not been documented in Kansas, however this pest should be actively scouted for during the growing season, especially in counties along the Nebraska border.  Losses from soybean gall midge infestation are due to plant death and lodging (Figure 1 Photo by Justin McMechan, UN-L).  Heavily infested fields have shown the potential for complete yield losses from the edge of the field up to 100 feet into the field and a 20% yield loss from 200 to 400 feet into the field.

Figure 1

Adults: tiny (2-3mm), delicate flies with an orange abdomen, slender bodies and mottled wings. Long legs are banded with alternating light and dark markings (Figure 2 Photo by Mitchell Helton, Iowa State University).

Figure 2

Larvae: small, legless, maggots that are clear to white-colored when young but turn bright orange when mature (Figure 3 Photo by Justin McMechan, UN-L).

 

Figure 3

Soybean gall midge overwinter as larvae in the first few inches of soil. After pupation in the early spring, adult midges emerge and lay their eggs on the lower portions of stems or at the base of soybean plants.  The eggs hatch and the larvae feed within the stems. Infestation does not occur until the V2 stage when natural fissures and cracks appear in stems allowing entry by larvae.  Infestation can continue into the reproductive growth stages. So far, there appears to be at least two generations per growing season.  The adult soybean gall midges do not feed on soybeans.

 

Scouting

Begin scouting soybean plants at the V2 growth stage.  Symptoms of infestation include:

  1. Wilting or dead soybeans along field edges with decreasing damage into the center of the field (Figure 4 Photo by Justin McMechan, UN-L)
  2. Darkening and swelling at the base of stems (Figure 5 Photo by Adam Varenhorst, SDSU)
  3. Brittle stems that break easily near their base
  4. Small orange larvae present in split open stems

Figure 4

Figure 5

Management

Being such a new pest, there are currently no published research-based management recommendations. On-farm studies in impacted states are examining the effects of cultural practices and insecticides on preventing losses.  Seed treatments have not shown to be effective.  Please report any occurrence of soybean gall midge to your local extension professional or contact the K-State Entomology Department.  The Soybean Gall Midge Alert Network (https://soybeangallmidge.org/) can be used to track developments regarding this new pest.

 

Control of Headworms in Kansas Sorghum –Research Spotlight

Posted on by Sharon Schroll

–by J.P. Michaud, Professor in Entomology–Agriculture Research Center, Hays, KS

Collaborative research in China was featured in this summer’s edition of American Entomologist, and is relevant to control of headworms in Kansas sorghum.

https://academic.oup.com/ae/article-abstract/68/2/4/6605209?redirectedFrom=fulltext

 

This work was done on ‘Old World bollworm’, H. armigera, but its biology is very similar to that of corn earworm, H. zea.

The mechanisms by which the virus manipulates host behavior described therein are likely the same as those used by the HzeNPV that is the organism in the Heligen product we are using to control corn earworm in sorghum.

Instead of trying to pupate in the soil, infected larvae climb to the tops of plants where they die, assisting in the dispersal of the virus.

Here is the full abstract:

 

Abstract

Baculoviruses can induce climbing behavior in their caterpillar hosts to ensure they die at elevated positions to enhance virus transmission, providing an excellent model to study parasitic manipulation of host behavior. Here, we demonstrate that climbing behavior occurs mostly during daylight hours, and that the height at death of Helicoverpa armigera single nucleopolyhedrovirus (HearNPV)-infected larvae increases with the height of the light source. Phototaxic and electroretinogram (ERG) responses were enhanced after HearNPV-infection in host larvae, and ablation of stemmata in infected larvae prevented both phototaxis and climbing behavior. Through transcriptome and quantitative PCR, we confirmed that two opsin genes (a blue light-sensitive gene, HaBL, and a long wave-sensitive gene, HaLW) as well as the TRPL (transient receptor potential-like channel protein) gene, all integral to the host’s visual perception pathway, were significantly up-regulated after HearNPV infection. Knockout of HaBL, HaLW, or TRPL genes using the CRISPR/Cas9 system resulted in significantly reduced ERG responses, phototaxis, and climbing behavior in HearNPV-infected larvae. These results reveal that HearNPV alters the expression of specific genes to hijack host visual perception at fundamental levels – photoreception and phototransduction – in order to induce climbing behavior in host larvae.

 

 

Grasshoppers

Posted on by Sharon Schroll

–by Jeff Whitworth — Field Crops Entomologist

Grasshoppers continue developing, mainly still in grassy/weedy areas, adjacent to crop fields.

These grasshoppers generally can fly for a short distance, but are not yet adults (see fig 3). As they continue feeding and developing however, and the hot/dry conditions continue, these grasshoppers will become adults, which means more mobile, and probably then fly to the more succulent crops nearby.

 

Figure 3: Grasshopper

 

Dectes Stem Borer

Posted on by Sharon Schroll

–by Jeff Whitworth — Field Crops Entomologist

 

 

Dectes stem borer adults have been active for about the past 3 weeks. Females have mated and started depositing eggs in stems for about the last 2 weeks. The small larvae are already causing an impact on young soybean plants (see fig2).

 

Figure 2: Soybean plant damaged by Dectes stem borer

Corn Earworms

Posted on by Sharon Schroll

–by Jeff Whitworth –Field Crops Entomologist

 

Most corn has recently tasseled, just is, or will be soon. 100% of all the ears we examined in the last 2 weeks, both sweet and field corn, were infested with at least one “earworm”. This is not unusual. All “earworms” were only one half to three fourths grown (see fig 1)

Figure 1: Corn ear worm

as of 18 July. Thus, these worms should cease feeding in the next 7-14 days, pupate in the soil for 4-7 days, and then emerge as adult moths. These moths will then mate and fly to a suitable host plant to start depositing eggs. Whether sorghum or soybeans depends upon the crop’s stage of growth when these moths are actively depositing eggs. Double cropped soybeans may be attractive to moths for another 1-3 months as the plants continue to set pods, and thus there could be another 1- 3 generations of larvae feeding on the bean within the pod. Sorghum, however, should only attract moths from flowering to soft dough–a much smaller oviposition window, but very critical because generally one larva causes 5% loss in grain.

 

 

Squash Bug

Posted on by Sharon Schroll

–by Raymond Cloyd – Horticultural Entomology

 

Squash bug, Anasa tristis, females have laid eggs and various stages of the nymphs are present feeding on squash and pumpkin leaves. Squash bug adults are flattened and 1/2 to 3/4 of an inch in length. Adults are dark-brown and have wings with brown-to-black and orange markings along the outer edge of the body (Figure 1). Females lay red-orange eggs on the leaf underside and top of leaves. Nymphs emerge (eclose) from the eggs in seven to 14 days and undergo five instars (stages between each molt) before maturing to adults. First instar nymphs that emerge from eggs have a red head and thorax (middle section) and pale-green abdomen (Figure 2). Second instar nymphs have a black head and thorax and a pale-green abdomen (Figure 3).

Figure 1. Squash bug adult (Raymond Cloyd, KSU)

Figure 2. Young squash bug nymphs (Raymond Cloyd, KSU)

Figure 3. Young squash bug nymphs (Raymond Cloyd, KSU)

Nymphs tend to gather near the eggs after emerging. Older nymphs (3rd to 5th instar) are gray (Figure 4) and tend to distribute themselves over the entire plant (Figure 5). Nymphs are 3/16 of an inch long and cannot fly because they do not have fully-developed wings.

Squash bug nymphs and adults use their piercing-sucking mouthparts to withdraw plant fluids from leaves, stems, vines, and fruits. Damage to leaves appears as small, yellow specks that eventually turn brown (Figure 6).

Figure 4. Older squash bug nymphs (Raymond Cloyd, KSU)

Figure 5. Older squash bug nymphs on the stem (Raymond Cloyd, KSU)

Figure 6. Feeding damage caused by squash bug (Raymond Cloyd, KSU)

Below are the plant protection strategies that you can implement to mitigate problems with squash bugs and prevent subsequent plant damage.

  1. Check plants for the presence of eggs, nymphs, and adults on leaf undersides at least once per week during the growing season.
  2. Destroy eggs, and remove (handpick) nymphs and adults, placing them into a container with soapy water to kill them. Handpick every three to four days.
  3. Place a floating row cover over plants to protect them from squash bug nymphs and adults.
  4. Position wooden boards throughout the garden, turning them over daily to collect squash bugs hiding underneath. You can kill the squash bugs by placing into a container of soapy water.
  5. Apply a contact insecticide when the nymphs are present. The smaller nymphs are easier to kill than the larger nymphs. Contact insecticides are less effective against adult squash bugs because adults have a thickened waxy cuticle (skin) that insecticides cannot adhere to and penetrate. Adults are also protected from insecticide sprays by the leafy plant canopy. Weekly applications of contact insecticides may be required to maintain populations below levels that will prevent plant damage. Thorough coverage of the leaf undersides is important to manage squash bug populations.

 

For more information on how to manage squash bug populations refer to the following extension publication:

 

Squash Bug (MF3308 July 2016)

https://www.bookstore.ksre.ksu.edu/pubs/MF3308.pdf