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Extension Entomology

Category: Field Crops

Field crop pest and beneficial organisms.

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.

 

 

Flower Wasps Getting Attention In Yards and Fields

Posted on by Sharon Schroll

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

 

A wasp commonly found during the summer in Kansas has recently caused concern among home owners and producers.  In one instance, several wasps were mistaken for wheat stem sawfly, a significant pest of wheat that has not yet established in Kansas.  Sometimes referred to as flower wasps, the Five-banded Tiphiid Wasp (Myzinum quinquecinctum), is a harmless solitary wasp found throughout most of the country. 

Male Flower Wasp

 

In Kansas, it is found statewide and is most common mid to late summer.  These ¾ to 1 inch long, narrow bodied wasps have dark bodies, long antennae and smoky wings.  Yellow markings are visible on their thorax and yellow bands are present on each abdominal segment.  Subtle differences set apart males and females.  Male wasps have yellow legs, while females have stockier orange-red legs and wider yellow bands on their abdominal segments.  Both male and females visit flowers to feed on nectar.  Females are parasitoids of various scarab beetle larvae, including common turfgrass pests such as white grubs, and have been promoted as biocontrol tools in farm and turf settings.  Female wasps seek out beetle larvae in the ground, digging for them with their stocky legs. She then deposits an egg on the body of the grub and injects a neurotoxin to paralyze it. As the wasp larva develops it will consume the beetle larva.  The wasp then overwinters as a pupa below the ground and emerges as an adult the following summer.  Since the populations of both the wasp and its host fluctuate yearly, the level of parasitism changes from season to season.  This results in some years where many wasps successfully overwinter and emerge in large numbers.

Male Wasps on Corn

The female wasps are not commonly encountered.  In fact, it is the male of this species that most often causes alarm.  This is due to the fact that the males tend to congregate together in large numbers on vegetation and occasionally even on home siding.  These groups are typically attracted to an area because there are nectar sources, shade or tall grass to shelter on over the evening.  When approached or disturbed, the group of male wasps take flight and fly circles around the location, giving the appearance of an angry swarm of wasps.  The males have no stinger and are harmless, however, the hooked appendage at the end of their abdomen is often mistaken for a stinger, adding to the alarm.  Despite their behavior and large numbers, these wasps are no threat to people, pets or landscaping. As summer progresses, these groups of male flower wasps will slowly die off and eventually disappear.

 

Soybean Pests

Posted on by Sharon Schroll

–by Jeff Whitworth, Field Crops — Entomologist

 

Soybeans finally seem to be starting to grow and develop a little since receiving some moisture and cooler weather. So, as the beans grow so do the soybean pests. Probably the number one pest all across the Midwest soybean growing regions is the bean leaf beetle (see fig 1). This time of year these beetles are feeding a little, which often causes the characteristic round and/or oblong holes in leaves (see fig 2), but also are actively depositing eggs in the soil around soybean stems. When this next generation of adults emerge then they will become active foliage feeders, and sometimes feed on succulent green pods-which may affect the bean inside the pod.

Figure 1: Bean leaf beetle

 

Figure 2: Leaf damage from bean leaf beetle

 

Green stinkbug adults (see fig 3) are also very active this time of year, much like adult bean leaf beetles, feeding a little but also depositing eggs. These eggs will be hatching over the next few weeks and the small stinkbug nymphs will also be very active sucking juice from host plants. Thus, as these soybeans grow and develop so will the pests. This indicates that monitoring should be initiated then in the next couple of weeks–or at least as the beans start into the reproductive phases, at which time they are at their most vulnerable to pest attack.

Figure 3: Adult green stink bug

(Photos by Cayden Wyckoff)

 

Grasshoppers

Posted on by Sharon Schroll

–by Jeff Whitworth — Field Crops, Entomology

Grasshopper eggs, deposited last fall, have been producing small nymphs for about the past 2 weeks. Thus, if field borders, weedy ditches, or any non-disturbed areas adjacent to crop fields are infested with these small nymphs- it is an ideal time to treat these areas to get good control (see fig 3).

Figure 3. Grasshopper nymphs

 

Potato Leafhoppers

Posted on by Sharon Schroll

–by Jeff Whitworth — Field Crops, Entomology

The 1st potato leafhoppers were detected in northcentral Kansas on 10 June, but probably started immigrating in a few days prior to that. They will continue this immigration for about another month. As of 14 June, however, only adults were active (see fig 1) but they are depositing eggs which hatch into very tiny nymphs in approximately 4-7 days. Much alfalfa, however, has just been swathed, or soon will be, and this will help mitigate potato leafhopper damage by removing eggs/nymphs before they cause any damage (see fig 2-often called “hopper burn”). However, adults will continue to migrate into these fields- so monitoring should continue as the new growth emerges.

Figure 1. Adult potato leafhoppers

 

Figure 2. Hopper burn

 

 

Army Cutworms (wheat, alfalfa)

Posted on by Sharon Schroll

–by Jeff Whitworth, Field Crops – Entomology

I have received a few calls within the last 10 days about “Miller moths” flying around lights at night and flying/running into the house when an outside door is opened the 1st thing in the morning. Those, at least from my experience and the specimens I have seen, are adult army cutworms (see pictures by Cayden Wyckoff). Like most adult cutworms, the army cutworm is a relatively thick bodied but otherwise nondescript moth. These moths are even more nondescript after losing wing scales while flying and/or hiding under objects during the day. They are a relatively agile, quick moving moth, and in Kansas always seem to be present just before and/or during Memorial weekend. As far as crops go, the army cutworm feeds on wheat or alfalfa since those were the crops growing last fall when the female moth was depositing eggs. Thus, since last fall the larvae have fed all winter and spring, pupated, emerged as adults, and are/or have headed for over- summering sites, usually somewhere in the Rocky Mountains. These same moths then, at least the ones that survive the summer, will be heading back this way in late summer or early fall and depositing eggs in wheat and alfalfa fields along the way. After depositing their eggs, these adult moths expire, but have started the next generation.

 

Adult army cutworm