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Extension Entomology

Month: August 2018

Volunteer Wheat

–By Dr. Jeff Whitworth and Dr. Holly Schwarting

Again, please remember every moisture event prompts the growth of volunteer wheat.  This volunteer wheat needs to be controlled at least 2 weeks prior to planting to help mitigate all wheat pests;  pathogens, mites, and insects.

 

Sorghum Update – ‘Headworms’, Beneficials, and Aphids

–By Dr. Jeff Whitworth and Dr. Holly Schwarting

Sorghum continues to get the attention of many pests and beneficials.  Chinch bug populations are not diminishing even though they are not as noticeable because most are feeding around the base of the plants and behind leaf sheaths on the stalks.  Much late planted, or at least slower developing, sorghum is still vulnerable to these chinch bugs.  Bugs may also move up to the heads as they emerge from the whorl to feed on the forming kernels that provide a succulent source of nutrients.

‘Sorghum headworms’, mostly corn earworms but also a few fall armyworms, are infesting all sorghum fields (not yet in the soft dough stage) that we monitored throughout north central Kansas.  Most fields have close to, or are exceeding, 100% infestation levels (1 or more larvae/head).  These larvae are present in all different sizes, or developmental stages, from 1st to 4th instars.  Thus, they will be feeding on these kernels for at least another 7 – 10 days.

Remember, between flowering and soft dough, these larvae will cause 5% yield loss/ worm/ head.  Very few beneficials are available to help control headworm populations.  However, there are huge populations of beneficials currently present to help control any aphid pests that are, or might be present in the near future.

 

 

Corn leaf aphid populations were common on earlier planted sorghum, and still are on later planted sorghum that is just reaching the whorl stage.  These corn leaf aphids have really helped fuel the beneficial populations.  Fields that have headed out are swarming with lady beetle adults and larvae, syrphid or hover flies, green lacewings, and parasitic wasps.

 

 

 

Sugarcane aphid (SCA) populations are becoming scattered around north central KS, slowly so far, and are really attracting the attention of all these beneficials, which will hopefully help control colony growth.

For management considerations and recommendations for these, and other sorghum pests, please refer to the 2018 Sorghum Insect Management Guide:   https://www.bookstore.ksre.ksu.edu/pubs/mf742.pdf

 

 

New Extension Publications – Pesticides and Bees; Squash Bug and Squash Vine Borer

–by Dr. Raymond Cloyd

Pesticides and Bees

This extension publication is intended to increase awareness of the impact of pesticides on bees and offer suggestions on how to protect bees from pesticide exposure. It describes how bee behavior influences pesticide exposure and toxicity, and why laboratory studies reach different conclusions than what researchers have observed in the field. Benefits and risks associated with specific types of pesticides and application methods are discussed, as well as, complex pesticide interactions, which increase risks to bees but are not well understood. Below is the link to retrieve a PDF file of the extension publication:

 

https://www.bookstore.ksre.ksu.edu/pubs/MF3428.pdf

 

 

Squash Bugs and Squash Vine Borer

Both squash bug and squash vine borer are still creating havoc in vegetable gardens throughout Kansas. What can you do to alleviate the damage caused by these insect pests? Well, there are extension publications on both insect pests that were up-dated in 2016 by Drs. Raymond Cloyd and James Nechols. Below is the link to these extension publications:

 

  1. Squash Bug

 

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

 

 

  1. Squash Vine Borer

 

https://www.bookstore.ksre.ksu.edu/pubs/MF3309.pdf

 

Soybean Update – Defoliators and Podworms

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Soybeans seem to be attracting the attention of many different types of pests, including many defoliators.  Currently, they are mainly green cloverworms, yellowstriped armyworms, and thistle caterpillars.  Fortunately, populations of these species, or any others for that matter, have not reached densities that have warranted insecticide applications, for the most part.

Unfortunately, soybean podworm (a.k.a. corn earworm/sorghum headworm/cotton bollworm) populations are on the increase in south central and north central Kansas.  These worms eat right through the pod to get at, and consume, the seeds within.  So, as the seeds are filling, they are susceptible to being fed upon by these podworm larvae.  They will feed on smaller, more succulent beans for 10-14 days, then cease feeding to pupate.  Since they are feeding directly on the marketable product, it doesn’t take much of this feeding to reduce yield.

 

 

One important point to remember relative to treating for soybean podworms: these are contact insecticides and thus they must physically contact the targeted pest.  Therefore, you need to utilize enough carrier (water) to penetrate throughout the soybean canopy to get to where these larvae are feeding.  But, you need to do this while the larvae are still small and before they have negatively impacted the yield.  There will probably be at least one more generation this year, so monitoring needs to continue as long as plants are adding pods and there is succulent green reproductive tissue to feed on.  For treatment thresholds and insecticide information, please refer to the 2018 Soybean Insect Management Guide available at: https://www.bookstore.ksre.ksu.edu/pubs/mf743.pdf

 

Sugarcane aphid expanding to new counties in Kansas

New detections of sugarcane aphid (click here for identification and management information) have been reported this week for Kansas counties: Kearney, Pawnee, Scott, Finney, Comanche, Reno, Barton and Saline.

Several fields in Finney, Ford, Meade, and Pratt have reached threshold levels and have been treated. However populations reported from the other counties remain low and were found on only a few hot spots within a field. Remember that hot weather can increase SCA numbers rapidly! See current map here.

Note that the economic threshold is 20% of pre-boot plants infested with established colonies (>100 aphids), or 30% of plants infested post-boot.

Treatment options are either Transform (1 oz per acre) or Sivanto (4 oz per acre). For earlier stage plants, Sivanto will provide a longer period of protection, but is about 40% more expensive. For plants that have headed out, Transform will be a more economic option, as a long period of residual activity will be less important, and it is also safer for the beneficial species. For a list of products and labels, visit the myFiels.info Insecticide Selector.

DO NOT mix these products with any organophosphates or pyrethroids or any combinations thereof – it will actually reduce their efficacy.

If there is a need to control headworms, these products can be mixed with either Prevathon or Blackhawk, but nothing else.

For help with scouting and identification, click here to see instructions and pictures.

To see local management information, click here.

For more help, contact your local Extension office. Find yours by clicking here.

 

Volunteer Wheat

–by Dr. Jeff Whitworth and Dr. Holly Davis

 

It is once again time to control volunteer wheat!  This needs to be done at least 2 weeks prior to wheat planting and will help mitigate problems with Hessian flies, wheat curl mites, wheat aphids (Russian, bird cherry-oat, greenbug, etc.) and diseases.

Sorghum Update – ‘Ragworms’, ‘Headworms’, and Aphids

–by Dr. Jeff Whitworth and Dr. Holly Davis

Late planted sorghum is still causing considerable concern throughout north central Kansas as the leaves grow out of the whorl and are significantly ‘chewed up’ looking.  These ‘ragworms’, primarily corn earworms and fall armyworms but also a few cattail caterpillars, are still active in younger plants.

 

As these plants reach reproductive stages, i.e. flowering, there will be a high probability of having ‘headworms’ (corn earworms and fall armyworms) infesting the kernels.  Sorghum heads are the most vulnerable between flowering and soft dough.  There are currently significant infestations of these headworms throughout north central Kansas with worms in various stages of development.  Headworms cause approximately 5% loss per worm, per head.

 

There are large numbers of corn leaf aphids, greenbugs, and even a few yellow sugarcane aphids around north central Kansas.  The first report of a sugarcane aphid colony from Saline Co. was made on 16 August. These aphids are attracting, and providing food for, large numbers of beneficials which seem to be keeping aphids relatively well controlled.  Insecticide applications have not been needed for aphids. More information on sugarcane aphids in Kansas can be found at My Fields: https://www.myfields.info/pests/sugarcane-aphid

 

For more information regarding sorghum insect pest management please refer to the KSU 2018 Sorghum Insect Management Guide: https://www.bookstore.ksre.ksu.edu/pubs/mf742.pdf

Red-Shouldered Bug

–by Dr. Raymond Cloyd

Red-shouldered bug, Jadera haematoloma, nymph and adult populations can be found gathering on the south and west sides of golden-rain trees, homes, and buildings; sometimes in extensive numbers. These insects are similar in appearance to the boxelder bug, Leptocoris trivitatus (Figure 1);

Fig 1. Adult boxelder bug (Author–Raymond Cloyd, KSU)

however, adults lack the central red stripe on the pronotum of the thorax, and red markings on the wings. Instead, red-shouldered bugs have a distinctive red line on both sides of the thorax or ‘shoulder.’ Red-shouldered bugs are somewhat flattened and 3/8 to 5/8 inches long (Figure 2).

Fig 2. Adult red-shouldered bug (Author–Raymond Cloyd, KSU)

 

Nymphs resemble the adults in appearance but are more oval-shaped and have wing pads—but not wings. Adults overwinter in a protected location including homes. They will also overwinter in the soil or leaf litter near building foundations. Red-shouldered bugs feed primarily on the seeds of the golden-rain tree, Koelreuteria paniculata. Both nymphs and adults can be found aggregating on the trunk of trees (Figure 3).

Fig 3. Red-shouldered bugs aggregating on the bark of golden-rain tree (–Raymond Cloyd, KSU)

Red-shouldered bugs can become a nuisance later in the season when they enter homes and buildings to overwinter. They do not transmit any diseases that we are aware of. The red-shouldered bug is native to the United States.

The main way to manage red-shouldered bugs from entering homes and buildings is by sealing or caulking cracks and crevices. Applying an insecticide to the outside of a home or building such as carbaryl (Sevin) or one of the pyrethroid-based insecticides (e.g. bifenthrin, cyfluthrin, or permethrin) may reduce the number of adults that enter homes or buildings. Once red-shouldered bugs enter homes or buildings, however, there are few effective management options other than vacuuming them up, and disposing of them from the bags outdoors. If you have any questions regarding red-shouldered bugs contact your local extension office or a university-based extension entomologist.

 

Sorghum Update – Chinch bugs, Headworms, and Corn Leaf Aphids

–by Dr. Jeff Whitworth and Dr. Holly Davis

 

Chinch bug populations continue to increase dramatically throughout north central Kansas.  Adults are still active, mating and ovipositing in both the developing heads and around the base of plants.  There are also large numbers of nymphs, mainly feeding in and around the base of plants, but some are on the developing kernels.  The significant populations of chinch bugs, along with continued hot and dry conditions, are causing some plants to lodge as the stalks dry down prematurely.

 

‘Headworms’, both fall armyworms and corn earworms, are also very common in all the fields we sampled that were in the flowering stages.  On 6 August, there were all different sizes of larvae detected in heads.  Many fields throughout north central Kansas are just starting to reach the reproductive stages, so these ‘headworms’ will continue to be problematic in any field that is in the flowering to soft dough stage.  Past research has indicted that ‘headworms’ may cause approximately 5% loss/worm/head.  It is important to sample in a timely manner to detect these pests while they are still small, before most of the feeding damage has been done.

 

Corn leaf aphids (CLA) continue to cause considerable concern throughout north central Kansas as these populations are still very widespread and become more apparent as the heads start to extend out of the whorl.  However, there are many beneficials present as well.  CLA should have little to no negative impact on plant development or yield other than potentially a few individual plants.

 

For more information relative to sorghum insect management, please see the 2018 Sorghum Insect Management Guide: https://www.bookstore.ksre.ksu.edu/pubs/mf742.pdf

 

 

 

 

Soybean – Bean Leaf Beetles and Defoliators

–by Dr. Jeff Whitworth and Dr. Holly Davis

Soybean fields around north central Kansas still seem to be relatively unbothered by defoliators.  Bean leaf beetle adults are increasing in numbers and may begin feeding on the succulent pods as they form.

The next generation of corn earworms (coming from sorghum fields) may start feeding on the beans within the pods, although we did not find any pod feeding yet.  The only defoliators sampled this past week were a few green cloverworms, thistle caterpillars, and yellowstriped armyworms.  None were in sufficient numbers to cause concern, individually or collectively.

For more information relative to soybean insect management, please see the 2018 Soybean Insect Management Guide: https://www.bookstore.ksre.ksu.edu/pubs/mf743.pdf

 

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