Crops

Brown wheat mites increasing in wheat fields

The brown wheat mites have been building up in the southwestern counties of Kansas the last couple of weeks. Controlling these mites is fairly simple, but the real question is whether to treat or not.

DNIM0023 Wheat CD 17Brown wheat mite damage can be quite severe when wheat is under drought stress. They can be especially prevalent in continuous wheat or where volunteer wheat was allowed to grow the previous season. They can be seen crawling around on leaves, on the soil surface and under debris/dirt clods during the day. These mites will easily drown if a driving rain of >0.3 inches occurs.  Also, irrigating infested wheat fields can quickly reduce populations.

Wheat CD 21The brown wheat mites look like pepper sprinkled on the leaves and will quickly drop off when disturbed. During windy days mites will not be as easy to spot as they will be around the plant base. No real threshold exists for the brown wheat mite, however it usually takes >200 mites per ft of row to justify chemical control in a unstressed crop. If young wheat looks fairly healthy and is not drought stressed, then the wheat will likely outgrow the mite damage. This may be slightly less if the young wheat is beginning to show signs of drought stress and mite numbers are building.  Heavy brown wheat mite feeding can cause the leaves to dry out and eventually die. Coupled with drought, severe infestations quickly kill young plants. The key is to 1) monitor fields for water stress and mite presence 2) determine if brown wheat mite infestations are large enough to warrant chemical treatment  3) decide if  the crop has the ability to bounce back if mite populations were lowered. If drought is taking a heavy toll on the crop then chemical control may not be economical. Keep in mind that some insecticides used for mite control can negatively affect beneficials and this can affect their ability to control later insect infestations in the wheat. It’s important to note that the presence of white eggs means the mites will soon disappear and control is probably not necessary. The presence of red eggs means more are soon to hatch.

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The winter grain mite (below) is another mite species that may be lurking in wheat fields this time of year. These mites can be confused with brown wheat mites, however their temperature preference, period of activity and color help to distinguish them. This mite prefers cool season grasses as well as winter wheat. They are far more picky about the weather, preferring cooler weather from just above freezing to 70F. The may be active during mild winters and can occasionally be found feeding under snow cover. Normal precipitation does not seem to thwart these mites, but heavy rains can reduce populations. They prefer to feed between dusk and dawn, but may also be active during a cloudy, cool day. During hot weather they may burrow down in the soil up to 4 inches. Their legs have a more pronounced orange-reddish color and they posses a dorsal anal pore. Their waste, in the form of a yellow liquid, can be seen exuding from the anal pore on top of their body in the picture below. The anal pore is located ventrally on the brown wheat mite. This can be seen with the help of a good hand lens.

For chemical control options, see here: http://www.ksre.ksu.edu/bookstore/pubs/mf745.pdf

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Photo from Oklahoma State University Small Grains Extension
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Why did the White-lined sphinx caterpillar cross the road?

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The last couple of weeks, these caterpillars have been seen roaming the streets in SW Kansas.

It’s hard to miss these finger-sized, brightly colored worms as they cross the road by the hundreds. So why are they crossing the road? To get to the other side where there is more food, of course! Many producers are spraying herbicide in and around fields in preparation for planting fall crops. The white-lined sphinx eats Kochia, pigweed and various other weed species which are common nuisance species in fields and pastures. Once the caterpillars’ food declines from the herbicide, the insects will migrate to the nearest green patch looking for food. Most of the time, these caterpillars will completely ignore crops and will concentrate on these weedy plant species. There are a few reports in the literature that recount brome grass as an occasional target of these caterpillars. Because of this, these caterpillars are generally regarded as beneficial!

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The white-lined sphinx caterpillars can have variable patterns and colors.

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The adults of the white-lined sphinx are very pretty moths that resemble hummingbirds. They can be spotted dashing about, stopping only for brief moments to nectar on flowers. These moths are common at dusk as well as during the day.


Update: Check for Southwestern Corn Borer

ImageSouthwestern corn borer larvae.

Southern counties across central and southwest Kansas are reporting high numbers of southwestern corn borer egg masses and are treating those fields now.

First-generation infestations begin in late June and consist of dark-spotted white worms that feed for five to 10 days on leaf tissue in the plant whorl, then move downward to begin tunneling within the stalk. The second (and most damaging) generation occurs in August. Adult moths begin emerging and laying eggs starting around July 15 to July 23, with egg-laying reaching a peak somewhere between Aug. 1 to Aug. 15. The exact time of the beginning and peak of egg-laying is influenced by weather and geographic location. Eggs are deposited on leaves primarily in the ear region. Newly hatched larvae begin feeding on leaves, but prefer to feed on ear shoots, husks, and silks. Within 10 to 12 days, this generation also begins tunneling within the stalk, generally below the ear zone.

     Insecticide applications should be considered on susceptible corn hybrids when 20 to 25 percent of the plants are infested with eggs or newly hatched larvae. Most corn was planted late in Kansas due to the late cold weather, so these fields could become heavily infested. Lodging, caused by girdling of stalk by the larvae, can be avoided if the corn is harvested before girdling begins. However in late planted fields, this is harder to achieve unless the corn is used for silage.

g07111art01SW Corn borer moth and larvae (Photo by Armon Keaster)

Eggs of the second generation are deposited at the ear zone or a node above or below the ear. A female moth is capable of laying 100 to 400 eggs in her short lifespan (approximately 5 days).

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Eggs are initially creamy white but develop three red transverse bars within 36 hours of being laid, and these bars remain until the larva’s emergence (approximately 5 days). (photos courtesy of Univ. of TN, Inst of Ag.)

NOTE: Corn hybrids containing European corn borer targeted Bt toxin should control both Southwestern and European corn borers, however, research suggests some Bt types are less effective for Southwestern corn borer control, therefore scouting fields that contain these Bt genes is important as well. K-state Efficacy trials in the past have shown that varieties in the Yieldgard family and Herculex family (see handy Bt table link below) work well for the second generation of SW corn borers, but may not provide 100% protection for the first generation. Since there are many new Bt products targeting moth larvae (Lepidopteran-above ground Bt) available today, K-State efficacy trials will begin in 2014 to evaluate the current hybrids.

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Check this Handy BT Table to see if your corn variety controls for corn borers.

http://labs.russell.wisc.edu/cullenlab/files/2013/05/Handy_Bt_Trait_Table.pdf

For addition information and control options for Kansas visit:

http://entomology.k-state.edu/extension/insect-information/crop-pests/corn/swcb.html


Check soybean fields for webworms

Webworms are being spotted in SW Kansas in double cropped and late planted soybeans. In Kansas, these moths can have multiple generations per year, with the bulk of the damage to soybeans occurring in July and August. Scout these soybeans fields often as these caterpillars can defoliate a young soybean crop in just a few days. There are two species, the garden webworm and the alfalfa webworm, that will attack soybeans.  Pigweeds are one of the preferred foods of the garden webworm. When these weeds are sprayed with herbicide, the larvae move in mass to their secondary host, soybeans. The alfalfa webworms will migrate from alfalfa after it has been harvested. High numbers of these moths have been seen flying in alfalfa fields recently, but harvesting the alfalfa will eliminate eggs the moths may have laid.
Image Garden webworm on pigweed.

ImageEarly instar webworm on soybean seedling.

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The garden webworm, Achyra rantalis. Webworms will line their feeding site with silk, often tying one or more leaves together.

ImageWebworm feeding damage in soybeans can be recognized by leaves having a window pane look with frass pellets mixed within the silk.

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ImageThe garden webworm can be easily distinguished from the green cloverworm by its appearance and damage.

The webworm has three spots in a triangle formation on each segment and 4 abdominal prolegs, while the green cloverworm has no spots and has three abdominal prolegs. The green cloverworm chews irregular holes in the leaves and will not clump leaves together with silk. Both of these larvae can act erratically when disturbed.

For control options in soybeans :

http://entomology.k-state.edu/extension/insect-information/crop-pests/soybeans/webworms.html

Green cloverworm:

http://entomology.k-state.edu/extension/insect-information/crop-pests/soybeans/gcw.html 


Too hot for the grasshoppers!

 Thousands of grasshoppers try to escape the 108+ degrees that we had last week by climbing anything in sight! These photos were taken in Holcomb, KS (Finney Co.) by Ken Robinson.

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SPREAD THE WORD…Save OUR beneficials and pollinators

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HELP SPREAD THE WORD

The large bumblebee kill event that recently occurred in Oregon indicates a need to remind users of pesticides about the absolute importance of reading and following the label – and to pay particular attention to WARNINGS.

With agricultural production in full swing all across the country, USDA requests your assistance through outreach and education to remind all users of pesticides of the importance of following the label. This helps to ensure good pest management while protecting wildlife, their habitat, and the environment. It is especially important that urban gardeners and homeowners, who may not be as familiar with the content of the label, have access to this important information.

Use of any pesticide in any way that is not consistent with label directions and precautions is illegal. It may also be ineffective and dangerous.

What to communicate to your community:

  • Choose the form of pesticide best suited to your target site and the pest you want to control:First, identify the problem correctly and then, choose the least-toxic pesticide that will achieve the results you want and be the least toxic to you and the environment.
  • When the words “broad-spectrum” appear on the label, this means the product is effective against a broad range of pests. If the label says “selective,” the product is effective against one or a few pests.
  • Read the label before buying the pesticide, read the label before mixing or using the pesticide each time, and read the label before storing or disposing of the pesticide.
  • Determining the right amount to purchase and use: do not assume that using more pesticide than the label recommends will do a better job . It won’t.
  • Find the signal word—either Danger, Warning, or Caution on the pesticide label. The signal word tells you how poisonous the product is to humans.
  • Choose the form of pesticide (aerosol, dust, bait, or other) best suited to your target site and the pest you want to control. Certain formulations work better for some pests and/or some target areas than others
  • Using the product safely and correctly
  • Never apply pesticides outdoors on a windy day (winds higher than 10 mph)
  • Wear protective clothing, don’t smoke or eat
  • Mix and apply only the amount you need
  • Watch for negative effects on wildlife (birds, butterflies, and bees) in and near treated areas. If you see any unusual behavior, stop using that pesticide, and contact EPA’s Pesticide Incident Response Officer
  • Store and dispose of pesticides properly.
  • Follow all storage instructions on the pesticide label.
  • Always store pesticides in their original containers, complete with labels that list ingredients, directions for use, and first aid steps in case of accidental poisoning.

**State and local laws regarding pesticide disposal may be stricter than the federal requirements on the label. Be sure to check with your state or local solid waste agency before disposing of your pesticide containers.

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Breaking news: 50,000 Bumblebees DEAD

Image“largest documented die-off of bumblebees”

As the estimate of dead bees rose to 50,000, the Oregon Department of Agriculture confirmed the insecticide Safari caused the deaths in a Wilsonville earlier this week. A landscaping company sprayed 55 linden trees in a Target parking lot to control for aphids.

Safari’s main ingredient is dinotefuran, a neonicotinoid.

News Story here:

http://www.oregonlive.com/environment/index.ssf/2013/06/pesticide_confirmed_in_bee_dea.html#/0

http://www.oregonlive.com/environment/index.ssf/2013/06/state_agency_temporarily_bans.html

Photo essay here:

http://photos.oregonlive.com/photo-essay/2013/06/dead_bumble_bees_prompt_invest.html

“Because neonicotinoids are long-lasting in plant tissues and can be found in flower nectar and pollen, and because they have been implicated in the global decline of honey bees, there have been growing concerns about their safety for pollinators.”

more here: http://www.xerces.org/2013/06/27/scientists-call-for-an-end-to-cosmetic-insecticide-use-after-the-largest-bumble-bee-poisoning-on-record/