Farm Talk

Crops

October 15, 2013

K-State evaluates fall applications

Parsons, Kansas — Data from K-State research indicates November insecticide applications could reduce alfalfa weevil infestations the following spring.

The alfalfa weevil, one of the most well-known and devastating pests to agriculture, can cause serious defoliation in alfalfa during the spring, if not treated in a timely manner. Producers might have difficulty spraying insecticides timely in the spring, as spring alfalfa weevil activity can be intense for a period of three to six weeks, and spring weather is unpredictable.

Researchers at Kansas State University are evaluating an alternative treatment strategy that consists of spraying insecticides on alfalfa in the fall, followed by a spring application. Adult weevils become active in alfalfa fields in the fall where they feed, mate and start laying eggs in alfalfa stems, said Jeff Whitworth, K-State Research and Extension entomologist.

“We’re not trying to eliminate the weevils in the fall,” Whitworth said. “We’re just trying to reduce egg laying so that it will help out in the spring.”

In addition to Whitworth, the research team at K-State includes Alysha Soper, research assistant, and Holly Davis, insect diagnostician. The study began in the fall of 2012 to determine if a fall insecticide application significantly reduced spring infestations of the alfalfa weevil, and if so, what fall application timing would be most effective.

Understanding alfalfa weevil behavior is helpful in understanding the reasoning behind this study. The alfalfa weevil is a univoltine insect, Whitworth said, which means there is one generation produced each year. The weevils produced in the spring, from mid-March to mid-May, leave the alfalfa fields for the most part when temperatures get around 85 degrees Fahrenheit (85 F).

The alfalfa weevil can especially harm the first cutting, but the effects often transcend that first cutting to cause reduced quality and growth. Those weevils that aren’t destroyed in that first cutting will leave alfalfa fields and go to cooler and shadier places. A few stay in leaf litter in fields, Whitworth said, but most will come back in the fall to lay eggs around mid-October. The eggs, and some adult weevils, will over-winter inactively on the plant and in the leaf litter. Anytime the temperatures get above 48 F though, the weevils become active and continue laying eggs until temperatures cool again.

In the fall of 2011, Whitworth said chemical companies came up with registered insecticide fall application, which complied with the Kansas Department of Agriculture. It was too late in 2011 to test the fall application, so in 2012, the K-State research team put together a study to see if spraying adults in the fall would reduce spring infestation.

The researchers started the fall insecticide applications two weeks after detecting the first adult weevil. The first application last year was October 9, the second on October 23, the third on November 6 and the fourth on November 20. They evaluated alfalfa for weevils this spring on April 5 and April 12.

Results showed that the third application had less alfalfa weevils per stem compared to the other application dates.

“From a statistical standpoint, November 6 (insecticide application) showed significantly reduced infestation in the spring,” Whitworth said.

Although they were statistically reduced, Whitworth said from a practical standpoint they were not reduced enough to prevent significant damage if not treated in the spring. He said producers should keep in mind that most conventional synthetic-organic insecticides provide two to three weeks residual activity, and knowing this is helpful in determining the most effective application time to delay egg laying and eggs from hatching.

The findings are preliminary, based on one year of study, but the researchers studied large plots of alfalfa from six different fields. The researchers will continue studying this fall and evaluate again in the spring of 2014.

For more information about this research, see the publication online. £

1
Text Only
Crops
  • wheat_freeze_lodging.jpg Freeze could damage some Kan. wheat

    The hard freeze throughout Kansas in the early morning hours of April 15, could cause some damage to wheat, said Jim Shroyer, K-State Research and Extension crop production specialist. Wheat in the jointing stage is most at risk, he said.

    April 22, 2014 1 Photo

  • cornplantlatemay2.jpg WASDE report eases low crop price fears

    USDA’s April 9 World Agricultural Supply and Demand Estimates continued a series of recent reports that have offered corn and soybean producers a more optimistic grain-price outlook than what was expected for most of the winter, Purdue Extension agricultural economist Chris Hurt says.

    April 15, 2014 1 Photo

  • USDA: Corn acres expected to drop 4%

    The amount of American cropland devoted to corn is expected to shrink about 4 percent this year as farmers devote more acres to soybeans, the U.S. Department of Agriculture said last week.

    April 8, 2014

  • Bt-resistant rootworms ID’d in five states

    Researchers say bugs are developing resistance to the widely popular genetically engineered corn plants that make their own insecticide, so farmers may have to make changes.

    April 1, 2014

  • MU economist: Corn, bean price volatility next 5 years

    Expect volatility in the soybean and corn markets over the next five years, said Pat Westhoff, director of the University of Missouri Food and Agricultural Policy Research Institute (MU FAPRI).
    Look for corn prices to drop to $4 per bushel and soybean to $10 per bushel on average for the next five years, he said.

    March 25, 2014

  • marestail.jpg Plan now to control marestail in soybeans

    Controlling marestail in soybeans has been a big challenge for Kansas no-till producers in recent years.
    Because soybeans are generally planted later in the season, and marestail generally germinates in the fall or early spring, application timing and weed size are critical factors to successful control.

    March 18, 2014 1 Photo

  • Checking alfalfa for winter injury

    In the last couple of weeks, I’ve heard many concerns about alfalfa production for this spring.
    Cold temperatures and lack of snow cover are the two main issues producers are worried about for next season’s crop production, as certainly the alfalfa plant could die if exposed to extremely cold temperatures. In general, alfalfa plants can tolerate up to three weeks of winter injury before the plants are killed.

    March 11, 2014

  • soypods.jpg USDA reports on status of GE crops

    Genetically engineered (GE) varieties with pest management traits became commercially available for major crops in 1996.
    More than 15 years later, adoption of these varieties by U.S. farmers is widespread and U.S. consumers eat many products derived from GE crops — including corn-meal, oils, and sugars — largely unaware that these products were derived from GE crops.

    March 4, 2014 1 Photo

  • wheat-head.jpg Everest still leads Kan. wheat acres

    For the second year in a row, a variety of wheat developed by Kansas State University, is the leading variety in Kansas.

    February 25, 2014 1 Photo

  • RickReimer.jpg Innovation, exports fuel soybean demand

    Brent Hayek is revved up about potential new uses for soybeans, and he is piling up the miles to share his enthusiasm.

    February 18, 2014 2 Photos

Hyperlocal Search
Premier Guide
Find a business

Walking Fingers
Maps, Menus, Store hours, Coupons, and more...
Premier Guide
Seasonal Content