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ISSUE 1   May 10, 2007

UPDATES FOR THE 2007 NORTH DAKOTA FIELD CROPS INSECT MANAGEMENT GUIDE

There has been several additions to the 2007 North Dakota Field Crops Insect Management Guide that may be of interest to you. The web-version of the field guide has been revised.

http://www.ag.ndsu.edu/pubs/plantsci/pests/e1143w1.htm

Here’s a summary of the releases and new labels:

1) Latitiude (Gustafson LLC; active ingredients: 25% imidacloprid, 14% carboxin, 1% metalaxyl) for protection of seeds and seedlings of field corn, sweet corn, popcorn and sorghum against seed corn beetles, seed corn maggots, and wireworms as well as seedling diseases caused by Pythium and Phizoctonia. Apply as a seed treatment in the planter box prior to planting.

2) Mustang Max (FMC Corporation, active ingredient: zeta-cypermethrin) has a new label that includes sunflowers, canola, potatoes, alfalfa, and grass grown for seed, forage or hay. For sunflower, Mustang Max label includes seed weevils, sunflower beetles, stem weevil and other major sunflower insect pests. For canola, label includes flea beetles, grasshoppers, cutworms, and Lepidopterous insect pests. Major insect pests of potato that are on label are cutworms, leafhoppers, aphids, and Colorado potato beetle. Please see label for other crops.

3) Capture LFR (FMC Corporation; active ingredient: bifenthrin) ) has a new label that includes at-plant uses for dry beans and potatoes for control of grubs, seed corn maggots, and wireworms. This is good news because producers have been looking for an alternative to control wireworm in potatoes and dry beans. Capture LFR will directly mix into liquid fertilizer for controlling insects at-planting time. For grass, the label lists armyworms, grasshopper, plant bugs, aphids, potato leafhopper, cutworm, and more.

4) Preharvest Interval for Proaxis Reduced to 30 Days for Soybeans: Dow AgroSciences announces that the U.S. Environmental Protection Agency has accepted a label change regarding a reduced preharvest interval (PHI) for Proaxis insecticide (active ingredient: gamma cyhalothrin) in soybeans. Soybean growers can now apply Proaxis up to 30 days prior to harvest, compared with the previous label stating a 45-day interval. Proaxis is the latest-generation pyrethroid product for controlling a broad spectrum of pests that delivers quick knockdown.

5) Increased Rates for Fulfill in Potatoes: Syngenta Crop Protection announces that the U.S. Environmental Protection Agency has accepted a label change regarding an increased maximum application rate and the total amount applied per season for Fulfill insecticide (active ingredient: pymetrozine) in potatoes. The new maximum is 5.5 oz per acre per application and 11 oz per acre per season. Fulfill control is specific for aphid control.

6) Danitol (Valent USA Corporation; active ingredient fenpropathrin) did NOT received its approval from the U.S. Environmental Protection Agency for use in barley. Please cross it out from the "2007 North Dakota Field Crops Insect Management Guide" on page 23 under Aphids and 25 under Barley thrips and Cereal leaf beetle.

Remember, the label is the law. Always read and follow label directions.

 

TIME TO SCOUT FOR CUTWORMS IN ALL FIELD CROPS!

Early season cutworm activity has been reported in winter wheat in the southern tier and in canola in the north central regions of North Dakota. There are many different species of cutworms. When soil temperatures are above 40F, cutworms will become active. Cutworms damage plants by chewing and/or cutting the plant in the early stages of crop development. Generally, cutworms destroy more of the plant then they eat. Their numbers vary greatly from year to year and when numerous may destroy 50-75% of a crop! Cutworms feed at night and hide in soil during the day. Cutworm feeding activity usually extends from May through the end of June and young emerging plants are the most susceptible stage of crop development.

Cutworm photo
Cutworm (photo courtesy Clemson University -
USDA Cooperative Ext. Slide Series, www.forestryimages.org)

Scout fields once a week beginning with plant emergence. Once plants are larger, little additional injury will occur, for example, 6-leaf stage corn minimizes cutworm injury. Look for symptoms of leaf feeding (holes) and/or cut plants at several locations in each field. Pay special attention to poorly drained areas or places where weeds were present before planting. If cut plants are found, examine the soil around injured plants for cutworms.

Economic thresholds vary depending on the field crop:

  • Canola – 1 per square foot
  • Small grains – 4 to 5 cutworms per square foot
  • Corn – 3 to 6% of the plants cut and small larvae less than 1-inch present
  • Soybeans / Dry beans – 1 or more larvae per three feet of row or 20% of plants cut
  • Sunflower – 1 per square foot or 25-30% of plants cut
  • Alfalfa – 4 to 5 or more per square foot (new stands – only 2/sq ft)
  • Lentils – 2 to 3 cutworms per square meter (Canada)
  • Peas – 2 to 3 cutworms per square meter (Canada) Early detection is critical for effective control.
  • Cutworm control involves the use of postemergence foliar insecticides applied as a rescue treatments. Insecticide application is recommended in evening hours when cutworms are active. Treat if cutworms exceed the threshold and are 1-inch or less in length. Cutworms larger than 1-inch are mature and likely to pupate (cease feeding) before causing significant crop damage. Field crops with preventative treatments applied at or before planting (seed treatments) have given erratic control (only suppression), especially when cutworm numbers are high. Also, most fields do not have a cutworm problem every year so preventative treatments are unnecessary. Insecticides applied at planting time may be advisable if replanting is necessary due to cutworm problems and cutworms are 1-inch or less in length. Wet soil conditions will also improve insecticide efficacy, as cutworm fed near the soil surface in these conditions. Please see "2007 North Dakota Field Crop Insect Management Guide" for list of insecticides available on different field crops.

     

    2007 SECTION 18: TWO PESTICIDES ARE NOW AVAILABLE TO PROTECT THE STATE’S $23 MILLION HONEY CROP FROM VARROA MITES AND SMALL HIVE BEETLES

    The U.S. Environmental Protection Agency approved North Dakota’s request for Section 18 exemptions for Checkmite+ Bee Hive Pest Control Strips to control small hive beetles and Hivastan to manage varroa mites. Both small hive beetles and varroa mites can be devastating to beekeepers and can completely kill all bees in a hive if left uncontrolled. The exemption for Hivastan was needed because the resistance of varroa mites to many previously-effective insecticides is widespread. Both exemptions allow use of the products inside beehives. The use directions for both products prohibit use inside hives during honey flow. The exemptions expire Feb. 1, 2008. Hivastan is manufactured by Wellmark International; Check-Mite Strips are manufactured by Bayer HealthCare Animal Health Division. North Dakota is the nation’s leading honey-producing state. In 2006, the state produced 25.9 million pounds or 17 percent of the nation’s honey crop. For labels, see ND Department of Agriculture website below:

    http://agdepartment.com/Programs/Plant/Section18Exemptions.html

     

    GRASSHOPPERS ACTIVE IN PASTURES / RANGELANDS

    The recent rains have improved the forage situation in pastures and rangelands. High population of rangeland grasshoppers have been observed emerging in the North Central Region of North Dakota. Rangeland grasshopper species that are economically important in North Dakota include whitewhiskered, bigheaded (see photograph), migratory, Dawson’s, to name a few.

    Big-headed grasshopper
    Big-headed grasshopper (photo by G. Fauske, NDSU)

    See ND Grasshopper website.

    www.ndsu.nodak.edu/entomology/hopper/orthoptera_home.htm

    Grasshoppers cause defoliation by directly feeding on the leaf and stem tissues and cutting off leaves or stems. High populations of grasshoppers in pastures or rangeland can damage the plant crowns and grass plant may die under drought conditions. Rangeland grasshoppers rarely feed on field crops, except during years of very high populations, with the exception of migratory grasshoppers. Most of the rangeland grasshoppers overwinter as partial grown nymphs whereas most field crop grasshoppers overwinter as eggs. As a result, the rangeland species emerge earlier and as ‘large’ grasshopper nymphs, which usually become adults by the end of May or early June.

    Grasshoppers are cool-blooded and profoundly affected by temperature and relative humidity in their micro-environment. Warm temperatures can speed up grasshopper development where as cool temperatures retard all development. Increasing the time required for grasshoppers to mature generally increase juvenile mortality, which reduces defoliation and the number of eggs produced for next year’s grasshopper population. See Figure 1 for the effects of weather on grasshopper populations.

    Effects of weather on grasshopper populations
    Figure 1.  Effects of weather on grasshopper populations

    Grasshopper activity and feeding begins as temperatures in their micro-habitat rise above 65-70F. Cool-season grasses such as needlegrasses, wheatgrasses, and bluegrasses begin growth before most grasshoppers become active, and grow most rapidly when air temperatures are 65-75F. By the time infestation of grasshoppers begin to heavily defoliate plants, cool-season grasses have completed their growth and recharged energy reserves needed for spring growth next year. Warm-season grasses such as bluestems, grama grasses, and buffalograss do not begin growth until May-June and grow most rapidly when temperatures are 85-95F. Consequently, grasshoppers are most likely to damage warm-season grasses because they don't complete their growth until late summer.

    Economic thresholds for grasshopper densities in pasture or rangeland vary from eight to 40 grasshoppers per square yard. A program developed by USDA-APHIS called "Hopper" can be used to determine the threshold in individual situations depending on the cost of the insecticide, and projected forage yield and value. Please see website:

    http://www.sidney.ars.usda.gov/grasshopper/Support/index.htm

    For monitoring, one can count the number of grasshoppers hopping away from a visually delineated square yard or square foot areas as the scout slowly walks towards the marked area. However, the standard 15-inch sweep net is the most reliable and easiest method. Four 180-degree sweep equals a square yard and the number of grasshoppers can be counted.

    If grasshopper populations are above action thresholds, insecticides can be applied as a foliar spray or bait. An early application to grasshopper hatching areas is recommended to reduce high populations while grasshoppers are in early nymphal stages (young grasshopper nymphs are easier to control). Insecticides registered for use on pastures or rangeland for grazing or cut hay include: malathion, zeta-cypermethrin (Mustang Max), dimilin (insect growth regulator) and carbaryl (Sevin). See "2007 North Dakota Field Crop Insect Management Guide" or label for rates. Always read labels thoroughly before using any insecticide, and observe safety, pre-harvest intervals and grazing restrictions. Insecticide baits, once the most popular control method, have been replaced by foliar insecticide sprays. However, baits are still used occasionally in some circumstance on rangeland with short, dry vegetation. Carbaryl (Sevin) 5% bait is available. Some grasshopper species do not feed on baits so control may be limited. Attractiveness of bait affects efficacy and is reduced by rain and heavy dew.

    Research at the University of Wyoming has demonstrated the effectiveness of a new grasshopper control strategy in rangeland called RAATs (Reduced Agent/Area Treatment). The most effective insecticide used with this method is Sevin XLR (ultra low volume, aerial application) or dimilin. Sevin XLR is applied at half the recommended rate (8 fl oz per acre) instead of the full rate (16 fl oz per acre). In addition, only 50% of the area is treated leaving every other spray strip untreated. This methods cuts control costs and lowers the populations of grasshoppers in rangeland. Grasshopper control in the RAATs area lags behind control in full rate areas; however, in six days after treatment both treatments showed the same level of control. The reasons for this dramatic control are believed to be due to grasshopper movement into the treated strips while the insecticide is still effective, and to the preservation of natural enemies in the untreated strips.

    More information a grasshopper control on pasture or rangeland is available at the following website:

    http://www.sidney.ars.usda.gov/grasshopper/

     

    MANAGING SOYBEAN APHID SHORT COURSE VIDEOS AVAILABLE ONLINE

    If you missed the short course "Managing Soybean Aphids in 2007: How Will Biological Control Contribute?" that was held on March 6, 2007, videos (audio recordings synchronized with PowerPoint presentations) are now accessible from the North Central IPM Center Web site:

    http://www.ncipmc.org/teleconference/soybean2007/videos/

    The following topics were discussed during the short course and are available as separate video:

  • History and biology of the soybean aphid - David Voegtlin, Illinois Natural History Survey, Champaign, Illinois
  • Review of the situation with soybean aphids in the Midwest - David Ragsdale, University of Minnesota, St. Paul
  • Biological control of soybean aphids: What is it, and what do we have to work with in the Midwest - Bob O'Neil, Purdue University, West Lafayette, Indiana
  • The players: Predators, parasitoids, and pathogens--Dan Mahr, University of Wisconsin, Madison; Kelley Tilmon, South Dakota State University, Brookings
  • Practices to conserve and use natural enemies in soybean aphid IPM - Matt O'Neal, Iowa State University, Ames
  • Introducing new natural enemies into the U.S. - Bob O'Neil
  • Foreign exploration - Kim Hoelmer, USDA-ARS, Newark, Delaware
  • Host specificity testing - George Heimpel, University of Minnesota, St. Paul
  • Studies with non-target aphids - Cory Straub and Claudio Gratton, University of Wisconsin, Madison
  • Preparing for soybean aphids in 2007: Management guidelines, and the potential for biological control -
  • Chris DiFonzo, Michigan State University, East Lansing; Marlin Rice, Iowa State University, Ames
  • The short course was sponsored by the North Central Soybean Research Program.

    Janet Knodel
    Extension Entomologist
    Janet.Knodel@ndsu.edu


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