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ISSUE 12  July 20, 2000



    The armyworm treatment decisions are getting tougher. As we approach harvesting, armyworms still pose a threat to small grains through head clipping. The treatment threshold recommended when head clipping occurs is 2 armyworm per square foot. There have been reports of populations as high as 10 to 14 per square foot in northwest Minnesota. So far, North Dakota has not had the high populations found just to the east. Armyworm populations in the Red River Valley have been in
the 1 to 4 per square foot range, when detected. These are still potentially troublesome numbers and scouting to determine infestations and damage are warranted.

    Crops adjacent to small grains or grassy areas where armyworms are present should be scouted for migrating worms. As food is depleted or declines in quality, armyworms will move in search of more to eat. Treating field margins ahead of the migrating larvae will halt their progress.



    The only reports of major activity continue to come from northwest North Dakota. Divide County has had populations large enough to justify treating. Areas south and east, towards Minot, have also had isolated fields with treatable levels. Several reports of threshold levels were from fields that were wheat on wheat.

    Continue to watch fields that are heading to early flowering in all northern ND counties. We are past peak emergence but significant adult activity can continue for the next 5 to 7 days. As expected, populations were down through most of the areas where midge have posed a problem. Finding the few fields with significant activity has been a challenge.



    Sanitation is an important program for preventing insect infestations. It is also critical to be thinking about storage of grain and things necessary to keep insects and other storage problems to a minimum. Last year, there were many problems associated with insects in stored grain that can be avoided with proper planning and handling.

    1. Clean outside around the bin, beneath perforated floors and inside ducts in addition to cleaning the bin. Sweep or vacuum grain dust and old grain from floors, walls and ceilings where hiding places exist for stored grain insects. If you can tell what has previously been in the bin, it is not clean. In bins where the perforated floor cannot be easily removed, chloropicrin grain fumigant can be applied to control insects in the sub-floor area. Chloropicrin is a highly toxic chemical and as such, all label
instructions and safety measures must be carefully adhered to. Debris and grain spills outside the bin also encourage rodents and insects which can then move in through openings.

    2. When possible, avoid filling bins with new grain where some old grain is already present. This creates an ideal situation for insects in the bran bug group (sawtoothed grain beetles, flour beetles and the like).

    3. Roof leaks commonly lead to columns of spoiled grain. Check for these leaks by looking for light coming into the bin. Moisture coming into the bin through the seal between the bin and concrete will cause spoilage around the perimeter of the bin at the base. Check the seal since sealants do deteriorate. Water will run away from the seal at the base of the bin wall if the concrete is sloped away from the bin. Also check the seals around the doors and hatches.

    4. After cleaning and repairing, use a residual bin spray to treat the insect surfaces of the bins at least two weeks prior to filling. Recommended bin sprays are methoxychlor 2 lb EC, Reldan 4 lb EC or Tempo, applied according to label directions.

    5. If grain is to be held in storage for a year or more, it should be treated with a grain protectant such as malathion or Reldan. Be aware, however, that malathion will not control Indian meal moths, which commonly infest stored commodities in the state, and neither Reldan nor malathion will control lesser grain borers. Bacillus thuringiensis (Bt) sold as Dipel can be used as a surface treatment to control Indian meal moth, but it will not have any affect on beetle infestations (e.g., red
flour beetle, sawtoothed grain beetle, granary weevil, etc).

    Note: The American Malting Barley Association has a policy that does not allow for the use of any residual insecticide on malting barley. This would include the products malathion, and Reldan. These insecticides are allowable for use as residual bin sprays in bins that will be filled with malting barley. According to AMBA policy, the only chemical allowable for use on malting barley is phosphine (aluminum phosphide) fumigant to control an existing infestation.

    It is very important to note that in situations where grain drying is necessary, an insecticide protectant should be applied after the grain has gone through the drier. Commercial grain driers generate enough heat to rapidly degrade insecticides applied to grain prior to the drying process.

    6. In the fall, aerate to cool the crop and create a better storage environment in any bin larger than 2,000 to 3,000 bushel capacity. Determine if the aeration system in your bins will provide at least 1/10 cubic foot per minute (cfm) airflow for each bushel of crop being stored. Check the condition of the entire aeration system. You'll also need at least one square foot of opening in the bin for each 1000 cfm of airflow to allow the air to enter or exit from the bin. By gradually cooling
the stored grain through the fall, temperatures below 50EF should be achievable. At these temperatures, insect activity is reduced. The target temperature for stored grain should be 25EF for the winter. At this temperature, insect activity ceases and some mortality will occur for a number of our stored insect pests.

Phillip Glogoza
Extension Entomologist


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