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.
WHEAT MIDGE UPDATE
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.
PREPARATION OF GRAIN BINS AND PLANNING FOR LONG TERM STORAGE
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).