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ISSUE 14  August 2, 2001

 

GRASSHOPPERS ON THE MOVE

There has not been much focus on grasshoppers this season. In Issue 7, a map summarizing grasshopper counts in field margins had most of the activity in the southcentral counties. That pattern has not changed much through the season. As small grains ripen, adult grasshoppers will move to late season crops to feed. Counties where growers should be more vigilant of migrating adults are Dickey, LaMoure, Stutsman, Foster, and Wells.

At this time of year, it is always important to monitor grasshopper movement to detect potential hot spots where adults have concentrated and to provide an early indication of problems for next year. If grasshoppers at the 8 per square yard level are observed, treatment should be considered. Another guideline would be defoliation levels. The magic reference point on defoliation for most crops is between 20 and 30%. Also, defoliation is often easier to assess than grasshoppers per square yard.

 

SOYBEAN APHID COULD BE ON THE MOVE

Word comes from Ian MacRae, entomologist at U of Minnesota-Crookston, that the soybean aphids in southeast MN are forming alates, or winged forms. When this occurs, the aphids will take flight in search of new, less crowded food resources. In light of the prevailing winds, which are from the southeast, this could foretell the first discovery of soybean aphid in our region.

With all the unwanted attention in soybean this season from caterpillars, many of you are scouting fields more aggressively than you normally would. Continue to be alert to finding soybean aphids in local fields. For more information, refer to Issue 2, May 10, of the Crop and Pest Report.

To look for soybean aphids, inspect the undersides of leaves in the top and middle of the plants, or the entire plant if you have time. If a yellow aphid is found on soybeans, there is a good chance you have found it. Record the number of plants infested and the relative abundance of aphids:

If you find aphids in soybeans, contact Phillip Glogoza at 701-231-7581 in North Dakota and Ken Ostlie, U of MN extension entomologist, at 612-624-7436 or Ian MacRae, U of MN extension entomologist-Crookston at 218-281-8611. Information requested is:

It is reported that this aphid feeds specifically on soybean (plants in the Genus Glycine). It is not expected that this aphid would feed on dry bean varieties (Phaseolus spp.). There are other aphids that may be found on dry beans, specifically the Bean aphid, Aphis fabae. This aphid is blue-black in color. The bean aphid has not been a problem in North Dakota but can be found when sampling dry bean fields.

 

CATERPILLAR ACTIVITY THIS WEEK

As before, continue to watch the same crops as mentioned in previous weeks. Several consultants in the central valley area have commented they are finding young thistle caterpillar larvae easily. Continue to watch their development. The Painted lady butterfly numbers peaked last week, so new egg laying should be winding down.

During field inspections around the valley, the alfalfa caterpillar and the cabbage looper have been the two most common found in soybean for the time being. Which are the most common in your particular area may vary. Soybean plants are growing well, and it will likely require the 8 caterpillars per row foot before significant impact will be observed.

 

PREPARATION OF GRAIN BINS AND PLANNING FOR LONG TERM STORAGE

It is time for the annual reminder. 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
pglogoza@ndsuext.nodak.edu


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