ISSUE 11 July 15, 2004
OUTLOOK FOR SOYBEAN APHID IS GOOD
As we enter the third week of July, we still have had no significant discoveries of soybean aphid reported for North Dakota. The news last week from Minnesota was similar, however there were some field detections in their statewide survey (see figure 1).
What is particularly interesting is the comparison of similar Minnesota survey information from previous seasons. Last year at this time, aphids were detected in fields all across the southern counties of Minnesota and as far north as Red Lake Falls (See figure 2).
Source: MN Pest Report, Vol. 4, Issue 6, July 9, 2004.
Even for North Dakota, by this time last year, our field surveys were detecting low levels of aphids as far north as Grand Forks County (see 2003 survey map)
Though we are no means beyond risk of soybean aphid infestations, the longer populations delay development, particularly to the south and east, it gets us to more advanced growth stages.
The observed trend for North Dakota from the past two seasons is that the population begins to increase significantly with aphid migration from soybean fields infested during July. Those more heavily infested fields have been to the south and east of North Dakota. Without large populations looming in Minnesota soybean fields, a significant migration and subsequent infestation are not as likely.
WHEAT MIDGE EMERGENCE UNDERWAY IN NORTHERN ND COUNTIES
Though populations have been low in most of the central counties, we have reached the point where midge emergence is underway throughout the east central counties and just beginning in the northern counties. Wheat fields where the crop is at a susceptible growth stage (boot to heading, and before 50% flowering), should be scouted to determine if midge are present at treatable levels. As a reminder, here are the treatment thresholds used for midge decisions:
Hard Red Spring Wheat
CORN BORER EMERGENCE IN CENTRAL ND
Degree days accumulated at about 20 to 25 per day this past week. Accumulations in the central counties, from east to west, have reached the point where moths are emerging and egg laying will begin. The wet weather of the eastern ND is not favorable for population increases. Scouting for eggs and larvae should begin by the week of July 19 to determine if populations warrant attention this year.
PREPARATION OF GRAIN BINS AND PLANNING FOR LONG TERM STORAGE
Small grain harvest is approaching and activities are underway to prepare storage bins for receiving new crop grain. Sanitation is an important program for preventing insect infestations from developing in these sites. It is also critical to be thinking about storage of grain and things necessary to keep insects and other storage problems to a minimum.
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 fumigant can be applied to control insects in the sub_floor area. It has NOT been approved for direct application to grain for many years. 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) to infest the new grain.
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, Reldan, 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, Reldan, Diacon II, or Storcide. 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, Reldan, or Storcide. 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.
For further information on stored grain handling, visit: