ISSUE 17 September 28, 2001
SOYBEAN APHIDS IN EASTERN ND COUNTIES
Soybean aphid were first detected on soybean in North Dakota on August 17, in Cass County. Since that time aphids have been found in additional counties in other eastern counties. The map provides an overview of those counties where aphids have been found or reported.
In late August, the aphids were present in very low numbers, generally one or two nymphs on an infested leaf. These nymphs were small, appearing as a small yellow spot on a leaf. The infestation was the result of a winged female landing, bearing one or two live nymphs, then moving to another plant. The same type of pattern was found in Foster county in mid-September.
In the eastern counties indicated on the map, small colonies of aphids were found on the undersides of lower leaves. The best place to locate aphids had been field margins on green plants that were isolated from others.
Soybean aphid did not cause any problems with this years crop. The arrival was late and the numbers were low. It does mean that next year we are likely to see soybean aphid much earlier in the season due to the likelihood of overwintering in the region.
For more information on soybean aphid, visit the NDSU Extension Service web pages for insect updates at:
GRASSHOPPER OUTLOOK FOR NEXT SEASON
During fall field activities it is a good idea to assess adult grasshopper populations for gaining some insight into next years outlook. When adult grasshoppers number 8 or more per square yard, the egg production by females is adequate to produce threatening numbers of nymphs the following spring. In these areas, early scouting during hatching is recommended in order to locate those areas along field margins, fence lines, or other fall egg laying sites that require treatment, long before grasshoppers grow and move into field crops.
This past season, the NDSU IPM Small Grain survey scouts monitored grasshopper populations in field margins. The map summarizes their observations of grasshopper nymphs from June to the end of July. The one area of the state where grasshopper nymphs numbered around the threatening level was in the south central region. Producers in these areas should observe adult grasshoppers closely to locate next seasonís high risk fields. A threatening level of grasshopper nymphs in field margins is 50 or more per square yard. Threatening levels within a field is when 30 or more per square yard are found.