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Many areas of Minnesota and Northern Iowa are currently experiencing a fairly dry weather pattern. Since mid-June, most rainfall events across the region have been quite spotty in coverage, and most locations that were fortunate enough to receive rainfall have measured only a tenth or two up to one-half inch, with some isolated areas getting higher rainfall amounts. Even a small amount of rainfall has been very beneficial, especially those areas that received one-half inch or greater rainfall. Fortunately, stored soil moisture amounts were above normal in most areas as we entered early July, which has helped maintain crop development, especially on the heavier soil types. Another weather benefit during the early portion of July has been near-normal temperatures, with only a few very hot days, which has helped slow crop deterioration from the drier weather pattern. However, there have been signs of crop stress in recent days on some lighter, sandier soils at some locations. Forecasts call for increased temperatures and limited rainfall in the next week to ten days, which could result in more significant crop deterioration in areas that are most in need of rainfall.

Most corn in Southern Minnesota and Northern Iowa will be reaching the very important tasseling and pollination stage in the next two weeks. This period is very critical for determining final yield potential for the 2008 corn crop. Any corn that is under significant moisture or heat stress during this period will likely have reduced yield potential. The negative impact on the corn is greatest on the light, sandy soil types, and areas with a shallow root system due the heavy rains in early June; however, even corn on heavier soils can be significantly impacted during extended periods of extreme heat and very little rainfall. Some rainfall is needed in many areas during the next couple of weeks in order to assure proper ear fill and kernel development to achieve the yield potential that has been established. This period is also a critical time for soybean development, as they are in the blossom stage, and will begin setting pods very shortly. Crop development in most areas has made raid development in last 2-3 weeks due to some warmer temperatures; however, the accumulation of growing degree units (GDU’s) since May 1 across the region is running 7-15% behind normal. One positive of the warm, dry weather has been a slowdown in the development of soybean aphids. So far, aphids are being reported in soybean fields across Southern Minnesota, but for the most part they have been well below the threshold levels for insecticide treatment. Costs to treat for soybean aphids would likely be about $12-18/acre.