While there is significant uncertainty about this year’s harvest weather, the struggles with previous year soil compaction may still be lurking in corn and soybean fields across Iowa. This article will highlight challenges with wet conditions at harvest and opportunities to minimize the long-term consequences of harvesting fields with wet soils.
Integrated Crop Management News
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Increasing demand to use corn plant biomass for producing energy and various products has spurred interest in harvesting corn stover and specific plant components in addition to grain. Harvesting more biomass means increased carbon (C) and other nutrient removal from fields. What is the nutrient removal when different corn plant components are harvested?
Problems caused by unfavorable conditions this season have resulted in greater than normal weed escapes. These weeds may reduce crop yields and definitely will contribute to future weed problems via new seed. While it is too late to protect crop yields, a common question is whether herbicides can be used to reduce the quantity of viable weed seed produced by weeds. While there is no simple answer due to the many different scenarios across the state, in most situations late-season applications are not warranted.
Since early August, soybean in several fields began showing typical potassium (K) deficiency symptoms on leaves located in the middle to upper canopy. This is not surprising in fields or portions of fields with soil-test values in the very low or low K soil-test interpretation categories that did not receive adequate preplant K fertilization. Potassium deficiency symptoms are well-known and very common in older leaves during early growth stages.
Now is a great time to scout for Palmer amaranth (Amaranthus palmeri) in Iowa crop fields. As of late 2018, this species had been identified in over half of Iowa’s 99 counties. While new identifications have waned since the widespread introductions in 2016, Palmer amaranth is a species to watch out for in virtually any Iowa crop field.
Western and northern corn rootworm are major corn pests in Iowa and surrounding states (Photos 1 and 2). Farmers have seen several management changes, including the release of four Bt-rootworm traits to suppress corn rootworm larvae since 2003. Although both species are persistent pests, western corn rootworm is particularly adaptable. The Gassmann Lab at Iowa State University (ISU) has confirmed western corn rootworm resistance to all Bt rootworm traits in Iowa.
There have been some reports of potato leafhopper activity and plant injury in Iowa alfalfa this season. Some fields experienced winter injury and the cooler spring provided a slow start to plant growth in 2019. It is time to think about assessing alfalfa stands. Potato leafhoppers (Photo 1) do not overwinter in Iowa, but they are persistent alfalfa pests every growing season. Storms along the Gulf of Mexico bring adult potato leafhoppers north and drop them into fields every spring.
Those looking for any piece of good news in all of the rain-soaked suffering that has occurred in 2019 have asked “Will all this rain and flooding drown SCN”? Unfortunately, the answer is “no.” The reasons why are explained. And a small bit of good news about the wet growing season and SCN is offered up in this article as well.
In-season plant tissue testing can be useful in diagnosing nutrient deficiencies in field crops, but it must be used with caution. Extra care is needed this year given the unusual crop planting and growing conditions.
Corn rootworm egg hatch in Iowa typically occurs from late May to the middle of June, with an average peak hatching date of June 6 in central Iowa. In 2019, the average hatching date will be behind the average, due to cool spring temperatures. Development is driven by soil temperature and measured by growing degree days. Research suggests about 50% of egg hatch occurs between 684-767 accumulated degree days (base 52°F, soil). Most areas in Iowa have reached peak corn rootworm egg hatch (Fig. 1).