Integrated Crop Management News

Harvest is quickly approaching and most are anticipating a highly variable corn and soybean crop. Below are some reminders for regular maintenance, adjustments, and final checks to make sure your combine is ready to hit the fields soon.  

With delayed planting across the state in 2019, it is important to monitor crop development to determine unique grain drying needs this fall.

With delayed planting across the state, it is important to plan ahead for potential harvest challenges. Scout your fields for crop development to determine whether you might have potential problems with immature, frost-damaged grain, and wet grain.

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.

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.

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.

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).

Within the last week, I have heard about higher-than-normal stalk borer infestations along field margins compared to previous years. According to degree-day tracking of 2019, the caterpillars should be moving from overwintering hosts to corn throughout Iowa this week.

With the crops of Iowa in the ground, it is time to start thinking about seedling diseases. The Plant and Insect Diagnostic Clinic is a resource for corn and soybean growers assessing their field  throughout the season.

It’s been a wait-go-stop (repeat) corn planting season this spring. Whether you planted early or are just now getting corn planted, it seems planting windows were short and rushed. In some cases this meant planting (corn/soybean) and worrying later about getting nitrogen (N) applied. And in some areas of Iowa, wetter than normal conditions are raising questions about supplemental N application. What are the options for sidedress N?

Wet springtime conditions typically raise questions about the status of applied nitrogen (N). Or the question, do I need to apply additional N to my cornfields? At this time we do not know what the weather/precipitation will be for the entire springtime, but the extended period of wet conditions this spring is of concern.

Whether it's too much rain or perfectly timed rain, many fields are flooded or too wet to continue planting in many parts of Iowa. Delayed and preventative planting crop insurance dates are fast approaching with an unfavorable weather forecast. Decisions surrounding your delayed and prevented planting provision need to involve a conversation with your crop insurance provider.

Earlier this spring, we discussed using the PEAQ method (Predictive Equations for Alfalfa Quality) to help determine when to harvest first crop alfalfa. Looking at the PEAQ measurements made around the state, we are getting close to taking the first crop alfalfa. However, the wet conditions could present some challenges with putting up the first cutting of alfalfa in a timely fashion and maintaining feed quality.

Whether it's too much rain or perfectly timed rain, many fields are flooded or too wet to continue planting in many parts of Iowa. Delayed and preventative planting crop insurance dates are fast approaching with an unfavorable weather forecast. Decisions surrounding your delayed and prevented planting provision need to involve a conversation with your crop insurance provider.