MSU Extension Cass County

Late-season warmth helps with corn maturity

The 2018 spring planting season was marked by lengthy delays due to persistent periods of wet weather. While the moisture received in the spring was very beneficial, as the weather turned dry across most of Michigan in July, planting delays caused headaches for producers that spent most of the season playing catch up with crops in very different stages of growth.

As the calendar switched from May to June, many planned corn fields were still left unplanted. Soon after, the switch was on from planting corn to soybeans. While most of the area’s fields were planted by June 15, there were still surprising numbers of acres that had not been planted until conditions dried out in the third week of June.

While it is unclear when the first killing frost will occur in southwest Michigan this year, it is a sure bet that the much warmer than normal temperatures we have seen in September, along with a return to favorable rainfall, have helped the crops greatly.

The BE GDD system does not count temperatures above 86 degrees Fahrenheit as providing additional corn growth potential. This suggests that 100 RM corn planted by May 31 should be at or close to black layer by Sept. 18, 2018. Corn planted in June may still have a ways to go to reach physiological maturity. The current 6-10 and 8-14 day outlooks are calling for a return to more normal to cooler than normal weather for the period.

Corn at physiological maturity can be anywhere from 28-35 percent moisture, depending on a combination of factors, including hybrid characteristics such as husk leaf number and tightness, relative humidity, temperature and wind. Drying of corn grain occurs much faster during extended periods of hot and dry conditions. It takes approximately 30 GDDs to remove 1 percent of moisture in corn grain. Early planted corn had the opportunity to be exposed to 10 days of 25 GDD or warmer temperatures since reaching physiological maturity. Robert Nielsen, Purdue University corn agronomist, has written an excellent resource, “Field Drydown of Mature Corn Grain,” which discusses this process more fully.

Field research to study control measures for Asiatic Garden Beetles in 2017-18

Last year, it was reported that MSU Extension had seen a resurgence of a field corn pest known as Asiatic Garden Beetles. The damaging life cycle stage of this pest is the larvae, which are white grubs. They feed on corn roots, causing stunted plants, population and yield loss. The adults of this pest seemed to be particularly attracted to marestail, a weed species that has become very widespread and problematic in our area because of its resistance to glyphosate (Roundup), one of the most commonly used herbicides in soybean production. It is thought that marestail is particularly useful to the pest because the plant can germinate in either the spring or the fall, it’s roots providing a food source for the larvae into late fall, before it migrates below the frost line to overwinter in the soil. Soybean fields with high levels of marestail that are rotated to corn are particularly prone to damage from this pest. In 2018, MSU Field Crops Entomologist Dr. Chris DiFonzo, with funding provided by the Michigan Corn Growers, established several research plots across Michigan to study the best ways to avoid damage from the pest. Soil insecticides were applied in combination with seed treatments to evaluate effectiveness of control. This research is on-going, and yield data will be collected in late fall 2018.

Soybean Sudden Death Syndrome (SDS)

Symptoms of SDS became visible in southwest Michigan fields in Spring 2018. Wet feet in soybean plants in early spring often increase the chance for root rots. This spring’s prolonged wet conditions in May and June set the stage for SDS infection. Up until recently, MSU Extension has not seen substantial visual symptoms of the disease. However, the telltale yellow spots and yellowed areas with brown necrosis in soybean leaves were visible in infected areas in fields this year. There is no rescue treatment for the disease, only the opportunity to keep good field notes so that growers can select partially resistant varieties in future years when soybeans are being raised on the field again. It is also important to note that the disease can be spread by movement of soil from infected fields through tillage equipment, or other means. Farmers should power wash equipment as it comes out of fields to reduce the potential spread.