Minnesota Crop News

by Jodi DeJong-Hughes, Extension educator
In Minnesota, small grain harvest is complete and sugar beet, sweet corn, corn silage, and pea harvest is well underway. With these early harvested crops, producers have an opportunity to consider planting a cover crop this fall, a practice that has many benefits. This may be a particularly good year to try cover crops, since soil moisture in many parts of the region is ideal for germination.

By Jeff Coulter, Extension Corn Specialist
Much of the corn in Minnesota is in the dent stage of kernel development. At this time, stress to corn from dry conditions can impact yield by reducing kernel size.

To evaluate the impact of this season’s weather on corn yield potential and its spatial variability across the Corn Belt, including three locations in Minnesota, yield forecasts were made on August 24 by University of Nebraska researchers as part of a multi-state project. Statewide forecasts of corn yield also were developed. Updated forecasts are planned for early September.

by Robert Koch (Extension Entomologist) and Daniela Pezzini (Graduate Student)

The brown marmorated stink bug (BMSB) was recently detected for the first time in Minnesota soybean. A single adult specimen was collected in sweep net samples from a soybean field in Dakota County on August 17, 2016. Follow-up sampling of that same field performed on August 25, 2016 did not detect any additional BMSB. This invasive pest of Asian origin uses piercing-sucking mouth parts to feed on developing soybean pods and seeds. In more easterly states, this insect has caused significant yield losses to soybean and other crops. In Minnesota, we are unaware of any fields with densities of stink bugs near treatable levels; therefore, we do not envision any insecticide treatments being needed for this pest at this time. The intent of this article is to alert you to the presence of this new invader, which could become a threat to Minnesota crops in the near future. Further information on BMSB and other sti…

Jodi DeJong-Hughes, Extension educator - crops
Compaction is often thought of as a spring problem. However, in seven of the past 10 years, parts of Minnesota have had wet soil conditions during harvest.

What should a producer do when the soil is wet and harvest needs to be completed? Should producers risk significant compaction and harvest the crop or just stay off of the field? The answer is easy: harvest the crop.

Lisa Behnken, Fritz Breitenbach, Jeff Gunsolus, Phyllis Bongard, Liz Stahl

Photo 1. Palmer amaranth in a Tennessee field. Source: Lisa Behnken Palmer amaranth is not native to the northern US, but has spread northward from southern states, being confirmed in Wisconsin, Iowa, Illinois and Nebraska (2011–2013), South Dakota (2014) and other northern states. In 2016, it was discovered in newly-seeded CRP land in Iowa, including Clayton County, just one county away from southeastern Minnesota.

Bruce Potter, (Extension IPM Specialist) and Robert Koch (Extension Entomologist)

Soybean aphids and other insect pests are able to reduce soybean yield until the R6.5 stage (yellow pods begin) stage. You want to pay some attention to soybean insect problems (and identify weed and disease issues) until then. However, this year's aphid scouting efforts should increasingly focus on fields with less mature beans. As the 2016 soybean aphid season begins to wind down, there are several aspects of late-season soybean aphid populations that can influence insecticide decisions.

by Jeff Coulter, Extension Corn Specialist
Much of the corn in Minnesota is in the dough stage of kernel development. Once kernels enter the dough stage, about four weeks after tassel emergence, kernel number is established and yield loss caused by stress is due to a reduction in kernel size.

by Robert Koch (Extension Entomologist)
Insecticides are an important tool in the IPM toolbox for protecting crop yields from pests. However, we need to keep in mind that many of the insecticides we use to manage crop pests are also toxic to beneficial insects, such as predators and pollinators. This article will provide an overview of some considerations for reducing the risk of impacting pollinators (e.g., bees and some flies) when foliar insecticide applications are made to crops.

by Robert Koch (Extension Entomologist) and Bruce Potter (IPM Specialist)
Growers now have access to two more miticides for use against twospotted spider mites in soybean. These miticides are Agri-Mek SC (Syngenta) and Zeal SC (Valent). These are welcomed additions to the limited suite of chemicals for management of twospotted spider mites in soybean.  They represent insecticide groups (modes of action) not used for soybean aphid.

by Robert Koch (Extension Entomologist) and Bruce Potter (IPM Specialist)

History has shown us many times that over-reliance on pesticides often results in development of pesticide resistance in pests. Last summer in parts of southern Minnesota, some pyrethroid insecticides (bifenthrin [e.g., Brigade, Tundra , Hero and others] and lambda-cyhalothrin [e.g., Warrior and others]) failed to provide adequate control of soybean aphid. Historically, these have been among the top performing pyrethroid insecticides for soybean aphid management. Follow-up laboratory bioassays confirmed resistance  (10- to 44-fold resistance) to these insecticides in a soybean aphid population collected near Lamberton, MN. The majority of these performance issues in 2015 appeared centered in and near Brown, Redwood and Renville counties. In most other areas, pyrethroid insecticides preformed as expected and effectively suppressed aphid populations.  Here, we provide updates on resistance monitoring for 20…

by Jeff Coulter, Extension Corn Specialist
Much of the corn in Minnesota has finished pollinating and kernels are in the blister to milk stage. Kernels enter the blister stage at about 12 days after tassel emergence and the milk stage at about 20 days after tassel emergence. Stress to corn during the blister and milk stages from dry and/or hot conditions can diminish grain yield, primarily by reducing the number of kernels per plant.