This is the time of year to begin scouting for Palmer amaranth (Amaranthus palmeri) in Iowa crop fields. While Palmer amaranth has been identified in more than half of Iowa’s counties, new identifications have waned since the widespread introductions in 2016. Palmer amaranth is still a species to watch out for in every Iowa crop field. Minnesota recently reported finding the weed in a county previously not known to have infestations – thus the weed is still on the move.
Integrated Crop Management News
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Most people are probably aware of the unsolicited mailing of seed packets from China and other countries. The Iowa Department of Agriculture and Land Stewardship (IDALS) has issued guidelines on how to deal with the situation if you should receive one of these packages. The following statement was made by IDALS.
Why do we care?
Late summer can provide a window of opportunity to seed perennial forage legumes and grasses, whether you want to establish a new forage crop or need to fill in bare and thin spots in an existing forage stand. To help improve the chances for a successful late summer seeding of forages, consider the following.
Field preparation prior to seeding
As parts of Iowa enter severe drought on July 14 (D2, US Drought Monitor), I encourage you to scout for twospotted spider mites in crops. Twospotted spider mites can increase whenever temperatures are greater than 85°F, humidity is less than 90 percent, and moisture levels are low. These are ideal conditions for the twospotted spider mite and populations are capable of increasing very rapidly.
This year we have received many inquiries about potato leafhopper (Photo 1) in soybean and alfalfa. Although they are present in Iowa every year, populations are higher than in 2018 and 2019. Usually, potato leafhoppers are only considered a pest of alfalfa in Iowa, but they do feed on soybean, too. Potato leafhoppers prefer smooth leaves and are usually repelled by varieties with pubescence (hairs).
An ongoing public concern is the loss of nutrients from agricultural land in the corn belt. In Iowa, nitrogen and phosphorus losses from farm fields are driven by a variety of factors. Since the mid-twentieth century, statewide corn and soybean acres have increased as extended rotations, hay, and pasture declined. Compared to perennial crops and small grain rotations, corn-soybean and continuous corn rotations are leaky systems.
The Ag Container Recycling Council (ACRC) sponsors a free program to recycle clean triple-rinsed or pressure-rinsed pesticide containers up to 55 gallons in size. Refer to the ACRC Container Preparation Checklist for more information on preparing containers. Under the ACRC program, G. Phillips and Sons, LLC, located in Stanwood, IA collects and recycles containers in Iowa.
Soybean gall midge was confirmed as an economic pest of soybean in 2018. Worldwide, it is only known to occur in five states in the Midwestern US (Figure 1). Research began in 2019 to monitor the emergence of adults and incidence of larval feeding, as well as management options for the pest. This year, soybean gall midge adults were first collected on June 12 and larvae were detected in soybean on June 23.
Farmers have enjoyed the benefits of Bt corn since its introduction in 1996, particularly “in the bag” transgenic protection from insect pests and the yield loss they inflict. European corn borer (ECB), Ostrinia nubilalis, was particularly challenging and the target of the first Bt hybrids. The adoption of Bt corn in the U.S. prompted a widespread suppression of ECB. Even so, ECB still shows up in conventional cornfields in Iowa and can be a devastating pest.
Several Iowa State University Extension and Outreach Field Agronomists have reported fields with high numbers of grubs this spring. There are a number of grub species in Iowa, including Japanese beetle. With warm temperatures accelerating insect development, expect adult Japanese beetles to begin emergence in southern Iowa counties this weekend (Figure 1). The emergence is about 7-10 days ahead of the last few years. Literature shows Japanese beetle adults need about 1,030 growing degree days (base 50°F) to complete development and will continue emergence until around 2,150 degree days.