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Across Iowa, grain harvest is ramping up. A challenge this harvest season will be dealing with variable grain moistures from field to field as well as within individual fields. Additionally, drought conditions that have persisted all year and rapid accumulation of growing degree days are leading to grain that quickly became overly dry. Follow the below set of tips to limit yield loss this fall.
Decisions for phosphorus (P) and potassium (K) fertilization should consider slightly lower but still fluctuating crop and fertilizer prices compared with last year and very variable rainfall across the state. The current or expected crop and fertilizer prices after harvest and the yield level this harvest have a major impact on producers' fertilization decisions.
Soil-test P and K interpretations were updated last winter
While the registration of 2,4-D and dicamba products for over-the-top use in resistant-varieties has improved waterhemp control for many farmers, weed scientists warned that these herbicides would eventually select for resistant waterhemp populations. Bayer recently reported the discovery of two likely dicamba-resistant waterhemp populations in Iowa, which warrants a discussion on best management practices to slow the evolution of resistant waterhemp populations.
This is a great time of year to scout 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 slowed since the widespread introductions on non-crop acres in 2016. A new Palmer amaranth introduction was recently identified in a crop field in central Iowa, highlighting the importance for farmers and agribusiness professionals to remain vigilant in scouting for this species.
Since 2010, aphids have been colonizing corn later in the summer and can build up to surprising levels in Iowa. They can be found at the base of the stalk, around the ear and sometimes above the ear leaf. Aphids have been sighted in corn again this summer.
Aphids have been confirmed in corn fields for about two weeks, particularly in north central and northeastern Iowa. In some fields, the infestations are only along the edge rows, but in others, aphids may extend into the field interior. Spot checking fields for aphid activity is recommended as the growing season progresses.
Soybean aphids have been quiet the last few growing seasons in Iowa. This year there have been isolated fields in northern counties that exceeded the economic threshold, but most fields have not warranted insecticides. However, many scouting reports and our observations in northern Iowa counties for the last two weeks show soybean aphids are established. We strongly encourage sampling soybean now to gauge the pressure and make timely treatment decisions.
The Ag Container Recycling Council (ACRC) works with private and state contractors across the United States to collect and recycle 55-gallon or smaller containers. In 2022, over 900,000 pounds of pesticide containers were collected and recycled in Iowa.
When it comes to soybean, one of the most common types of injury is defoliation from insects. This damage can be easily detected in the canopy by observing holes in the leaves or along leaf margins as insects with chewing mouthparts consume leaf tissue. The insects most responsible for defoliation are bean leaf beetles, Japanese beetles, and grasshoppers. There are numerous caterpillars that also cause soybean defoliation, including green cloverworm, soybean looper and alfalfa caterpillar.
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. Development is driven by soil temperature and measured by growing degree days (GDDs). Research suggests about 50% of egg hatch occurs between 684-767 accumulated GDDs (since January 1; base 52°F, soil). Most areas within Iowa have reached peak egg hatch for corn rootworm (Figure 1), and we have heard several reports of folks finding larvae by digging roots in cornfields.
Japanese beetle development seems to be a bit ahead of schedule this year, much like other pests we track each spring. Japanese beetle adults begin emergence when approximately 1,030 growing degree days (GDD; base 50°F) have accumulated since January 1 and will continue emerging until 2,150 GDD have accumulated. Japanese beetle adults likely began emerging in the southern portion of the state last week, and emergence will likely occur within the next two weeks in northern Iowa (Figure 1).
