Given the dry conditions that prevailed Iowa in 2023, there will be herbicide carryover in 2024. Suspect herbicides that are likely to carryover include, but are not limited to atrazine, clopyralid, and the various HPPD inhibitor herbicides. Specifically, the accuracy, evenness, and timing (i.e., later in the season) of the 2023 herbicide applications can increase the potential for interactions with the 2024 herbicides.
As mentioned in my previous ICM Blog article this year, June 20 was the cut-off date for over-the-top applications of dicamba products (Xtendimax, Engenia, and Tavium) in dicamba-tolerant soybean in Iowa. This was an amendment to the federal cut-off date of June 30.
Did an earlier cut-off date mitigate the problem in 2022?
This spring's weather has resulted in an unusually slow start to the growing season, especially when compared with the past two years. In springs like these, field operations are condensed and there may be temptation to skip some of the field preparation to get acres planted in a timely manner. This article will address considerations for herbicide applications in these situations.
As we continue the postemerge herbicide applications for corn and begin this process for soybeans, it’s important to be on the lookout for temperature inversions, Photo 1. This blog will discuss what temperature inversions are, why they can be dangerous for pesticide applications, and how to identify when temperature inversions are happening. It is never recommended to spray a pesticide when a temperature inversion exists, and many labels provide guidelines to follow in order to avoid applications during one.
Multiflora rose (MFR) is a common weed in pastures, CRP, timber and other areas that are not annually disturbed. Now is an appropriate time for treatment of these weeds in pastures and other areas they invade.
Performance of preemergence herbicides in many areas of the state may be less effective than normal due to limited rain following application. Although weed emergence following planting was reduced by dry soils and cool temperatures, it is likely that most fields will have some weeds that emerged during this period. Systematic scouting of fields, beginning shortly after crop emergence, will be essential to determine how best to manage weeds throughout the remainder of the season
The 2020 registration for Xtendimax, Engenia and the extension of the Tavium registration included additional restrictions for protection of Endangered Species.
Iowa counties with Endangered Species protection include Allamakee, Cerro Gordo, Clayton, Delaware, Dickinson, Dubuque, Emmet, Hancock, Howard, Jackson, Kossuth and Osceola.
Marestail is one of the most widespread and troublesome weeds in Iowa croplands. It can grow to a height of 1.5 to 6 feet, produce up to 200,000 seeds, and can reduce soybean yields up to 80% if not controlled (Figure 1). Marestail seeds are light and disperse across landscapes with winds. Seeds have little dormancy and can germinate soon after seed shed. In general, 75% of seedlings germinate in fall, remain in rosette-stage until spring, begin stem elongation in April, and start flowering in July. About 25% of seeds germinate in the spring.
The following is a brief summary of new products available for weed control in corn and soybean in 2021. None of these are new sites of action herbicides, but are new premixes or revised formulations of existing active ingredients.
Waterhemp is a dioecious (male and female flowers on separate plants) pigweed with a high genetic diversity. Consequently, this pigweed has a high propensity to adapt to control tactics and has evolved resistance to herbicides from as many as 6 or 7 different herbicide groups (HGs). Out of 75 waterhemp populations collected from corn/soybean fields in Iowa in fall 2019, almost 25% had a four-way multiple resistance to HGs 2 (ALS inhibitors), 5 (atrazine), 9 (glyphosate), and 14 (PPO inhibitors).
