In 2019, numerous field edges were infested with common stalk borer. Tracking degree days is a useful tool to estimate when common stalk borer larvae begin moving into cornfields from their overwintering hosts. Foliar insecticide applications, if needed, are only effective when larvae are migrating and exposed to the insecticide. Start scouting corn for larvae when 1,300-1,400 degree days (base 41°F) have accumulated. Much of Iowa has reached this important benchmark (Figure 1), and therefore scouting for migrating larvae should begin now to make timely treatment decisions.
Integrated Crop Management News
Links to these articles are strongly encouraged. Articles may be republished without further permission if published as written and if credit is given to the author, Integrated Crop Management News, and Iowa State University Extension and Outreach. If articles are used in any other manner, permission from the author is required.
Iowa State University (ISU) research has evaluated corn and soybean response to preplant potassium (K) fertilizer placement methods and starter since the middle 1990s. These results have been used for developing guidelines in Extension publication PM 1688. In recent years, excessive fall and spring rainfall sometimes has precluded the normal K preplant fertilization. Therefore, growers and crop consultants have been asking if sidedressed liquid K fertilizer could alleviate deficiency or be a good complement to preplant K fertilization, as is commonly the case for nitrogen.
With planting wrapping up and crops beginning to emerge, now is the time to start scouting fields regularly throughout the growing season for any potential issues. Scouting fields and monitoring crops throughout the growing season can help you make more informed management decisions and stay on top of potential issues that may come up during the growing season. Even if some issues cannot be fixed, regular scouting can help us better understand what happened in the field and make adjustments to reduce issues in the future.
Every spring, alfalfa growth and development differs due to variations in climatic, variety, stand age and other crop production factors. With the 2020 growing season being off to a cooler than normal start, alfalfa growth is also off to a slower start this spring. This is a good reminder that while calendar date is one method used to determine when to harvest first crop alfalfa, it is not the best method to use. Instead, the PEAQ method (Predictive Equations for Alfalfa Quality) developed by the University of Wisconsin does a better job.
Black cutworm (BCW) is a migratory pest that arrives in Iowa with spring storms each year. BCW moths lay eggs in and near crop fields, and larvae can cut corn seedlings or feed on leaves. Even though crops were planted earlier this year than previous years, cold temperatures may slow growth and allow BCW larvae to coincide with early vegetative corn that is vulnerable to BCW injury.
Adult alfalfa weevils become active and start laying eggs as soon as temperatures exceed 48°F. Like other insects, the development of alfalfa weevil depends on temperature and we can rely on the accumulation of growing degree days (GDD) to predict activity. Alfalfa weevil egg hatching begins when 200-300 degree days have accumulated since January 1.
Pesticide applicators and handlers need to wear, at a minimum, the Personal Protective Equipment (PPE) specified on pesticide product labels. Most pesticide labels require a long-sleeved shirt and long pants. Proper laundering of work clothes that may be contaminated with pesticide residues is essential to reduce pesticide handlers’ short- and long-term exposure to pesticides and prevent the potential of residue cross-contamination onto other clothing.
Bean leaf beetle adults (Photo 1) are susceptible to cold weather and most die when air temperatures fall below 14°F (-10°C). However, they have adapted to winter by protecting themselves under plant debris and loose soil. Each spring, adult beetles emerge from their overwintering habitat and migrate to available hosts, such as alfalfa, tick trefoil, and various clovers. As the season progresses, bean leaf beetles move to soybean and other hosts. While adult activity can begin before soybean emergence, peak abundance often coincides with early-vegetative soybean.
The weather this year has been quite variable – several warm days followed by a cold, snowy week in April is just one example of the dramatic changes we’ve experienced in air temperatures (Figure 1). Each winter, we receive the question “Will insect pests be worse/better this year?”, and cold snaps during the spring cause people to wonder “Do fluctuating temperatures affect pest populations?” The short answer to these questions: it depends, but probably not.
Over the past two decades, scientists and beekeepers alike observed drastic declines in bee populations. On average, beekeepers lose significantly more honey bee colonies each year and fewer native bee species are spotted in the wild. This is especially apparent in the Midwest where research conducted at Iowa State University observes multiple factors that contribute to the decline in bees and other pollinators. According to an annual Bee Informed Partnership survey, Iowa beekeepers typically lose between 40-60% of their hives each year.