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. In 2019, the average hatching date will be behind the average, due to cool spring temperatures. Development is driven by soil temperature and measured by growing degree days. Research suggests about 50% of egg hatch occurs between 684-767 accumulated degree days (base 52°F, soil). Most areas in Iowa have reached peak corn rootworm egg hatch (Fig. 1).
Integrated Crop Management News
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Within the last week, I have heard about higher-than-normal stalk borer infestations along field margins compared to previous years. According to degree-day tracking of 2019, the caterpillars should be moving from overwintering hosts to corn throughout Iowa this week.
Several reports from ISU Field Agronomists have indicated Japanese beetles are emerging in southern Iowa. The emergence is about 7-10 days behind the last few years, due to slowly accumulating degree days in 2019. 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. Based on accumulating degree-day temperatures in 2019, Japanese beetle adults should be active in some areas of southern Iowa this week (Figure 1).
Last year, the widespread outbreak of soybean gall midge took many farmers and entomologists by surprise. There was significant field edge injury and economic loss in at least 65 counties in Iowa, Nebraska, Minnesota, and South Dakota. A small team organized a concerted effort to learn more about the life cycle, biology and management of soybean gall midge in 2019. The first step was to establish emergence cages in various habitat types to better understand where they overwinter.
With the crops of Iowa in the ground, it is time to start thinking about seedling diseases. The Plant and Insect Diagnostic Clinic is a resource for corn and soybean growers assessing their field throughout the season.
Making a diagnosis
The first step in managing a plant problem is to know what is causing the symptoms observed. Accurate pathogen or insect pest identification is one of the most important integrated pest management (IPM) tactics leading to a successful management strategy.
While good progress has been made toward getting crops in the ground, the adverse early spring conditions are likely to complicate weed management throughout the 2019 growing season. The most important step in minimizing problems is to scout fields regularly to identify problems quickly and allow timely adjustments to management.
It’s been a wait-go-stop (repeat) corn planting season this spring. Whether you planted early or are just now getting corn planted, it seems planting windows were short and rushed. In some cases this meant planting (corn/soybean) and worrying later about getting nitrogen (N) applied. And in some areas of Iowa, wetter than normal conditions are raising questions about supplemental N application. What are the options for sidedress N?
It’s time to turn thoughts towards nematodes that feed on corn! It is very common for Iowa corn fields to have several different species of plant-parasitic nematodes present at low numbers. It’s only when numbers are present at damaging levels that symptoms of injury will appear. This article discusses when and how to sample for plant-parasitic nematodes that can damage corn.
Wet springtime conditions typically raise questions about the status of applied nitrogen (N). Or the question, do I need to apply additional N to my cornfields? At this time we do not know what the weather/precipitation will be for the entire springtime, but the extended period of wet conditions this spring is of concern.
Whether it's too much rain or perfectly timed rain, many fields are flooded or too wet to continue planting in many parts of Iowa. Delayed and preventative planting crop insurance dates are fast approaching with an unfavorable weather forecast. Decisions surrounding your delayed and prevented planting provision need to involve a conversation with your crop insurance provider. There is a nice article available on the Ag Decision Maker website that talks about the insurance provision implications.