Minnesota Crop News

Anthony Hanson (hans4022@umn.edu), Extension Educator - Integrated Pest Management It's been a relatively slow alfalfa weevil season compared to previous years, though some reports of high population fields have trickled in during June. Most are mature larvae (i.e., fourth instar) that should cease feeding soon, but there are still some younger larvae present in samples (Fig. 1). Figure 1. Alfalfa weevil larvae collected from Morris, MN on June 17, 2025. Older third and fourth instar larvae are bright green, while first and second instars are smaller and pale yellow. Photo: Anthony Hanson.   While I've been finding larvae regularly in west-central MN, I haven't seen large enough populations that quite reach an economic threshold and financially justify a insecticide application. This has been the case this year across the state when I've checked in with other extension educators and crop professionals. I would not be surprised if there are scattered fields that have re...

Dr. Anthony Hanson,  Regional Extension Educator - Field Crops Integrated Pest Management Cold winters help prevent many potential pest insects from establishing in Minnesota or require species that cannot survive our winters to migrate up from southern states each year. Extreme cold can also knock back species that are established here. The cold can be a welcome event for farmers from a pest management perspective and has left many farmers wondering if 2025 will see a reduction in pest numbers, especially now that meteorological winter is over. The forecasts for the 2025 growing season are mixed depending on specific location within the state. Each year, I try to get a rough snapshot of how winter may have helped us out with reducing pest insect populations by using temperatures on the coldest night of the year. So far for most of the state, Jan. 21 had been the coldest night during winter 2024-25 with morning low air temperatures near -25 °F in the central portion of th...

In this episode of the Nutrient Management Podcast, our panelists discuss liming in detail. What kind of variation is there in liming recommendations? Since pH changes aren’t instant, when is the best time to apply limestone? Is lime application economically justified, and in what circumstances? What should growers know about selecting liming materials? What other bits of advice do our panelists recommend? TRANSCRIPT Guests: Daniel Kaiser, Extension nutrient management specialist (St. Paul) Carl Rosen, Extension nutrient management specialist (St. Paul) Jeff Vetsch, U of M researcher (Waseca) John Jones, Soil Fertility, plant nutrition, and nutrient management research, University of Illinois Urbana-Champaign Additional resources: Soil test pH and liming: Common questions and answers Lime needs in Minnesota Liming materials for Minnesota soils Fertilizer Recommendation Support Tool (FRST) — Click here to listen to all Nutrient Management Podcast episodes. For the latest nutrien...

Craig Sheaffer, Extension forage specialist, and Bruce Potter, Extension IPM specialist, and and Deborah Samac, Forage pathologist, USDA-ARS. This year’s above normal rainfall in June and July have had multiple direct and indirect effects on alfalfa forage yield and quality. On most soils there is adequate water for good forage growth, but untimely rainfall has had some detrimental effects. These include rain damage, windrow disease, and damage to alfalfa plants by insects and leaf disease. Problem 1: Rain damage Rained on hay and windrow disease. This year’s frequent rainfall events presented very narrow windows for harvest of alfalfa and other forage crops. It was often impossible to harvest alfalfa as hay when 3-4 drying days were required. Rainfall at any time after cutting results in losses of forage yield and quality. These losses are greatest for partially dried forages due to leaf loss. Average yield losses range from 20 to 30%, but can be as high as 100% if no hay is ha...

  Anthony Hanson (hans4022@umn.edu), Extension IPM Regional Educator - Field Crops Since the previous mid-May Minnesota Crop News post detailing tools available for 2024 alfalfa weevil management , multiple calls have come in showing just how difficult of a season this has been alfalfa growers dealing with this pest. The end of weevil season should be in sight for most growers possibly this week, though scouting should continue through June. Forecasting the timing of pest development (i.e., phenology) is a key tool for an integrated pest management (IPM) plan for alfalfa weevil. Temperature-based forecasts of alfalfa weevil development are based on degree-days for the eastern strain. As of June 13, 2024, at least according to the forecast model, larvae should cease feeding and develop into pupae across central Minnesota at 595 Fahrenheit alfalfa weevil degree-days (Fig. 1). Figure 1. Forecast alfalfa weevil development as of June 13, 2024 based on observed daily high and low tempe...

Anthony Hanson (hans4022@umn.edu), Extension IPM Regional Educator, and Bruce Potter, Extension IPM Specialist Mid-May to June is typically the time to begin scouting for insect problems in alfalfa. After our warm spring of 2024, alfalfa weevil adults, 1st stage larvae, and even a few 2nd stage larvae are beginning to be found in the southern half of the state (Fig. 1). Even if larvae are present in your fields, insecticide applications may not be needed if larval populations are not yield limiting or when alfalfa fields can be harvested soon. Cutting exposes the larvae to weather and can greatly reduce numbers. Figure 1. Alfalfa weevil larvae collected May 15, 2024 at the Southwest Research and Outreach Center by Lamberton, MN. Photo: Bruce Potter Farmers have been seeing a two-pronged challenge to managing alfalfa weevil in recent years: 1. An extended larval feeding season. 2. Reports of pyrethroids failures for alfalfa weevil. Each of these problems on their own have some solution...

Dr. Anthony Hanson,  Regional Extension Educator - Field Crops Integrated Pest Management Cold winters help prevent many potential pest insects from establishing in Minnesota or require species that cannot survive our winters to migrate up from southern states each year. Extreme cold can also knock back species that are established here. The cold can be a welcome event for farmers from a pest management perspective, but the record-warm winter has left many farmers wondering if 2024 will be a severe year for insects, especially now that meteorological winter is over. Each year, I try to get a rough snapshot of how winter may have helped us out with reducing pest insect populations by using temperatures on the coldest night of the year. So far for most of the state, Jan. 20 had been the coldest night during winter 2023-24 with morning low air temperatures near -15 °F in the central portion of the state and below -20 °F farther north (Fig. 1). NOAA and the US National Phenology Networ...