Seedcorn Maggot Activity Beginning in Southern Iowa

Apr 13, 2023

By Ashley Dean and Erin Hodgson

Seedcorn maggot larvae feed on germinating seeds or seedlings of corn and soybean (Photo 1). Feeding can delay development or kill the plant, and plant injury is especially prevalent during cool, wet springs when plants grow slowly. Even with variable weather so far this spring, seedcorn maggot development is on track with previous years. Forecasted temperatures suggest that seedcorn maggot will likely develop quickly in the next few weeks. Farmers thinking about planting should track growing degree days to reduce the risk of injury in high-risk fields, which include those with a history of seedcorn maggot injury, recently tilled fields, and fields where organic matter was recently incorporated (e.g., manure or cover crops).

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Photo 1. Seedcorn maggot on soybean. Photo by University of Minnesota Extension.

Seedcorn maggot has a lower developmental threshold of 39°F and an upper threshold of 84°F. Peak adult emergence for the first generation occurs at 360 accumulated degree days (GDD) since January 1. Based on current GDD, the first generation of adult seedcorn maggot has likely emerged throughout much of southern Iowa (Figure 1).

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Figure 1. Accumulated growing degree days (base 39°F) in Iowa from January 1 to April 9, 2023. Map courtesy of the Iowa Environmental Mesonet, Iowa State University Department of Agronomy.

It is recommended to avoid planting during peak adult emergence, because first-generation larvae typically emerge within a few days (414 GDD) and feed for several weeks (781 GDD). Remember that cool soil temperatures likely increase the risk of seedcorn maggot injury because seeds take longer to develop; warmer soil temperatures may be conducive to quick growth of seedlings and less injury. If possible, target planting during the “fly-free” period (781-1,051 GDD) in areas at higher risk for seedcorn maggot.

You can track GDD for seedcorn maggot by visiting the Pest Maps and Forecasting page and comparing key GDD to the map. Additionally, if you choose your nearest weather station on the right side of the page, you can see forecasted GDD for the next two weeks.

While no rescue treatments are available, cultural and chemical methods prior to or at planting can minimize risks. Read more about seedcorn maggot biology, risk factors, and management in this encyclopedia article. To confirm seedcorn maggot injury, check areas with stand loss and look for maggots, pupae, and damaged seeds (hollowed out seeds or poorly developing seedlings), and keep an eye out for other seedling pests, such as wireworms or grubs.

Source : iastate.edu

Video: Western Canadian Agriculture: Hard Times Made the World's Best Farmers

Western Canadian agriculture produced the most advanced farmers in the world not through abundance but through adversity. The crow rate fell. The wheat price went nowhere. The brown envelopes stopped.

When the subsidies disappeared, the bad farmers left and the good ones stayed. And the ones who stayed could not just grow wheat anymore. They started growing lentils and canola and peas and flax and faba beans. They built crop rotation. They got serious about agronomy because there was no government backstop. That process produced the Western Canadian agriculture Dennis Bulani describes in this clip: the most advanced, most educated farming culture in the world.

His contrast with Iowa corn and soybean farmers is sharp. At a DeKalb farmer meeting in Okoboji, Iowa, he asked what crop rotation they ran. Beans on corn stubble, corn on bean stubble. How do you fertilize? The co-op agronomist handles it. Have you considered other crops? No need. We make so much money on corn and soybeans. Western Canadian agriculture was never allowed that comfort. And now those Iowa farmers are watching soybean markets lock up with China and corn prices slide, and they do not have the agronomy knowledge or the research base to pivot. Western Canadian farmers adapted on a dime because they had done it before.

Dennis also makes the case that Western Canadian agriculture keeps adapting in real time. Low commodity prices over the past year have pushed growers to look seriously at precision spot-spray technology. He knows a neighbor who bought a sprayer with the seeing-eye system and sprayed only 80 out of 320 acres. As a chemical retailer Dennis acknowledges that will affect his sales. He supports it anyway, because if it advances Canadian agriculture and makes farmers money, that is a good outcome.

The lesson Dennis draws from the tale of two farms: continuous improvement is the only durable strategy. When canola was $22 a bushel some growers went to Arizona instead of the Crop Production Show. When the price came down those same growers came back to the research and the discipline. Products do not go on Rack Petroleum's shelves unless they pass a replicated trial first. That is what Western Canadian agriculture built through hard times: farmers who do the work whether the times demand it or not.

Dennis Bulani is CEO of Rack Petroleum and Ultimate Yield in Biggar, Saskatchewan. Dan Aberhart hosts GTF Productions, Western Canadian Agriculture's foremost live briefing platform and its foremost AI training platform for ag operators