Farmers have been reporting healthy aphid numbers this year, and based on the number of ground rigs and airplanes spotted throughout the state, folks have been aggressively treating these damaging little sacks of goo.
My extension theme for the year has been focused around thorough scouting and aggressive treatment of observed and harmful pests. The aphid is a perfect example of where farmers have been getting it right … mostly. In farming, as in any good 12 step program, accepting that we have a problem is the starting point. Farmers have accepted that aphids are a damaging lot, and that failure to treat them will wreak financial havoc on the bottom line. But for many, the next steps have strayed a bit from the program.
First, the availability of cheap insecticides has prompted many to prophylactically tank-mix them with herbicides and or fungicides as a cheap form of insurance against a mid-season colonization event. As with most easy ways out, this path has some significant short- and long-term downsides. These will be discussed in more detail in subsequent “Production Notes.”
Second, even when scouting and spraying has been carried out correctly (e.g. weekly scouting, more than 250 aphids per plant, and with 80 percent of plants having aphids – see the U of M guide for soybean aphid scouting), it is extremely easy to walk away from fields confidently wiping your hands of any insect problems. This is a mistake.
Entomologists, Robert Koch, Bruce Potter, Ian MacRae, and Ken Ostlie highlight this in a recent Minnesota Crop News article. With rapid aphid reproduction, significant aphid dispersal across the state and recent reports of insecticide failures, it’s critically important to re-scout fields on a weekly basis after treating a field. Even in the absence of an application/product failure, recolonization of fields often occurs sooner and more heavily than producers expect. Mid-late season aphid pressure can have a dramatic effect on soybean yields.
If fields require a re-treatment, it’s critically important that a new insecticide be utilized. These products must have a different insecticide mode of action (not just trade names or variants within the same chemical family). Altering the mode of action will help increase chances of getting good insect control and will reduce chances of promoting the development of insecticide resistance (see the U of M fact sheet on insecticide resistance). THIS is a BIG deal.
Stay tuned for development on the fight against aphids in Minnesota. Likewise, expect to read more about resistance management in upcoming “Production Notes.”
Seth L. Naeve is a University of Minnesota Extension Soybean Agronomist and Associate Professor of Agronomy and Plant Genetics. Reach Seth at 612-625-4298 or email him at firstname.lastname@example.org.