A fall 2020 survey by AMVAC compared 2020 corn rootworm pressure to that of 2012, after which, use of soil-applied insecticides was elevated for the three seasons of 2013-2015.
Jim Lappin of AMVAC says retailers saw an increase in corn rootworm pressure in 2020, and expect the same trend in 2021.
“Our goal was to talk to our retailers about the coming season to make sure we would be able to serve the needs that they saw developing in the market coming forward. Overwhelmingly, we heard from retailers that they’re anticipating an uptick in soil insecticide demand based on a higher-than-normal corn rootworm activity, or rootworm activity more reminiscent of what we saw back in 2012-2013.”
Lappin says there are many reasons why there is more corn rootworm pressure in 2020 and heading into 2021. The ideal growing condition for corn is also ideal conditions for corn rootworm, and weed control can play a factor as well.
“Going into early June, there were a lot of growers told they may not have the ability to spray dicamba later in the season, so a lot of guys ran out and made earlier applications of dicamba and what that resulted in is that dicamba has a limited residual period. So, all of a sudden you had really clean fields in June after they sprayed, but then as the season progressed, as more rainfall occurred, now of a sudden you had some late season weeds that came through, and those created extra places for rootworm the feed.”
Lappin says the best way to combat corn rootworm is rotating crops.