Cereal Leaf Beetle Behind Schedule
In a previous article I covered the reasons why it would not be a good idea to spray automatically for cereal leaf beetle this year (Reasons You Will Lose Money in 2014 Tank Mixing an Insecticide with Your Nitrogen Over Wheat). To add fuel to that argument, cereal leaf beetle is behind “normal” schedule this year.
The Southern Region IPM Center and NC and VA Small Grains Growers Associations funded a major research and sampling effort in 2010 and 2011. We found that we could accurately predict the peak egg lay of cereal leaf beetle within three days based on a temperature based model. The figure in this article details the time in which the peak egg lay occurred in these studies. This took place at 182 “degree days”. Degree days for cereal leaf beetle are calculated using temperature. The more degree days there are, the warmer it has been and the sooner cereal leaf beetle will emerge. In the study, peak egg lay in Plymouth, NC (182 degree days) occured around the end of March. However, as of 27 March 2014, Plymouth has only received 117 degree days. That means we are 65 degree days away from peak egg lay for cereal leaf beetle in Plymouth in 2014. I confirmed this by walking some wheat this afternoon. Plenty of Hessian fly eggs (two weeks later than last year when I observed eggs- article here), but not a single cereal leaf beetle egg.
It is important to note that insecticides are effective only on the larvae, not the eggs. Larvae tend to peak 2-3 weeks after egg lay. Furthermore, rain and other weather events can kill eggs. It is therefore more critical than ever to hold off insecticide for cereal leaf beetle this year since it is too early and may not be needed.