The cereal leaf beetle is a relatively new pest of cereals in Alberta, first spotted in 2005.
And, if you are Dr. Haley Catton, research scientist in cereal crop entomology with Agriculture and Agri-Food Canada, you’ll describe these creatures as a “beautiful, small, jewel-like beetle.” Those doing the scouting might not be so enamoured by the small, poop-covered insects.
In this episode of Real Agriculture’s Wheat School, Kara Oosterhuis joins Catton to talk all things cereal leaf beetles.
“The cereal leaf beetles overwinter as adults and lay their eggs in the spring on developing cereal plants. When those larvae hatch, they can cause a lot of defoliation damage to developing cereal crops,” Catton says, noting that defoliation damage most often occurs in early June.
When scouting in the field for the little larvae, you actually want to keep an eye on yourself for any leftover fecal matter, as that can often be a telltale sign they are in your fields.
Catton notes that although the adults will chew right through the leaf, making a window, the larvae will only eat the top part of the leaf, leaving white-looking stripes. (Story continues below)
Research in the U.S. has shown that around one larva per flag leaf is generally the rule of thumb for a control threshold; anything less than one larva per flag leaf is not worth spraying for.
“We’re looking to see if those numbers match up with what we see here in the Prairies. We’ve done some cage experiments, we’ve done some plot work, and we were never even able to achieve one larva per flag leaf. Despite dumping around 44 beetles per square metre in cages. So we have no reason to believe that economic threshold wouldn’t stand up here on the Prairies, based on our research.”
The most likely reasoning for the cereal leaf beetle staying under control in the Prairies is because of a beneficial insect — a little wasp called Tetrastichus julis (T. julis)
“The t. julus is one of the main reasons we don’t recommend spraying. When you spray out the cereal leaf beetles, you spray out their natural enemies too, which allows for the pest to bounce back.”