The arrival of warm, sunny weather after planting brings with it the possibility for flea beetle damage to young canola plants, and therefore the need to be regularly scouting canola fields.
Flea beetles are an insect pest in canola that have the potential to cause lasting damage to the crop stand through their feeding activity. Canola is susceptible to damage from flea beetles from emergence until it reaches the four-leaf stage; prior to this stage the feeding activity of the beetles may cause enough leaf defoliation and/or damage to the growing points of the plant to significantly reduce plant stand and yield.
Flea beetle damage can become a concern when a number of risk factors occur together, such as the population level of flea beetles and timing with emergence, weather conditions, and canola stand establishment. Economically damaging infestations have the potential to occur in fields with poor stand establishment and under warm, dry conditions, which encourages flea beetle feeding. Canola Council of Canada states that canola is able to outgrow up to 50% cotyledon damage without impact to yield, if conditions favor rapid canola growth (like plant available moisture) or lower flea beetle pressure (through rainy days). However, they recommend scouting every few days–and every day if possible–when indications are favoring flea beetle predation. Scouting should evaluate the level of damage on canola cotyledons and leaves, and to consider the current and forecasted weather conditions. The economic action threshold for a possible foliar insecticide under these conditions is 25% leaf damage and defoliation, if flea beetles are still present and actively feeding. Flea beetle damage is often greater on the edges of fields–they may not have spread all throughout the field–which should be noted for both scouting and action plan decisions.
Useful links:
https://www.canolacouncil.org/canola-encyclopedia/insects/flea-beetles/
https://www.canolacouncil.org/canola-watch/fundamentals/the-flea-beetle-spray-decision-8-steps/
For questions or comments, contact Rachel via email at rachel.wieme@wsu.edu.