Thursday, 4 June 2020

Diamondback moth

Diamondback moth (Plutellidae: Plutella xylostella) - Once diamondback moth is present in the area, it is important to monitor individual canola fields for larvae.  Warm growing conditions can quickly translate into multiple generations in a very short period!

Wind Trajectory Updates - Wind trajectory models used to deliver an early-warning system for the origin and destination of migratory invasive species indicated arrival events of air currents potentially carrying migrating diamondback moths from more southerly regions.  Access the Weekly Wind Trajectory Report (released June 1, 2020) to review where wind trajectories originating over Mexico, California, Texas or the Pacific Northwest cross locations in Manitoba, Saskatchewan, and Alberta.

Weekly Pheromone-baited Trapping Results - Early season detection of diamondback moth is improved through the use of pheromone-baited delta traps deployed in fields across the Canadian prairies.  As they become available, moth reporting numbers observed in AlbertaSaskatchewan and Manitoba will be linked here.

Remove the plants in an area measuring 0.1 m² (about 12" square), beat them on to a clean surface and count the number of larvae (Fig. 1) dislodged from the plant. Repeat this procedure at least in five locations in the field to get an accurate count.

Figure 1. Diamondback larva measuring ~8 mm long.
Note brown head capsule and forked appearance of prolegs on posterior.

Figure 2. Diamondback moth pupa within silken cocoon.

Economic threshold for diamondback moth in canola at the advanced pod stage is 20 to 30 larvae/ 0.1  (approximately 2-3 larvae per plant).  Economic thresholds for canola or mustard in the early flowering stage are not available. However, insecticide applications are likely required at larval densities of 10 to 15 larvae/ 0.1  (approximately 1-2 larvae per plant).

Figure 3. Diamondback moth.

Biological and monitoring information for DBM is posted by Manitoba AgricultureSaskatchewan Agriculture, and the Prairie Pest Monitoring Network.  

More information about Diamondback moths can be found by accessing the pages from the  "Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and Field Guide".  View ONLY the Diamondback moth page but remember the guide is available as a free downloadable document as both an English-enhanced or French-enhanced version.