Friday, 2 June 2017

Weekly Update (Jun 1, 2017; Wk 05) - Predicted Bertha Armyworm Development

Bertha armyworm (Lepidoptera: Mamestra configurata- As of May 28th, predicted pupal development is well underway. We are fortunate to have two methods projecting pupal development:
--> Figure 1 reflects pupal development BASED ON DEGREE DAYS ONLY.
--> Figure 2 reflects pupal development BASED ON CLIMEX MODELLING (i.e., incorporates environmental data + biological data for organisms) AND legend is designed to estimate WHEN PHEROMONE TRAPS SHOULD BE DEPLOYED (i.e., pheromone traps are best deployed at ~80% pupal development). 

Figure 1. Predicted stage of pupal development of overwintered Bertha armyworm (based on Degree-Day heat units) set to emerge in 2017.

FIGURE 2. Predicted pupal development of Bertha armyworm (based on Climex model and legend designed to reflect that pheromone traps are best deployed at ~80% pupal development).

More specifically, Figure 2 shows the average pupal development is 50% (36% last week), and as high as 75% at a number of locations. The three graphs below show that adult emergence is predicted to be six days sooner in the Winnipeg region than in fields near Vegreville and ten days sooner than the Yorkton area.  

IMPORTANT - The table indicates predicted dates of first appearance of adults for specific locations across the prairies. We generally suggest that traps go out when pupal development is at 80%. Adult emergence generally occurs within 5-7 days after 80% development. As of May 29, 2017, there is a large area in southern Alberta that is greater than 70%. 

Reminder - These maps will be updated weekly to aid those who deploy and monitor this moth using pheromone traps.  The video below posted by Alberta Agriculture and Forestry's Scott Meers describes how pheromone traps are used to monitor this important pest of canola.

Biological and monitoring information related to bertha armyworm in field crops is posted by the provinces of ManitobaSaskatchewanAlberta and the Prairie Pest Monitoring Network.  Also refer to the bertha armyworm pages within the new "Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide" - both English-enhanced or French-enhanced versions are available.