Thursday, 5 July 2018

Predicted bertha armyworm development (Jul 05, 2018; Wk 09)

Bertha armyworm (Lepidoptera: Mamestra configurataBAW populations are predicted to be in the larval stages and may have begun feeding within the plant canopy on leaves. Figure 1 illustrates that BAW oviposition is complete and  that the population is in the larval stage for populations near Brandon (Fig. 1). 

Figure 1.  Predicted BAW phenoloyg at Brandon MB. 
Values are based on model simulations for April 1-July 2, 2018 (projected to July 10, 2018)

Many thanks to those who are checking a bertha armyworm pheromone trap on a weekly basis.  Please use the reference photo below kindly shared by Saskatchewan Agriculture to aid your identification and reporting of trap interceptions.  Note the kidney-bean white-patterned shape on each forewing but also know other cutworm species can resemble bertha armyworm moths.  Check carefully and thanks for your help!

- Larval sampling should commence once the adult moths are noted. 
- Sample at least three locations, a minimum of 50 m apart. 
- At each location, mark an area of 1 m2 and beat the plants growing within that area to dislodge the larvae. 
- Count them and compare the average against the values in the economic threshold table below:  

Scouting tips:
● Some bertha armyworm larvae remain green or pale brown throughout their larval life. 
● Large larvae may drop off the plants and curl up when disturbed, a defensive behavior typical of cutworms and armyworms. 
● Young larvae chew irregular holes in leaves, but normally cause little damage. The fifth and sixth instar stages cause the most damage by defoliation and seed pod consumption. Crop losses due to pod feeding will be most severe if there are few leaves. 
● Larvae eat the outer green layer of the stems and pods exposing the white tissue. 

● At maturity, in late summer or early fall, larvae burrow into the ground and form pupae.

Keep track of the Provincial Entomologist Updates for the latest in-season pheromone trap monitoring results for 2018.  

Saskatchewanians can view the latest pheromone trap interceptions below kindly provided by Saskatchewan Agriculture.

Albertans can access the online reporting map (screenshot retrieved 04Jul018 provided below for reference:

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.