Bertha armyworm is a native pest so it has lots of natural enemies. If berthas are below thresholds, it may be best to avoid spraying and let these beneficials do their work.
A few important beneficials:
–tachinid fly
–parasitic wasp (Banchus flavescens)
–fungus
–virus
Among these beneficials, the virus is mostly likely to bring down an outbreak cycle. Infected berthas climb to the top of plants, go all gooey, and rain down virus on the worms below. It can spread fast.
If a canola field has a lot of berthas on the pods, make sure they’re actually eating. A lot of them may be dead.
Bertha loves quinoa (and a few weeds)
Why are some fields overrun with berthas while nearby fields have so few? Timing of canola flowering and the attraction of alternate host plants (weeds in the crop) are possible factors. For example, fields with a lot of kochia, lamb's-quarters, wild mustard or quinoa could be more attractive to egg-laying bertha armyworm moths. (Quinoa is not that common but berthas love it!)
However, once bertha armyworm have eaten one field, they will march – like a big army – across the road and into the next host field.
Which leads us to a reminder about risk maps: If you’re not in a high risk area, based on the provincial maps, you still want to look. Maps may have missed the timing of peak emergence in some areas. Hyper-local outbreaks do happen. In southern Alberta this week, growers experienced huge numbers in one area and very low numbers within a small radius. Risk maps for Saskatchewan Alberta Manitoba
Click here to see more...