Forage Pest Update Spring 2020

True Armyworm:  Moth catching is underway on Vancouver Island and the Fraser Valley for this species, Mythimna unipuncta.  So far,  there have been sustained catches of moths on Vancouver Island, but no sign of Armyworm larvae in grass hay or corn.  In the Fraser Valley,  we are catching only about 1 moth per week so very low numbers and not of concern.  

Colleagues in WA and CA are also trapping for True Armyworm and will provide moths for the wing analysis by Dr. Jeremey McNeil at Western University later in the season.  We believe the BC moths are coming from California in the spring and this wing analysis is a way to test that, and it takes a few years to gather enough information to come to conclusions. 

 Western Yellowstriped Armyworm (Spodoptera praeficais being trapped for again in the North Okanagan.  While moths are being caught there hasn’t been any confirmed larvae/armyworm outbreaks on crops so far this year.  

Other caterpillars in hay:  There are reports of other  caterpillars in grass and corn at this time.  It is particularly noticeable on the haying equipment:  if you find lots of caterpillars, the best way to get identifications is by collecting them into a baggie or container with some grass and try to feed and keep them alive until they pupate and turn in adult moths—or get these collections to me in Abbotsford and we can rear them to adult moths.  Sometimes I or my colleagues can identify them from photos of the larvae but there are many similar looking species and  coloring can be naturally variable so we cannot always reach successful identifications using photos of larvae alone.

I am seeing photos of Alfalfa loopers (Autographa californica) which is a common early season caterpillar on corn, but it has only one generation per year and the corn can usually outgrow the damage.  It can look pretty concerning now but the caterpillars pupate soon and then disappear.  

Thank you for your notes and photos and sharing what is going on out there and I will continue to do my best to ID in a timely manner.  

Western corn rootworm:  Larvae of this pest will be active now in corn roots.  We will set up yellow sticky traps in corn to trap adult beetles in mid July.


Tracy Hueppelsheuser
Entomologist, Plant and Animal Health Branch
British Columbia Ministry of Agriculture
1767 Angus Campbell Road,
Abbotsford, British Columbia, V3G 2M3

Note New Phone Number:  778-666-0519