Heavy fall armyworm pressure in Ont.

Heavy fall armyworm pressure in Ont.
Sep 03, 2021

The pest can move quickly, decimating the leaves on many types of crops

By Jackie Clark
Staff Writer

Producers are finding fall armyworm (FAW) in their crops, according to an August 30 report from Tracey Baute, entomologist for the Ontario Ministry of Agriculture, Food and Rural Affairs. 

“Growers or scouts drive by a field and pull over, shocked to see only stems left of plants with larvae happily feeding. So far most of the damage has been found in oats, rye cover crop, mixed forages and newly seeded cereals,” she explains in the report. “Unfortunately, from the calls so far in Ontario, the larvae have been too big -- larger than 1 inch -- for insecticides to be effective but thankfully these larger larvae won’t be feeding much longer before they start to pupate.”

Matt Rundle, an NK agronomist for Syngenta, was surprised to see the amount of FAW pressure this year. 

“The fall armyworm is typically not a pest we deal with in large numbers, but this season, a large population of moths arrived in Ontario, migrating up from the southern US,” he explains. “Those moths have mated, and now their larval offspring are wreaking havoc, particularly in our hay and forage cover crops in South/West Ontario. They are being found in patches, but as their name suggests, they can move through a crop and destroy in a short period of time.”

Different from the true armyworm, FAW will attack broad-leaved forages like alfalfa in addition to small grains and corn, he added. 

“In corn, late planted fields are at most risk. The moths are attracted to them as they know it will provide their offspring with a food source for the longest time possible, he said. “In small grains, cover crops and forages, the armyworm moths are attracted to thick, lush canopies. Areas of the field with planter overlap are a great place to start scouting.”

Control options depend on the size of FAW in the field, Rundle said. The Agrisure Viptera trait also controls FAW. 

“In forage cover crops, early cutting is an option,” he adds. 

“In hay, the conversations get really tricky because we are past the critical fall resting period for some areas of the province,” he explains. “We do not want to cut the hay crop too late and risk overwintering damage to the alfalfa crowns. This requires an in-depth discussion considering factors such as how long the field is intended to be in hay, the pressure of the fall armyworm, and the number of acres it is affecting.”

FAW are a migratory pest, and will not survive winter, he adds. Regular scouting is key to staying on top of this pest for the remainder of the season. 

miwa_in_oz\iStock\Getty Images Plus photo

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