A small, bright-red insect that can devour crops and is native to North America has been lurking in Saskatchewan soils for a long time.
However, little is known about it.
“It’s a curiosity for most of the ag community, unless you’re actually experiencing an outbreak and then it’s a nightmare,” said James Tansey, provincial insect and vertebrate pest specialist with Saskatchewan Agriculture.
He spoke about the pest during a Knowledge Centre presentation held as part of Ag in Motion Discovery Plus July 21-26.
Peritrechus convivus is a species of dirt-coloured seed bug in the family rhyparochromidae. With about 2,100 species worldwide, the bright-red bug tends to be found in lighter soils from Canada to Mexico.
Not to be confused with bright-red insects like the white-margined burrower or harlequin bug, peritrechus convivus are more streamlined and not as round.
Peritrechus convivus congregate in very large numbers during the nymph stage and look like the adults as they grow wing buds and get progressively bigger.
“They really like each other’s company and it can aggregate in huge numbers,” said Tansey.
Reports are sporadic and not much is known about geographic distribution, but it has been found in central Saskatchewan.
Its habitat appears to be correlated to wet areas characterized by cattail growth, which tends to get cultivated during drier periods.
“We’re in a relatively dry period and those low lying, traditionally wet areas are now getting seeded and those are some of the areas that seem to be hit. But there are always exceptions to rules and I actually did find some on a hilltop this past spring,” he said.
He also discovered a large population of ground beetles thriving in the same area, which might suggest a natural enemy.
“Whether they were directly feeding on them — I find it hard to believe that a predator would simply coincidentally be in close association with prey. It seems that there should be a number of generalists that will feed upon these,” he said.
While it’s not a perennial pest and outbreaks don’t appear to be common, Tansey said there’s no information about why millions can suddenly appear and wreak havoc on crops like canola, corn, and cereals.
“It seems the host range of the animal is very broad. What exactly is encompassing the host range … is still being worked out,” he said.
“Damage tends to be localized, but where it does occur, can be very heavy. We had a report from last year of a half section of canola being lost and multiple reports of 20- to 50-acre parts of corn fields being lost to it,” he said.
Like lygus bugs or aphids, which are piercing sucking feeders, Peritrechus convivus sticks its proboscis into the plant and draws out vascular fluids, which causes plants to lose turgor and wilt.
He said farmers should scout for aggregations of the bright-red insects living relatively low on the plant, although they can amass in large numbers on the leaves.
“I have seen photos of canola plants just covered in these creatures. Great areas of crops can be cleared. Part of the reason for this is the very dense aggregations and the numbers can just be absolutely astounding, I mean, by the millions,” he said.
There are currently no economic thresholds for when to apply spray control because no chemical products are registered.
“We have a difficult time making control recommendations based on those two parameters,” he said.
Growers who have applied insecticide report mixed results.
“Part of the rub is that this animal spends a lot of time underground. So a lot of the contact insecticides are never even going to touch it. You need something with good residue time or with systemic activity for it to have an effect,” he said.
There are no upcoming dedicated proposals to study the insect pest, but Agriculture Canada is trying to include it with other research projects.
Tansey said producers can reach out to him or Tyler West at Agriculture Canada for more information.