By James Tansey, PhD AAg, Provincial Insect/Pest Management Specialist, Regina
In early to mid-June of 2017, several reports of heavy infestations of "red bugs" in young canola crops were received in Alberta and Saskatchewan. Early speculation was that the insects were nymphs (juveniles) of the twice-stabbed stink bug, Cosmopepla bimaculata, or the white-margined burrower bug, Sehirus cinctus. These two species were observed congregating on canola seedlings in past years. Nymphs of both species are red and can be damaging, though rarely at economic levels.
However, in 2017, some large populations appeared to be another species. Samples of nymphs were collected, and adults were reared for identification by Agriculture and Agri-Food Canada (AAFC) and the National Identification Service in Ottawa. This work indicated Peritrechus convivus (no common name) as the true identity of these peculiar little red bugs.
This insect is a member of the Rhyparochromidae, the family of insects called the “dirt-coloured seed bugs.” This is a relatively diverse group with about 2,100 species worldwide. P. convivus is believed to be a native to North America, and historically was called P. saskatchewanensis. This name was proposed after the initial description as P. convivus and is now considered a junior synonym, but is not commonly used.
The nymphs are the damaging stage and can occur at high densities. Feeding with piercing-sucking mouthparts occurs on developing stems of seedlings. Adults can also occur at very large numbers but are thought to feed on seeds under the soil surface. The host plants (species that the insect feeds on) seems very broad. In addition to canola, several reports of large-scale, though localized, damage were reported in field corn and flax in 2018 and 2019, and reports of large numbers of nymphs in cereals occurred in 2019. In addition, there are anecdotal accounts of greater pressures of these insects in low-lying spots in fields that have historically been wetlands characterized by cattails.
There has been overwhelming damage caused by these insects to seedlings, to the extent that large areas of fields can be completely decimated and control was deemed necessary. Control attempts with pyrethroids and chlorpyrifos achieved limited success. The responses of these insects to insecticides is poorly understood and more research is required. No products are currently labeled for this insect in any crop, so recommendations for control are lacking.
Information on Peritrechus convivus continues to be gathered, and there is still much to learn. Please contact the Ministry of Agriculture or AAFC if you see large aggregations of peculiar little red bugs in crops.