By: Scott Hartley, PAg, Provincial Specialist, Insect/Vertebrate Pest Management
The cereal leaf beetle (Order Coleoptera: Chrysomelidae - Oulema melanopus) is a recent invasive insect in Saskatchewan, first found in the southwest region of the province in 2008. Likely originating in temperate regions of Europe and Asia, it was first recorded in Michigan in the United States in 1962. It has since spread east and west. In western Canada, it first became established in the Creston Valley in British Columbia in 1998, and was found in southern Alberta in 2005 and Manitoba in 2009.
Cereal leaf beetle adults have orange to red legs and thorax, and bluish metallic wing coverings. The thorax is narrower than the front of the wing coverings on the abdomen. There are other similar-looking beetles, but they do not have all of these features. The larvae are unique in that they carry their fecal matter on their back leaving only the head, thorax and legs easily visible.
Cereal leaf beetles have one generation annually, over-wintering as adults in habitats similar to those of flea beetles (e.g. vegetative debris and shelterbelts). They emerge in the spring and feed on grass species near their over-wintering sites. Winter wheat or other early-emerged cereal crops are usually the first crops to be attacked in the spring.
Female adult beetles may lay eggs immediately or feed for a period of time before laying most of their eggs in May. The eggs hatch in five to ten days under favourable environmental conditions. The larvae may feed from June to July, with the later larval instars causing the most damage (Photo 2). Once fully mature, the larvae drop to the ground to pupate in the top two inches of soil. The new adults will emerge from the pupae and begin feeding before moving to over-wintering sites outside the field.
Damage from the cereal leaf beetle to cereal crops is characterized by longitudinal feeding between the leaf veins . Both adults and larvae consume cereal plant tissue in a lengthwise pattern between the parallel leaf veins. Larvae chew the upper surface of leaves, while the adults tend to chew completely through the leaf.
There are insecticides registered for control of the cereal leaf beetle. However, this is an insect where biological control through a wasp parasite has been very effective at keeping cereal leaf beetle populations below economic threshold (Photo 4). If any of the life stages of the beetle are identified in an area, Agriculture and Agri-Food Canada (AAFC), Lethbridge, has a rearing facility for the parasites and will ship them for release in the area. Contact your local Regional Agronomist if you suspect you have cereal leaf beetle.
Although bio-climatic models produced by AAFC indicate that much of the cereal-growing regions of the Prairies are suitable for survival of the beetle, as of 2015 surveys have only found the cereal leaf beetle in the southwest (south of Maple Creek) and on the east side of Saskatchewan near Moosomin.