By James Tansey PhD, Saskatchewan Provincial Insect/Pest Specialist, Regina
The cereal leaf beetle (CLB), Oulema melanopus (L), is an invasive pest, originally from temperate Europe and Asia, that found its way to Saskatchewan in 2008. Although it is not currently considered a serious pest on the Prairies, it can cause localized economic damage. Damage is caused by the feeding of both adults and larvae, and characterized by the removal of longitudinal strips between leaf veins.
Adults are about 6 mm in length and have an orange thorax (the region just behind the head) and legs, and blue-black, metallic elytra ("the shell" – these are, in fact, the first pair of wings, hardened for protection). Larvae look like a little wet bag or oil droplet with a head and short legs. Larvae have the peculiar habit of covering themselves with their own feces. It is thought that this gives a measure of protection from predators. Eggs are about 1 mm long and yellow, and are deposited in pairs or individually on the upper leaf surfaces.
The beetle overwinters in shelterbelts and under plant debris as an adult. Females need to feed for a time on grasses near their overwintering sites before they lay eggs. Egg-laying begins in early May and can continue through mid-June. Winter wheat and early cereal crops are the first to be attacked in the spring. The beetle prefers wheat, oats and barley to rye and timothy. They will occasionally attack corn.
Larvae feed on the upper surface of leaves from June through late July. Damage increases as the larvae grow. Once larvae are mature, they fall to the ground to pupate in an earthen cell, generally no deeper than two inches. Pupation typically begins in mid-July. Next-generation adults begin to emerge early-August and can be present until mid-September.
Although there are insecticides registered to control CLB, biological control can be very effective and is the preferred long-term option. The parasitic wasp Tetrasticus julis (Eulophidae) attacks CLB larvae and can greatly reduce their populations. Parasitic wasps track CLB populations and may already be in areas with established populations of the host.
If CLB is spotted, please contact Dr. James Tansey with the Saskatchewan Ministry of Agriculture at 306-787-4669 or Dr. Haley Catton of AAFC, Lethbridge at 403-317-3404. The parasitoid may be available for release on request.