Cereal leaf beetle (Oulema melanopus) - The CLB simulation model will be used to monitor this insect pest's development across the prairies. Weekly temperature data collected across the prairies is incorporated into the simulation model which calculates estimates of development stages based on biological parameters for this species.
The cereal leaf beetle (CLB) model indicates that oviposition is well underway (Fig. 1 and 2). First instar larvae should be appearing within the next 7-10 days.
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| Figure 1. Predicted cereal leaf beetle phenology at Lethbridge AB. Values are based on model simulations (April 1-May 18, 2020). |
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| Figure 2. Predicted cereal leaf beetle phenology at Winnipeg MB. Values are based on model simulations (April 1-May 18, 2020). |
Lifecycle and Damage:
Adult: Adult cereal leaf beetles (CLB) have shiny bluish-black wing-covers (Fig. 4). The thorax and legs are light orange-brown. Females (4.9 to 5.5 mm) are slightly larger than the males (4.4 to 5 mm). Adult beetles overwinter in and along the margins of grain fields in protected places such as in straw stubble, under crop and leaf litter, and in the crevices of tree bark. They favour sites adjacent to shelter belts, deciduous and conifer forests. They emerge in the spring once temperature reaches 10-15 ºC and are active for about 6 weeks. They usually begin feeding on grasses, then move into winter cereals and later into spring cereals.  |
| Figure 4. Adult Oulema melanopus measure 4.4-5.5 mm long (Photo: M. Dolinski). |
Egg: Eggs are laid approximately 14 days following the emergence of the adults. Eggs are laid singly or in pairs along the mid vein on the upper side of the leaf and are cylindrical, measuring 0.9 mm by 0.4 mm, and yellowish in colour. Eggs darken to black just before hatching.
Larva: The larvae hatch in about 5 days and feed for about 3 weeks, passing through 4 growth stages (instars). The head and legs are brownish-black; the body is yellowish. Larvae are usually covered with a secretion of mucus and fecal material, giving them a shiny black, wet appearance (Fig. 5). When the larva completes its growth, it drops to the ground and pupates in the soil.
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| Figure 5. Larval stage of Oulema melanopus with characteristic feeding damage visible on leaf (Photo: M. Dolinski). |
NEW for Manitobans - Dr. John Gavloski is looking for samples of cereal leaf beetle larvae this growing season to determine their range across Manitoba, their population density, and the rate at which larvae are parasitized. Please contact John (John.Gavloski@gov.mb.ca) or @JohnTheBugGuy if you observe cereal leaf beetles in your fields.
