Field Guide     Pest Management     Cereal Leaf Beetle

Cereal Leaf Beetle

CROPS IMPACTED: barley, brome grass, corn, oats, orchard grass, quackgrass, reed canary grass, rye, rye grass, timothy and wheat

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Family: Chrysomelidae

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About Cereal Leaf Beetle

Reproduction and Life Cycle

Throughout the winter, cereal leaf beetles overwinter and once the temperature is a steady 10 to 15˚C, the adult beetles emerge and will start mating and lying eggs about 14 days later. These eggs lay in pairs or alone along the mid-vein on the top side of leaves. Each female beetle has the ability to produce and lay several hundred eggs. After about 5 days the larva will hatch and feed for approximately 3 weeks, in which time they will go through 4 instar/molting stages. Once the larvae have gone through all molting stages they will fall to the ground and pupate under the soil surface. This stage of the cereal leaf beetles life will last about 2 to 3 weeks. At this time they will emerge as fully mature adults beetles, feed for a few weeks and then find an overwintering site. There is one generation of cereal leaf beetles per year and they are active for about 6 of those weeks.

Cereal Leaf Beetle Identification and Habitat

Identification

When trying to identify an adult cereal leaf beetle, look for their shiny bluish-black antenna, head, abdomen and wing-covers. Their legs and thorax are brown to light orange in colour. Male beetles are 4.4 to 5mm long and females are a little bigger, growing to about 4.9 to 5.5mm long. The eggs these females produce are very small at about 0.9mm by 0.4mm; they are yellowish in colour and round. Just before the eggs hatch they will change colour to black. The larva that emerges is slug-like and is longer than the adult beetles. Their body is yellowish with legs and a head that is black to brown in colour. Typically the larva is covered in this faecal and mucus material that gives their appearance a wet and shiny black look to it. After the larvae stage, cereal leaf beetles will pupate. They are enclosed in a thin, bright yellow cocoon, changing to their adult colour right before they emerge.

Habitat

Adult cereal leaf beetles overwinter in and around grain fields in protected areas such as tree bark, straw stubble and underneath leaf and crop litter. Once they emerge from overwintering, the beetles will feed on grasses, moving into winter and late spring cereal crops. These cereal crops would include barley, brome grass, corn, oats, orchard grass, quackgrass, reed canary grass, rye, rye grass, timothy, wheat and a few other grasses. Adults and larvae consume the same host plants listed above; they will eat these plants by chewing between the veins of leaf tissue. Adult cereal leaf beetles are able to eat all the way through the leaves, whereas the larvae will only eat the top surface, leaving behind a window-pane or “skeletonizing” effect on the leaves. When extensive damage has been done, the leaf turns a whitish colour and makes the plant look like it has been damaged by frost. If cereal leaf beetles are not managed, they are able to cause a serious reduction in yield. Note that most plant injury will occur by larva in June.

Cereal Leaf Beetle Control Methods

Chemical Control

There are a few recommended chemical control methods for cereal crops. There are many formulations of Malathion that are registered to control cereal leaf beetles. These chemicals are best applied when there are 2 to 3 cereal leaf beetles larvae per stem. Application can be repeated every 7 to 10 days, as needed. Make sure to apply these chemical when the temperature is higher than 18˚C and do not treat fields 7 days before harvesting. A second recommended chemical is Sevin XLR, also known as carbarly. It is important that you do not apply Sevin XLR 28 days before harvesting barley and 14 days before harvesting rye, wheat and oats. That being said, both these chemicals typically only need one application to reduce the infestation of cereal leaf beetles and lower the chances of crops reaching economic loss.

Latin / Alternative Cereal Leaf Beetle Names

  • - Oulema melanopus

Sources

http://www.omafra.gov.on.ca/english/crops/pub811/13cereal.htm#clbeetle

http://www.agf.gov.bc.ca/cropprot/clbeetle.htm