Cereal Leaf Beetle

species: oulema melanopus
common names: cereal leaf beetle
hosts: wheat, oats, barley (least preferred)
notes:

Agriculture and Agri-Food Canada Insect Identification Sheet No. 14 1975 Cereal Leaf Beetle Oulema melanopus (Linnaeus) The cereal leaf beetle is relatively new to North America. The first infestation in Canada was found in southwestern Ontario in 1967. Restrictions govern the movement of host materials out of quarantined areas of Ontario.

Injury:

Cereal crops, such as wheat, oats, barley and corn, and some grasses, are severely damaged by this insect. Both adult beetles and larvae damage plants by chewing out long strips of tissue between veins of the leaves. When damage is extensive, the leaves turn whitish and the plants appear as if injured by frost. The plants may be killed, or the crop may be seriously reduced.

Life Cycle:

The adult beetle is about 3/16 in. (5 mm) long and has bluish-black wing covers and head. The legs and thorax are reddish orange. The adults overwinter in trash, under loose tree bark, in old corn stalks and other places affording suitable shelter. Warm spring weather brings the beetles out and they begin feeding on wild grasses. Later they fly to nearby fields of winter wheat and subsequently move to fields of emerging oats where they feed for about 2 weeks before laying their eggs. Later emerging beetles will attack corn when it appears, although they prefer cereals.

The eggs, about pin-head size, are yellowish when newly laid but become almost black as they mature. They are laid singly or in rows of three or four. On corn, they are laid on the underside of the leaves, on other cereals they will be found on the upper surfaces.

Eggs normally hatch in 5 days and the slug-like larvae feed on the leaves for about 10 days. Then they move into the soil to pupate, emerging as beetles in 2 to 3 weeks. After feeding for about 2 weeks on corn or other late cereal crops, these beetles go into summer hibernation. Later they seek sheltered spots to pass the winter.

Pest Management:

Consult your provincial agricultural representative for recommendations on chemical control of the cereal leaf beetle.

Subject: Cereal Leaf Beetle

Cereal Leaf Beetle Fact Sheet No. 84, February 1993 Dr. Jay B Karren, Extension Entomologi

Introduction:

The cereal leaf beetle, Oulema melanopus (Linn.) has continued to slowly spread to new counties in Utah since its first discovery in Morgan County in June of 1984. Although it has not produced economic damage in all countries evidence of its presence has been found in Box Elder, Cache, Rich, Weber, Morgan, Summit, Davis, Salt Lake, Utah, Juab, Sanpete, Wasatch and Uintah Counties. All other counties in the state have been surveyed without any positive identification of either damage or the leaf
beetles. However, it will no doubt continue to spread.

The cereal leaf beetle is not difficult to control, and a serious outbreak can be stopped if discovered early and proper control measures are taken. Wheat and oats are the most susceptible to leaf beetle damage which may reach 30-50%. Barley is the least preferred small grain host and will probably be spared from attack in most areas.

Life History and Biology:

The adult beetle overwinters in weeds and grasses found in wooded areas or along fence rows. They often crawl into crack and crevices, under bark, or the hollow stems of plants for protection. Early in the spring, when temperatures reach about 50xF, the adults come out of hibernation and begin to feed. Adults have been observed in Utah in early April, but normally full activity doesn't occur until May. The adults are able fliers and fly to suitable grasses and winter or spring grains when available. These adults are heavy feeders, causing a characteristic feeding damage by eating completely through the leaves, leaving elongate, rectangular holes.

Usually within ten days after emergence and feeding, the mature eggs usually singly or in rows the upper surface of the leaf. They are laid on their sides and stuck firmly to the leaves with a gelatinous material.

The eggs are cylindrical, round, 1 mm in length, and light yellow in color with a clear spot at one end. Just before hatching, the clear spot enlarges, the yellow color turns dark, and the head and appendages become visible within the egg. Eggs hatch in 4-23 days depending on the temperatures. In Utah, we expect the first eggs to hatch about the first week in May. Peak egg hatch should be during the last week of May, and peals larval populations will appear about mid-June.

Shortly after the larvae emerge from the egg, they begin to feed on the upper surface of the leaves, removing the chlorophyll of the leaf down to the cuticle and between veins. This produces the characteristic skeletonized feeding damage on the leaf. Over an entire field, the crop takes on a "frosted" appearance. The larvae cover themselves with a mixture of mucous and feces so that they resemble a small slug feeding on the leaves. This covering is believed to protect the larvae against desiccation and some natural enemies. It is easily removed and cast off by the larvae when disturbed. Farmers and other workers in an infested field soon have shoes, pants, shirts, and nets covered with the wet, slimy material.

Larvae feed and develop for 12-20 days. Once mature, the larvae drop to the ground, burrow into the soil, and pupate.

In two to three weeks, the second generation adults emerge, generally move out of the grain fields into corn or other more palatable crops or weeds, and feed for a short time. Feeding is characterized by eating entirely through the leaf surface, causing stripping as opposed to the skeletonizing caused by the larvae. The brightly colored summer adults feed for about two weeks then go into a resting state, seek some type of shelter, and become quiescent until the following spring. These adults are very active flyers and can disperse over a wide area before they go into summer estivation. There is only one generation per year that takes four to six weeks from adult to adult. There is some evidence that the fields, and many are still present when the grain is harvested.

Studies indicate beetles survive temperatures from 110 to -12xF. Beetles become active in the spring when temperatures reach 50- 55xF. They seek out fall or spring-planted wheat, oats and barley and begin laying eggs. Generally, they are not a problem on fall- planted small grains unless spring-planted grains are not available.

Low populations of beetles can often be found by checking obstructions downwind that low-flying insects will encounter. Fence rows, windbreaks, hillsides, or even buildings may act as an obstruction to stop the beetle's flight.

Host's Plants:

The cereal leaf beetle feeds on a wide range of host plants, both in the larvae and adult stages. It commonly feeds on barley, oats, wheat, spiltz, wild oats, grass, timothy canary grass, reed canary grass, annual ryegrass, perennial ryegrass, foxtail, and fescues. Adults may feed on corn, sorghum, and sudangrass. Plants that are least preferred by the beetles but can still serve as a host plant include bluegrass, millets, fescues, red broms, red top, and downy broms. The beetles prefer younger plants and younger growth on plants. They are rarely found on broad-leafed plants.

Parasite Introduction:

A very successful parasite introduction program has been carried out in the East. One egg and three larval parasites have become established and, in most cases, no chemical control is required
in those areas. Attempts have been made to bring the parasites to Utah. One larval parasite from an insectary in Morgan County seems to be at least partially successful in Utah. A second insectary has been established in the Farmington area with two releases of parasites in 1992. It is hoped that a parasite population sufficient for wide distribution will develop at this site. Plans are underway for two addition insectaries under the direction of the USDA-APHIS to be established during the summer of 1993.

Resistance Scientists have found that some resistance in wheat is due to pubescence or hairiness of the leaves. They have found that leaf hair length is more important than density in deterring egg laying. One problem with this type of plant resistance is that environmental differences can cause pubescence to vary from one leaf to another, from one plant to another, and from one year to the next. Resistant varieties will have to be tested under Utah conditions.

Chemical Control:

Chemical control is made available on the hardcopy fact sheet. Please contact the Extension Entomology / Plant Pathology office at 801-750-2515 for a copy.

Insect Identification Sheet No. 14 1975

Cereal Leaf Beetle:

Oulema melanopus (Linnaeus)

The cereal leaf beetle is relatively new to North America. The first infestation in Canada was found in southwestern Ontario in 1967. Restrictions govern the movement of host materials out of quarantined areas of Ontario.

Injury:

Cereal crops, such as wheat, oats, barley and corn, and some grasses, are severely damaged by this insect. Both adult beetles and larvae damage plants by chewing out long strips of tissue between veins of the leaves . When damage is extensive, the leaves turn whitish and the plants appear as if injured by frost. The plants may be killed, or the crop may be seriously reduced.

Life Cycle:

The adult beetle is about 3/16 in. (5 mm) long and has bluish-black wing covers and head. The legs and thorax are reddish orange. The adults overwinter in trash, under loose tree bark, in old corn stalks and other places affording suitable shelter. Warm spring weather brings the beetles out and they begin feeding on wild grasses. Later they fly to nearby fields of winter wheat and subsequently move to fields of emerging oats where they feed for about 2 weeks before laying their eggs. Later emerging beetles will attack corn when it appears, although they prefer cereals.

The eggs, about pin-head size, are yellowish when newly laid but become almost black as they mature. They are laid singly or in rows of three or four. On corn, they are laid on the underside of the leaves, on other cereals they will be found on the upper surfaces.

Eggs normally hatch in 5 days and the slug-like larvae feed on the leaves for about 10 days. Then they move into the soil to pupate, emerging as beetles in 2 to 3 weeks. After feeding for about 2 weeks on corn or other late cereal crops, these beetles go into summer hibernation. Later they seek sheltered spots to pass the winter.

Pest Management:

Consult your provincial agricultural representative for recommendations on chemical control of the cereal leaf beetle.