Plants > Plant Pests > Cereal Leaf Beetle  

Oulema melanopus L. - Cereal Leaf Beetle

BACKGROUND:

The cereal leaf beetle is a pest of cereals, grains and various grasses. This pest does have the potential to cause significant economic losses as was demonstrated in Hungary (1891), Romania (1931) and Spain (1938-39). In Russia reported losses have ranged from 25-50% of the cereal crop. The first North American infestation was reported from Berrien County, Michigan, USA in 1962. The first record for the cereal leaf beetle in Canada was reported in 1967 from southwestern Ontario.

HOSTS:

All cereals; barley (Hordeum spp.), wheat (Triticum spp.), oats (Avena spp.), rye (Secale spp.), corn (Zea mays) and wild grasses.

DISTRIBUTION:

• Asia: Afghanistan, Azerbaijan, China, Cyprus, Georgia, Iran, Israel, Kazakstan, Mongolia, Siberia, Syria, Turkey, Turkmenistan, Uzbekistan
• Europe: Throughout
• North Africa: Algeria, Morocco, Tunisia
• North America: Canada, USA

BIOLOGY:

Adults (Fig. 1) overwinter in clusters in protected places such as in the crevices of tree bark; under field trash; inside rolled leaves; they have even been found in bee hives. Sheltered places are vital for the survival of overwintering adults. Exposer to -15°C for about a week kills 90% of the overwintering population. The same result can be achieved with continuous exposer to 0°C for 110 days. Cereal Leaf Beetle adults become active in the spring, when the temperature reaches 20°C and feed initially on wild grasses. The adults later move onto winter wheat and young oat plants. Egg laying begins about 14 days after the emergence of the adults. The eggs are laid singly or in pairs (Fig. 2). They are fixed by an adhesive to the upper surface of blades of grass preferring a location half-way up the plant. Each female may lay 100 to 400 eggs over a 50 day period. The larvae (Fig. 3) hatch in about 5 days and begin feeding, passing through 4 instars. Each instar lasting 2-3 days. After feeding is completed, the full-grown larva enters the soil and pupates in earthen cells about 2.5 cm beneath the surface. The pupal stage lasts 2 to 3 weeks at which time the new adults emerge. The total time required to complete the life cycle is 46 days.

DETECTION & IDENTIFICATION:

Symptoms:

Both the adults and larvae severely damage plants by chewing out long strips of tissue between the veins of leaves (Figures 4 & 5), leaving only a thin membrane. When damage is extensive the leaves turn whitish and the plant takes on the appearance of frost damage (Fig. 6). The plant may be killed or the crop may be seriously reduced.

Identification:

• Adult: The colour pattern of these introduced beetles is the main distinction between them and their North American relatives. Both the male and female adult beetles have bluish-black wing-covers; head; antenna and abdomen. The thorax and legs are light orange-brown with the legs possessing some dark spots. Females (4.9 to 5.5 mm) are slightly larger than the males (4.4 to 5 mm).
• Egg: The egg is cylindrical, rounded and measures 0.9 mm by 0.4 mm. It is yellowish in colour darkening to black just before hatching.
• Larva: The slug-like larva is slightly longer than the adult. The head and legs are brown-black; the body is yellowish. The larva is usually covered by a globule of faecal matter that obscures its colouration.
• Pupa: The pupa, when removed from its earthen cell, is enveloped in a thin, transparent membrane. Its colour varies from a bright yellow when it is first formed, to the colour of the adult just before emergence.

Fig. 1 (183K)	Fig. 2 (85K)	Fig. 3 (131K)
Fig. 4 (166K)	Fig. 5 (174K)	Fig. 6 (153K)

Text: Plant Health Surveillance Unit.
Photos: Agriculture and Agri-Food Canada, Research Branch, Ottawa.