Cephus pygmaeus L. - European Wheat Stem Sawfly.

Systematic position.

Class Insecta, order Hymenoptera, family Cephidae, genus Cephus.

Biological group.

Pest of grain cereal crops.

Morphology and biology.

Body length 5-11 mm; primary color is black; 3rd to 6th abdominal segments have yellow transversal bordering their widest sections up to the 9th segment. Hind tibiae black from inner side, legs otherwise dirty yellow. Thorax with yellow spots from below. Sheath of ovipositor not enlarging apicad. Larval length reaches 10-15 mm; larva yellowish white with hazel head. S-shaped body without legs, curved, covered with sparse, short hairs. Anal segment is prolate, forming short, chitinized tube. Female lays 35-50 eggs, depositing them one by one in cereal stems, more frequently in upper internodes. Development of egg lasts 6 to 8 days; larval development lasts 20 to 40 days, depending on weather/climatic conditions in the area. Larva develops inside stem infested by egg. Developing larvae crawl down into lower part of stem, gnawing through internodes of culm. Larvae usually complete their development before the grain begins to ripen. During this period, damaged stem is easily distinguished by blacked-out area on culm below internode. The fully developed larva overwinters as pronymph. Pupation occurs in spring (from April until the first half of June); pupal stage lasts 7 to 10 days.


European part of the former USSR to Latvia, southern Leningrad and Yaroslavl Regions; Crimea, the Caucasus, Transcaucasia, Western Siberia, Middle Asia; most common in forest-steppe and steppe zones. Widespread in Western Europe, Northern Africa, the Middle East (north Iran, Iraq, Syria), Hindustan, and southeastern Asia. Introduced into Canada and the USA.


Flight of adults starts between April and June, depending on latitude, with degree days (above 10°C) of 208-243°C; in Ukraine and Northern Caucasus, flight usually coincides with the beginning of flowering of white acacia, and the maximum insect numbers occur during ear formation by winter wheat and during the tillering of spring wheat. Additional feeding occurs for 5-6 days on flowers of crucifers and composites. Adults prefer well-developed stems with thick and hollow culms for oviposition. Females saw through the wall of culm with ovipositor for egg-laying. Larva lives inside the stem, feeding on tissues around fiberous vascular bundles. Core parenchyma also does not possess necessary food quality. Moreover, if the parenchyma fills the central hollow of stem (so-called "filled" wheats), larvae perish for the most part, and surviving individuals grow to a lesser size and exhibit low fecundity. After completion of feeding, the larva saws stem from inside at the height of a few centimeters above tillering node, plugs the stem up with a cork made of sawdust, and weaves a thin, semi-translucent, waterproof cocoon, where it overwinters. Monovoltine, partly biennial species. Some larvae (up to 20%) do not pupate in spring, remaining instead in a state of diapause; this is considered an adaptation that enables them to survive adverse environmental conditions. Cold and snowy winters result in a higher death rate of overwintering larvae (50% or more). Death of 30 to 80% of insects occurs when springs are hot and dry, due to unfavorable conditions for their metamorphosis. A summer drought causing the withering of plants provokes death of up to 50% or more of larvae of early instars. Entomophagous insects, primarily the specialized parasite Collyria coxator, regulate the sawfly numbers, destroying as many as 80% of the sawfly larvae.

Economic importance.

One of the most economically important insect pests of winter and spring soft wheat; also causes damage to hard wheat, rye, and winter and spring barley. To a lesser degree, it damages oats and millet. It also damages various sown and wild grasses, including brome, couch-grass (false wheat), timothy, and wild oat. Weight of grain decreases, and grain quality decreases because of damage to conducting vascular fibers by larvae. The under-sawed stems easily break off; as a result, losses of grain increase at harvest. Harmfulness of the Wheat Stem Sawfly varies widely, from 3 to 30%, depending on stem infestation. Control measures include stubbling and deep autumn plowing-in of stubble; harvesting as early as possible; two-phase harvesting of wheat with a close cut; use of resistant varieties with "filled" stems; and growing of less susceptible crops (oats, millet). Treatment by chemicals during the period of adult flight is ineffective; burning out of stubble does not substantially influence the larval death rate, but it does promote higher levels of entomophages mortality.

Related references.

Belyaev, I.M. 1974. Pests of grain crops. Moscow: Kolos. 284 p. (in Russian).
Gussakovskii, V.V. 1935. Fauna of the USSR. Hymenoptera. V. 2. Issue 1. Horntails and sawflies, part 1. Moscow & Leningrad: Zoologicheskii Institut AN SSSR. P. 118-120 (In Russian).
Kazdokhova, L.Kh. 1975. Distribution and harmfulness of wheat stem sawfly in Kabardino-Balkar Autonomous Republic during 1961-1972. In: Voprosy selektsii ozimoi pshenitsy na ustoichivost' k khlebnym pilil'shchikam. Trudy Stavropol' Instituta sel'skogo khozyaistva, 21, Stavropol'. P. 83-86. (In Russian).
Konstantinova A.D., 1975. Wheat stem sawflies and their agricultural control in Volga region. In: Voprosy selektsii ozimoi pshenitsy na ustoichivost' k khlebnym pilil'shchikam. Trudy Stavropol' Instituta sel'skogo khozyaistva, 21, Stavropol'. P. 87-92. (In Russian).
Muche H. Die Cephidae der Erde // Dtsch. Entomol. Zschrft. 1981. Neue Folfe Band 28, Heft 4-5. S.239-295. (In German).
Shchegolev, V. 1931. Wheat stem sawflies (biology, ecology, control). Out of works of entomological department of the North Caucasus Regional Agricultural Experiment Station. 2nd Edition. Moscow & Leningrad: Sel'kolkhozgiz. 112 p. (In Russian).
Tanskii, V.N. & Dormidontova, G.N. 1987. Biological peculiarities of harmfulness of wheat stem sawfly Cephus pygmaeus L. (Hymenoptera, Cephidae). Entomologicheskoe obozrenie, 66 (4). P. 715-726. (In Russian).
Vinogradova, N.M. 1975. Distribution and harmfulness of wheat stem sawflies in the USSR. In: Voprosy selektsii ozimoi pshenitsy na ustoichivost' k khlebnym pilil'shchikam. Trudy Stavropol' Instituta sel'skogo khozyaistva, 21, Stavropol'. P. 54-59. (In Russian).
Zavertyaeva, L.M. 1976. Techniques to estimate wheat resistance to stem sawflies. In: Proceedings VIZR "Voprosy ekologii vrednykh nasekomykh". Leningrad. P. 139-144 (In Russian).
Zhasanov, F.K. 1991. European wheat stem sawfly, Cephus pygmaeus L. (Hymenoptera, Cephidae) in West Kazakhstan and scientific backgrounds for its control. Abstract of Candidate Thesis. Agric. Sci., Alma-Ata: Kazakh Institut sel'skogo khozyaistva, 25 p. (In Russian)

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