Loxostege sticticalis L. (= Pyrausta sticticalis L.) - Beet Webworm.

Systematic position.

Class Insecta, order Lepidoptera, family Pyralidae, genus Loxostege.

Biological group.

Polyphagous pests.

Morphology and biology.

Adults of the Beet Webworm are characterized by sexual dimorphism: males are smaller in size than females (male wing 18-20 mm, female wing 20-26 mm); males have thinner and longer abdomen than females; male antennae are serrate and female antennae are filiform. Life span is 4 to 20 days. Fertility varies from 3 to 300 eggs, maximum to 600 eggs. Eggs are laid on lower side of leaf, on sprouts and soil, either in batches (2-3 and more, sometimes to 20 eggs) or one by one. Development of eggs lasts 2-15 days. Larvae develop during 10-30 days depending on temperature and reach body length 35 mm at the last 5th instar. Larvae color is greenish to gray-greenish and black. One dark strip extends on the dorsal side and two dark strips on the lateral sides. Larval head is black with light pattern. Larvae feed on leaf and young growth. Larvae overwinter inside cocoons in the soil after finishing their feeding. Pupae vary in coloration (yellowish to dark-brown) and weight of body (12 to 60 mg). The pupal development lasts 7-38 days.


The Beet Webworm is widespread in Europe, Asia and North America. Mass outbreaks have been observed in Bulgaria, Romania, Austria, Hungary, Yugoslavia, Poland, Czech and Slovak Republics, Ukraine, Moldova, Mongolia, China, Iran, Turkey, Canada, Russia. In Russia it is widely distributed in steppe, forest-steppe, and southern taiga zones.


One generation develops in Non-Chernozem zone, two generations occur in forest-steppe and northern steppe zones, Siberia and the Far East, but to three or four generations may take place in southern steppe zone, the North Caucasus, Transcaucasia, North Kazakhstan. Adults fly during different periods depending on a zone, and their flight is frequently extended; adults of the winter generation fly in May and June, imago of the first generation fly in June and July, moths of the second generation fly in July and August, and of the third-fourth generations in August and September. For the beginning of oviposition females need nectar. In their search for places suitable for nutrition and oviposition the adults are capable to fly dozens of kilometers. Insect development depends on temperature and precipitation during larva nutrition, pupa development and moth oviposition (optimum Hydro-Thermic Coefficient is 0.9 to 1.7). Hibernating larvae survive easily after long-term periods of very low winter temperatures up to -40°C. Insect population may depend on activity of entomophages (parasites and predators) and also entomopathogens. Larvae feed on wild-growing plants. Third-instar larvae begin to feed on cultural plants in case the weeds are dead.

Economic significance.

Displays its harmfulness in the periods of population increase and mass reproduction that usually occur every 10-12 years. It tends to 60% yield reduction, sometimes causing 100% plant destruction; economic threshold is about 10 larvae per 1 sq. m. The greatest damage puts to sugar beet as well as perennial fabaceous (beans), sunflower, pea, hemp, maize, vegetable plants; it is capable to injure barley, wheat, sorghum, potato. This insect infests more than 200 species of wild-growing plants. Control measures: deep under-winter ploughing, interrow soil treatment, loosening with hilling, spring harrowing in the cocoon sites especially; insecticide treatments of plants during the period of larval development and let of Trichogramma spp. parasites; application of biopreparations, such as Lepidocide and Bitoxibacillin.

Related references:

Alekhin V.T., Kuznetsova T.L. 2003. The Beet Webworm and control measures against it (Recommendations). Moscow: FGNU "Rosinformagrotekh". 76 p. (in Russian).
Fal.kovich M.I., Martin M.O. 1999. Family Pyraustidae - widewing moths. In: Insects and mites - pests of agricultural crops. V. III., part 2. Lepidoptera. St.-Petersburg: Nauka, p. 167-170 (in Russian).
Knorr I.B., Gorbunov N.N. 1995. Bioecological principles in methods of revealing, registration, forecasting and control measures against the Beet Webworm in Siberia (Recommendations). Moscow: Tsentr nauchno-tekhnicheskoy informatsii, propagandy i reklamy. 38 p. (in Russian).
Kuznetsova T.L., Smirnova M.P. 2002. Methods of the Monitoring Beet Webworm. In: Monitoring and forecasting methods of pest development. Moscow, St.-Petersburg. P. 18-27 (in Russian).
Tribel S.L. 1989. The Beet Webworm. Moscow: VO "Agropromizdat". 64 p. (in Russian).

© Kuznetsova T.L., Chumakov M.A.

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