Taxonomic placing: Insecta, Holometabola, Coleoptera, Curculionidae.
Common name: Pea weevil, Pea and bean weevil.
Geographical distribution: Species of Sitona occur throughout the world. A dozen live in the Middle East, their distribution in the different regions is dependent on the abundance of the cultivated legumes. The more important species include Sitona crinita (Herbst), Sitona hispidula (Fabricius) (CIE Map #437), Sitona limosa (Rossi), Sitona lineata (L.) and Sitona lividipes (Fabricius).
Host plants: Various lentiles.
Morphology: The body of Sitona crinita is 3-4 mm long, covered with black and white setae, elytra with three rows of dark and white spots. The body of S. hispidula is 4-5 mm long, covered with black and white setae and the pronotum bears two light lines that are curved in front; a pale dot is located near each line. Sitona lineata is 4-5 mm long, its pronotum with two pale longitudinal lines, each elytron bears 5 gray bands. The body of S. limosa is about 5-7 mm long, brown with two white dots on its head. Each elytron with three dark-brown bands ornamented with light brown dots. Sitona lividipes is 4-5 mm long, dark, with a white band extending from the eyes to the posterior of the body. Its elytra are covered with pale lines and white dots. The larvae of all Sitona spp. are apodous.
Life cycle: All Sitona spp. raise only one annual generation. In the Middle East the active adults appear in autumn, at the rainy season. The females of S. crinita produce about 520 eggs, those of S. hispidula 720, S. lividipe 840, and S. lineata and S. limosa ca 1100 eggs. The eggs are placed on plants or on the soil, and require high (>75-80%) relative humidities for hatching. The emerging larvae move into the soil where they feed for 5-7 weeks on the plants’ root nodules and roots, pupating in the soil. The emerging adults undergo a summer diapause, which is terminated in the following autumn. Volatiles emitted by preferred host plants attract the adults to these plants. The weevils are long-lived, often lasting for several months.
Economic importance: The specific injury inflicted by the various local species of Sitona is difficult to differentiate. The adults feed on legume seedlings in winter, consuming part or all of the foliage. In spring the emerging larvae attack the nodules, disrupting the supply of nitrogen to the plants. Heavy pest attacks may result in serious losses. Sitona crinita is the most important pest of lentils in Syria. Sitona limosa transmits broad bean stain comovirus (BBSV) and broad bean mottle bromovirus (BBMV) to susceptible plants in Syria.
Monitoring: Aggregation pheromone traps are used for several species of Sitona.
Cultural methods: Sowing legume crops in spring may enable them to avoid most of the adult weevil damage. Growing legumes along with non-attacked plants can reduce overall damage. Rotating non-preferred crops, like oats, with legumes can have a similar effect.
Plant resistance: Resistance of lentils to Sitona crinitus is being developed in Syria.
Chemical control: Organophosphates and carbamates often provide satisfactory control.
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