Ceutorhynchus rapae Gyllenhal Coleoptera Curculionidae

Natural History

Distribution. The cabbage curculio was likely introduced accidentally to North America from

Europe in the early 1800s. The earliest confirmed specimens were collected in 1873 in Massachusetts, but several writers described injury by a similar weevil earlier in the century. It is now generally distributed in the northern portions of the United States, extending as far south as Virginia in the east and California in the west. In Canada it is found from Ontario west to British Columbia.

Host Plants. Most cruciferous vegetable crops can be damaged by cabbage curculio, including cabbage, cauliflower, and turnip. Despite the common name, however, cabbage is one of the least preferred host plants. The beetles prefer wild crucifers such as hedge mustard, Sisymbrium officinale; pepperweed, Lepidium spp.; and shepherdspurse, Capsella bursa-pastoris; and then cultivated crucifers other than cabbage.

Natural Enemies. Natural enemies of cabbage curculio are not well known, but Euderis lividus (Ash-mead) (Hymenoptera: Eulophidae) has been reported to parasitize the larvae (Chittenden, 1900).

Life Cycle and Description. There is one generation per year, with the adult stage overwintering. In Maryland and Missouri, adults emerge from diapause in April. Mating and oviposition occur soon after emergence. Adults feed briefly on foliage and stems before oviposition, but cause little damage.

  1. Females deposit eggs in stem tissue within cavities created by feeding. Some swelling of the plant tissue near the eggs is noticeable. Oviposition is complete by early May. Eggs are elliptical and gray. Egg length is 0.65-0.85 mm; and its width is 0.350.45 mm. Eggs hatch in 5-8 days.
  2. The larvae feed in stem tissue. They are whitish, with a yellowish or brownish head. The body tapers markedly toward both the anterior and posterior ends. The body is fairly wrinkled in appearance, with no evidence of legs apparent. Larvae attain a length of 5-6 mm at maturity. The larval development requires about 21 days, and most of then have abandoned their feeding sites by the end of May.
  3. Larvae drop to the soil to pupate, secreting an adhesive material to form a small cell from soil particles. The larva remains in the cell for about 14 days
Cabbage curculio larva.
Image Adult Diapause Coleoptera
Adult cabbage curculio.

before pupation occurs. The period of pupation is an additional 21 days. The pupal cell is about 5 mm in length, only slightly larger than the white pupa. Pupation occurs at a depth of less than 2 cm. The adults emerge from their pupal cells in June and feed before entering diapause.

Adult. The adults measure about 2.70-3.25 mm long. The base color of the beetle is black, but the body is covered with a fine layer of scales that are brownish-yellow in new adults and gray in overwintered adults. The elytra are marked with longitudinal ridges, but the most distinctive feature is the elongate snout. The snout exceeds the thorax in length, and is curved ventrally under the body.

The biology of cabbage curculio was provided by Chittenden (1900).

Damage

The cabbage curculio damages crucifers by feeding as larvae in the stems and petioles of the plant. Young tissue is preferentially selected by ovipositing females, and she may deposit her eggs basally in a small plant, or just below the flower on a mature plant. Plants may show wilted leaves or breakage when larvae are numerous. Death sometimes occurs, especially among seedlings. Curculio feeding also seems to allow plant pathogens to gain entry.

Management

Cabbage curculio is generally considered a minor pest, and has little importance to commercial plantings. Foliar applications of insecticides readily control this insect. Because of their strong preference for weeds, adults often avoid ovipositing on crops, especially cabbage. If cabbage curculio is abundant, however, it is advisable to delay destruction of cucur-

bitaceous weeds until oviposition has occurred. Timely destruction of weeds by tillage provides an effective trap crop and an effective non-chemical means of insect control.

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