Field Guide     Pest Management     Vegetable Weevil

Vegetable Weevil

CROPS IMPACTED: Canola, vegetables, tobacco

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Family: Curculionidae

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About the Vegetable Weevil

Reproduction and Life Cycle

The vegetable weevil will have one generation per year, with the adults sometimes living over 2 years. This pest enters dormancy during the summer months in plant residue or trash along the field’s edge. When the adults emerge from the ground between January and June after overwintering, they will feed on the plants available to them, anywhere from 3 to 30 days. It is interesting to note that there are no males, only females; therefore, they do not need their eggs to be fertilized in order to reproduce. Females can lay hundreds of eggs throughout the fall season and into spring. They place their eggs in the soils surface, which is where they will hatch into larvae after about 14 days. The larvae only feed at night on young plants; they will stay in the ground while the sun is out. They remain larvae for 23 to 45 days, which is when they will pupate. The pupation stage of development will last 2 to 14 days, depending on the climate. Their entire development from egg to adult can take up to 4 months or as short as 1 month.

Vegetable Weevil Identification and Habitat

Identification

Vegetable weevil adults are about 8mm long snout beetles, are gray to brown in colour and have a lightly coloured spot that is in the shape of a V on its wing covers. These wings; however, are not capable of flight. Their eggs are oval, cream white, and about 0.5mm wide. They will turn to a black when they develop further. The larvae can grow to be about 12mm in length, are a yellow to green colour and have an orange to brown head. They have no legs and their body is curved. The pupa is a light yellow, turning to a brown as it matures. It is shaped closely to the body of an adult, being close to 8mm in length.

Habitat

This pest can be found in most areas throughout the world, as long as the climate is subtropical or has warm temperatures. Both the adults and larvae are attracted to numerous different vegetable crops, such as carrot, potato, turnip, lettuce, and tomato. They also feed on tobacco and several weed types. Specifically, they eat the buds, roots and foliage of the plants. This pest can have a big impact on a crops yield when they eat the seedlings, as this can stunt the plants growth and defoliation can occur which can kill the plant. This is why infestation early in the growing season when plants are young is the most damaging. When they eat folliage, they will leave behind unevenly shaped holes. Due to the fact that the adults cannot fly, it can take a while for new areas to become infested, often resulting in spotty damage within the field.

Vegetable Weevil Management and Control Methods

Cultural Control

If the infestation is limited to 1 row or area, it may be advised to destroy that area, or to go out when they are most active (during the night), and pick the weevils off of the plants. You can also use sticky barriers to stop the beetles from travelling to new areas if the problem is in your garden. For preventative measures, substitute host plants for non-host plants the next time you decide to plant in that area. Plant rotation can keep their population in check. Also, keep your gardens and fields weed-free and cultivate in the fall and winter. It is important to note that having satisfactory control is dependent on using an integrated management system that includes the use of cultural and chemical methods.

Chemical Control

Insecticides mixed with azadirachtin or pyrethrin can often provide sufficient control. Sometimes spot treatments are needed. The economic threshold to begin treatment is when at least 5 percent of young plants have been killed or wounded. When treating tobacco plants, use insecticides such as acephate, lambda-cyhalothrin, or lambda-cyhalothrin plus chloratraniliprole. Additionally, foliar insecticides that are put on your vegetable crops will also control the vegetable weevil. Be sure to carefully read the label for cautions and proper application.

Latin / Alternative Vegetable Weevil Names

  • - Listroderes difficilis

Sources

https://www.daf.qld.gov.au/plants/field-crops-and-pastures/broadacre-field-crops/integrated-pest-management/a-z-insect-pest-list/vegetable-weevil

http://www.ipm.ucdavis.edu/PMG/GARDEN/VEGES/PESTS/vegeweevil.html

http://ipm.ncsu.edu/AG271/tobacco/vegetable_weevil.html

http://www.ent.uga.edu/veg/solanaceous/vegweevil.htm