Field Guide     Pest Management     Clover Root Curculio

Clover Root Curculio

CROPS IMPACTED: Alfalfa, clover

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Family: Curculionidae

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About the Clover Root Curculio

Reproduction and Life Cycle

The clover root curculio overwinters as an egg or as an adult. The eggs that overwinter will hatch once spring comes. Any overwintering adults will emerge once the temperature reaches 50 degrees Fahrenheit. New larvae feed on the crown and roots of host plants; this stage of the clover root curculio is the most destructive to clover and alfalfa plants. It takes 3 to 5 weeks for larvae to complete their 5 instars. They then pupate in the soil with the adults emerging between June and July. It takes about 40 to 50 days for this pest to reach full maturity from the time it is first laid as an egg. As an adult, they do not cause significant damage, often just scratching up the edges of plant leaves. The adults will usually go into summer dormancy during the warmest period of summer. By the fall, adults grow active again and mate. The females lay their eggs in the ground near the base of host plants. If the weather grows too cold, females will hold off laying the rest of her eggs until the following spring, or during the winter if temperatures reach 50 degrees Fahrenheit.

Clover Root Curculio Identification and Habitat

Identification

The adult clover root curculio is a weevil that is dark in color, often brown to black. They have a sturdy body, about 3 to 5mm in length, and have a short, rounded snout. This pest is sometimes confused with the alfalfa weevil. To distinguish the two different pests, alfalfa weevils have a brown stripe running down its back, and a different snout shape to the clover root curculio. The eggs are extremely tiny, less than 1mm in diameter, and are off-white in its earlier stages, but will turn a glossy black after 2 to 3 days. Larvae are legless with a white body and brown head. They are stout and curved, reaching to be 6 to 7mm in length when fully mature. Pupae are 4mm and pale yellow in color.

Habitat

This pest is commonly found throughout the United States. While it prefers alfalfa and different varieties of clover plants, it has also been found on cowpeas, soybeans, and grass types. Especially in areas that are going through conditions of stress, this pest can cause a loss in forage, sometimes up to 35%. When the larvae feed on the roots (young larvae feeding on root nodules, and older larvae feeding on tap roots and fibrous roots), it reduces the plants strength, which is why when the plants are under stress, it can lead to death. If the plant does not die from the injury, it still reduces the plants quality and leaves the plant more susceptible to infection by different types of root and soil pathogens. These pathogens can cause plant wilt and root rot. The clover root curculio is also capable of carrying these pathogens with them, and can infect plants that have not yet been exposed. Therefore, while this pest may not directly cause the entirety of the damage to host plants, a combination of the root feeding by larvae and the pathogens can cause a noticeable decrease in stand longevity. This pest can be especially damaging to alfalfa seedlings if they are planted beside or near a field that already has a large clover root curculio population.

Clover Root Curculio Management and Control Methods

Cultural Control

To manage the clover root curculio through cultural control methods, use appropriate production practices. Do not plant new alfalfa fields in close proximity to old fields that have had a clover root curculio infestation. Also, plant alfalfa in the spring, compared to the fall, as the plants can grow vigorously while this pest is at the end of its egg laying period, meaning the plant will have enough time to become strong before they experience larvae attacks. Additionally, when larvae feed on roots, this affects the plants nutrient and water intake, so using effective fertility and irrigation management measures can increase the plants strength and help them to withstand injury. There are also natural predators that help to control this weevil, such as spiders and other ground beetles.

Chemical Control

There have been no insecticides known to effectively control the clover root curculio.

Latin / Alternative Clover Root Curculio Names

  • - Sitona hispidula

Sources

http://ento.psu.edu/extension/factsheets/clover-root-curculio

http://www.extension.uidaho.edu/forage/Fact%20Sheets/clover%20root%20curculio.pdf