Description of the Pest
Adults of the clover root curculio are slightly smaller than alfalfa weevil adults and are a mottled gray-brown with no distinct patterns. The grublike larvae are white and feed on alfalfa roots during the spring. The larvae can be difficult to find because they are in the soil and often may be inside the root nodules during early instars. The life cycle is similar to alfalfa weevil in that the adults leave the alfalfa fields and spend the summer in protected areas. There is one generation per year.
The clover root curculio is a recognized alfalfa pest in most U.S. growing areas, but information on this pest in California is limited. Clover root curculio is most likely to be found in June and is apparently more common in sandy soils than in the heavier soils.
Damage
The damage is usually observed as patches of poor growth or stand decline because the larvae gouge, even girdle, the taproots. The gouges can be a point of entry for root rot diseases. This damage has been shown to be detrimental to alfalfa yield and stand longevity in the eastern United States. Damage has also been reported in California, but the severity and distribution of damage in the state has not been assessed.
Management
There are no thresholds or control measures for this pest. Crop rotation to non-legume crops is the best way to manage this pest. There are no insecticides registered for clover root curculio larvae.
Cultural Control
Rotate out of alfalfa and other legumes for at least one year. Avoid planting alfalfa next to infested fields (since seedling roots are weaker and more susceptible to feeding damage). Provide good irrigation and fertilization to prevent plant stress that might make stands more susceptible to decline. Clean equipment when moving between fields.