Pest Management Guidelines
Special Weed Problems
(Reviewed 1/09, updated 9/12)
SOWTHISTLE, LITTLE MALLOW, and NIGHTSHADE
Sowthistle, little mallow, and nightshade are annual weeds that are difficult to control in carrots. The registered herbicides will not control these weeds very well. Avoid growing carrot crops in fields known to be heavily infested with these weeds.
Nutsedge is a serious weed in spring- and summer-planted crops. Yellow and purple nutsedge are perennial weeds that reproduce from underground tubers, which can survive for several years in the soil. Each tuber contains several buds that are capable of producing plants. Only one bud at a time germinates to form a new plant; however, if that bud is destroyed by cultivation or an herbicide, then a new bud is activated. Control is best achieved by continuous cultivation during a summer fallow period or by rotating to crops where effective herbicide and cultural control methods can be used. For fall-planted carrots, plant after October 15 to avoid serious yield loss in carrots from competition by nutsedges. Glyphosate and metam sodium provide partial control prior to planting. Linuron and S-metalachlor provide partial control of yellow nutsedge during the production season.
UC IPM Pest Management Guidelines: Carrot
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