Agricultural pest management
Special Weed Problems
(Reviewed 6/08, updated 6/12)
NUTSEDGES. Yellow nutsedge, Cyperus esculentus, spreads and reproduces primarily by perennial tubers. Purple nutsedge, Cyperus rotundus, occurs in areas with wet soil conditions. It is similar to yellow nutsedge, and management strategies are the same. Tubers of both species are formed on rhizomes that penetrate up to 8 inches deep in the soil. New plants begin to form tubers when they reach the 5-leaf stage.
Yellow nutsedge is most difficult to control in nonfumigated fields and buffer zones, which may also serve as a source of nutsedge development and spread into the field. Nutsedge grows actively in warm fall conditions and in summer-planted strawberries in southern California but becomes increasingly dormant with onset of cool temperatures in winter. Unlike other weed species, yellow nutsedge cannot be controlled by colored mulch as the nutsedge shoots make holes in the mulch and grow through it. To prevent this, a dense recycled paper can be laid on bed tops under plastic, which prevents shoot penetration through the plastic mulch until the paper layer deteriorates. The studies of durability of different paper types in combination with plastic mulches are currently under way.
Nutsedge tubers can remain viable for several years but usually are destroyed by soil fumigation with methyl bromide. Fumigation with chloropicrin or a mixture of 1,3-D and chloropicrin does not control nutsedge as effectively as methyl bromide. However, use of barrier films like VaporSafe with 1,3-D + Pic have been shown to improve weed control including nutsedge. Solarization of formed beds destroys many of the tubers that are buried no deeper than 3 inches. The technique may be more effective in hotter locations. Deep plowing to a depth of 10 or 12 inches with a moldboard plow that completely inverts the soil helps suppress infestations.
If nutsedge plants appear in strawberry plantings, remove them by hand cultivation before they reach the 5-leaf stage to prevent formation of tubers. Tubers are easily spread in soil on farm equipment that has worked infested areas. Nutsedge infestations usually do not get established in properly fumigated strawberry fields.
UC IPM Pest Management Guidelines: Strawberry
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