Yellow nutsedge, Cyperus esculentus, spreads and reproduces primarily by 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 12 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; nutsedge tubers will often spread from one field to the other fields. 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 plastic mulch as the nutsedge shoots punctures the mulch and grow through it. To prevent this, dense materials such as water-resistant paper or recycled paper between two layers of standard plastic mulch or other weed barriers can be applied to bed tops to stop or greatly reduce shoot penetration through the plastic mulch throughout the season. Steam application has shown very good control of yellow nutsedge, but follow-up hand weeding may be necessary to eliminate nutsedge plants that may germinate from surviving tubers.
Nutsedge tubers can remain viable for about three years. Fumigation with chloropicrin or a mixture of 1,3-D and chloropicrin does not provide complete control of nutsedge. However, use of barrier films like VaporSafe with 1,3-D plus chloropicrin 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 inland locations compared to the cool coastal zones. 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 before they reach the 5-leaf stage to prevent new tuber formation. Tubers are easily spread in soil on farm equipment that has worked on infested areas. Nutsedge infestations usually do not get established in properly fumigated strawberry fields.
Sowthistle, Hairy Fleabane, Horseweed, Everlasting Cudweed, and Common Groundsel
Weeds with wind-dispersed seeds such as sowthistle, hairy fleabane, horseweed, everlasting cudweed, and common groundsel can move into the field at any time during the production cycle. Control weeds with wind-dispersed seeds in and around your field. Preplant herbicides such as flumioxazin, pendimethalin and oxyfluorfen are effective in managing these weeds. Pay particular attention to efficacy if glyphosate is used in adjacent areas, since horseweed and fleabane can be resistant to glyphosate. Due to labor for hand weeding, management is difficult in-season.