Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 30, 2008
Publication Date: July 1, 2008
Citation: Hanson, B. D., Schneiderr, S. M.. 2008. Evaluation of Weed control and Crop Safety with Herbicides in Open Field Tree Nurseries. Weed Technology. 22:493-498. Interpretive Summary: Fruit and nut tree nurseries currently rely on preplant soil fumigation with methyl bromide, tillage, and hand labor for weed control. The phaseout of methyl bromide and increasing fuel and labor costs suggest that herbicides will become more important weed management tools in perennial crop nurseries. These studies were initiated to determine the weed control efficacy and tree crop safety of preplant and post emergence herbicide treatments in stonefruit nurseries. Preemerge applications of oryzalin and dithiopyr provided acceptable weed control with no crop injury while several other preemerge applications severely injured the emerging peach rootstock. Several of the injuries preemergence treatments were much safer when applied after crop emergence. Additional research is needed on herbicides and application techniques to provide California growers management tools for control of problem weed species in fruit and nut tree nurseries.
Technical Abstract: Open field production of fruit and nut tree nursery stock depends upon preplant soil fumigation, extensive tillage, and hand labor throughout the growing season for adequate weed control. Because methyl bromide, the favored fumigant, is being phased out due to environmental concerns and the costs of both fuel and labor continue to rise, herbicides are likely to become a more important weed management tool in the tree nursery industry. Two trials were conducted to evaluate weed control and crop safety with several herbicides applied following fumigation with methyl bromide or 1,3-dichloropropene in central California stonefruit nurseries. PRE and POST-directed applications of several labeled and unlabeled materials were applied in a band over seeded peach rootstock or applied after emergence with a drop-nozzle spray boom. Crop productivity and weed control were monitored throughout the one year growing season. PRE oryzalin and dithiopyr treatments provided the best weed control with very little crop injury. PRE applications of flumioxazin, rimsulfuron, and sulfentrazone did not have adequate crop safety at the rate and timing tested. However, POST-directed applications of flumioxazin and rimsulfuron were much safer to the peach/almond crops and should be evaluated in future trials. Additional herbicides and application techniques are needed to find acceptable, safe control of weeds such as California burclover, common mallow, and redstem filaree, which often are poorly control with preplant fumigation in tree nurseries.