W. E. Mitchem
Orchard and Vineyard Floor Management
NC State Univ., Clemson Univ., Univ. of Georgia, Cooperating
Herbicides formulations containing glufosinate are now cleared for use in stone fruit crops. For years glufosinate has been registered for non-selective postemergence (POST) weed control in apple, grape, and blueberry plantings and now those formulations of glufosinate (Rely 280, Reckon, Surmise, and possibly others) with fruit uses on their label have been expanded to include stone fruit crops.
Glufosinate has a lot to offer as a non-selective POST herbicide that stone fruit growers will find beneficial. For beginners it will control glyphosate resistant weeds that are fairly common in the peach production areas of the Southeastern United States. It also offers control of species that paraquat has difficulty controlling like horseweed, curly dock, wild lettuce, and plantain. Glufosinate product labels also list blackberry species, hemp dogbane, and poison ivy as being controlled. One significant advantage glufosinate has over glyphosate relates to peach tree sensitivity. Glufosinate is not as systemic as glyphosate and lacks the ability to be translocated to the roots of peach trees. However, glufosinate is “locally systemic” meaning it can move out of leaf tissues, down leaf petioles making it more effective on species paraquat has difficulty controlling.
Rely 280, Reckon, and Surmise are three formulations of glufosinate containing 2.34 lb ai/gal that has stone fruit on their label. The use rate for these formulations in stone fruit is 48 to 82 fl. oz/A per application. The total amount allowed to be used within a 12 month period is 164 fl. oz/A, and there must be a minimum of 28 days between applications. Glufosinate has a 14 day PHI. Only trunks with callused, mature brown bark should be contacted by glufosinate unless the trunk is protected with a non-pourous wrap, grow tube, or waxed container. Glufosinate contact with green bark, stems, or foliage of desirable plants will be injured. Glufosinate formulations contain adjuvant therefore additional additives like a non-ionic surfactant or crop oil is not needed. The addition of a spray grade ammonium sulfate fertilizer has enhanced glufosinate activity.