From IPM in the South
By Rosemary Hallberg
Most of us are used to seeing weeds in our yards or flowerpots, but not in the plants that we buy in the store. Nursery crop growers and workers go to great lengths to make sure that the plants we buy are weed free when we pick them up. That service comes at a great cost to the grower, however, so Joseph Neal at NC State University sought to remove some of the burden by teaching nursery owners more efficient and economical ways to weed their container plants.
Weeds are a serious problem for nursery crop growers, not just because they reduce marketability of their container plants, but also because they can inhibit plant development. Just one large crabgrass plant in a container with Japanese holly, for instance, can reduce the weight of the holly by as much as 60 percent. Nursery crop producers use between three and six applications of preemergence herbicides per year, and often must still hard weed after that. The cost of hand weeding is between $500 and $4,000 per acre per year based on labor costs.
Research done by members of the Southern Nursery IPM Working Group showed that effective weed management started with an effective herbicide, followed by good sanitation practices and frequent hand weeding. The research was funded by a USDA Specialty Crop Block Grant through the North Carolina Department of Agriculture.
Using an herbicide that is effective for a particular weed, and applying the herbicide uniformly reduces hand-weeding costs by as much as 86%. Proper herbicide application involves correct calibration of equipment used to spread the granular herbicide.
Members of the working group conducted on-farm experiments and educational field days in North Carolina, Virginia and Florida to train growers on selecting the most appropriate herbicides, making more uniform herbicide applications and increasing the frequency of hand weeding, which actually reduces weeding costs by as much as 50% and reduces total weeding time as well.
In addition to the experiments and field days, the group conducted a webinar in April 2016 and prepared Extension handouts for agents and growers. The recommendations can also be found at https://weeds.ces.ncsu.edu/cost-effective-weed-control-in-container-nurseries/
Surveys conducted during the field days revealed that only 19 percent of attendees were calibrating their spreaders, but after learning the proper technique, half of them indicated they intended to adopt the method taught during the field day. Well over 50 percent said they would increase their weeding frequency.
Neal said that if those growers adopted those practices, which would reduce their hand weeding costs by an average of 36 percent, they would save about $818,720 per year in weed management alone.