ASHS 2025 Conference

With costs that can exceed $5,000 per acre, weed management is often one of the largest threats to container nursery profitability due to lack of postemergence herbicide options, need for labor intensive hand weeding, and the demand for weed free ornamentals. Due to high variability in nursery infrastructure, taxa being grown, and grower preferences, no one piece of herbicide application equipment is used at all nurseries in the ornamentals sector. For granular formulations, herbicides are applied with devices ranging from homemade hand-shaker jars, commercially available gravity-flow type hand spreaders, hand-crank hand-held spreaders (i.e. belly grinder spreaders or chest spreaders) and on a larger scale, tractor mounted granular spreaders. Costs for each of these application devices can vary widely and can have a significant impact on the accuracy, distribution pattern, and efficiency of the application, all which effect weed control and labor costs. For example, hand-shakers might be used to treat pots individually to reduce herbicide waste, that is, the herbicide landing outside of the pot during an application. This is a slower process but results in less non-target herbicide loss compared with a belly-grinder in which over 50% of the herbicide applied may not reach the target depending upon pot spacing. The L.E.A.P. (Labor, Efficiency, Automation, Production) team is currently working to evaluate, implement, and develop automation to increase the sustainability of the nursery industry. As part of this work, commonly used and commercially available herbicide application equipment is being evaluated for accuracy, distribution patterns, efficiency, efficacy and crop safety. Prior to initiation of this work, studies were conducted to determine most accurate method of measuring application equipment performance, specifically for granular applicators. Commercially available herbicide pans, plastic and glass plastic beakers, and small plastic funnels (5 cm diameter) with end caps were all tested in multiple different arrangements with 1 to 12 collection devices placed within blocks of nursery containers containing recently potted ornamentals in 3.8 L nursery pots. The use of the plastic funnels placed sunken in the potting substrate was determined to be the most accurate method, in which 82% to 120% of the target dose was captured across all four plant canopies and was the most practical method to implement as it could be used accurately regardless of canopy structure or pot spacing and is ideal for on-farm evaluations. Project was supported by LEAP Nursery Crops Toward Sustainability Award No. 2024-51181-43291.