Various Weed Control Techniques in Container Nursery Production

Abstract

Studies were conducted evaluating selected herbicides during propagation of Loropetalum chinense ‘Ruby’ to determine effects on rooting and subsequent plant growth. Herbicides evaluated were: Gallery, Ronstar, and Regal O-O. Herbicides were applied in single applications during the propagation process: before sticking, lightly rooted cuttings, or fully rooted cuttings. Before sticking treatments were applied to flats filled with standard medium before cuttings were stuck. Once cuttings had 3 to 5 cm roots, the lightly rooted herbicide treatment was applied. The final herbicide treatment occurred when the cuttings were fully rooted. One year after sticking, growth indices of ‘Ruby’ Loropetalum were similar regardless of herbicide treatment. Ronstar applied before sticking and at lightly rooted suppressed root growth, while Regal O-O suppressed root coverage on all dates of application. Additional studies were conducted to evaluate the influence of alternative substrates on herbicide efficacy in container grown nursery crops. Substrates evaluated were either pine wood chips hammer-milled, whole pine trees chipped or hammer-milled, or the previously mentioned combined with pinebark. Rout and Ronstar were applied at recommended label rate. After herbicides were applied and irrigated, containers were overseeded with 25 spotted spurge (Euphorbia maculata) seed per container. With all of the substrates except whole pine tree chipped-hammer-milled to pass a 0.48 cm screen, the addition of commercially used pine bark resulted in less weed control (more weeds). Rout provided superior control followed by Ronstar and the non-treated control. These data show that control of prostrate spurge with commonly used pre-emergent applied herbicides may actually be improved with some of the alternative substrates currently being evaluated. Final experiments were conducted to evaluate non-chemical weed control options in containers. Pine bark mini-nuggets were evaluated as a non-chemical weed control technique for two weed species, Chamaesyce maculata (Spotted Spurge) and Eclipta alba (Eclipta). Seed (25/container) were directly placed on the potting substrate surface before mulching with pine bark mini-nugget mulch at 0, 0.5 in., or 1.0 in. Remaining treatments consisted of hand applying the pine bark mini-nugget mulch at 0.5 in. 1.0 in. on the potting substrate then overseeding spurge or eclipta. Results showed eclipta number per container were 87 % (1.0 in.) less 60 days after seeding and spurge fresh weight was reduced by 87 % (1.0 in.) compared to the non-mulched containers. These results, suggest that pine bark mini-nuggets can be used effectively for weed control in container nurseries with proper application.