Influence of Pine Bark Substrate Age on Performance and Leaching of Nursery Preemergence Herbicides

Abstract

Additional index words. preemergence, postemergence, soilless substrate, pine bark, substrate age, ornamentalAbstract. The objective of these experiments was to determine if preemergence herbicides perform similarly across pine bark that was aged for varying lengths of time including 0, 4, 8, and 12 months after bark removal from harvested trees. Three preemergence herbicides were evaluated for three separate weed species, including 1) Cardamine flexuosa With. (bittercress) with isoxaben, 2) Digitaria sanguinalis (L.) Scop. (large crabgrass) with prodiamine, and 3) Oxalis stricta L. (woodsorrel) with dimethenamid-P. Leaching of herbicides through substrates was evaluated for prodiamine. Weed growth in the various substrates was variable, but few differences were detected in weed growth among the pine bark substrates evaluated. For isoxaben and prodiamine, weed control was similar among the pine bark substrates in most cases when label rates were applied. Although some differences were detected in prodiamine performance across different pine bark ages, a high level of control was achieved in all cases at rates well below manufacturer recommendations. Prodiamine leaching was minimal in all substrates. It would be recommended that growers test substrates for physical properties before use so that irrigation and other production inputs could be modified if needed. In most cases, growers should expect similar performance of preemergence herbicides regardless of pine bark substrate age.

Short-term Preemergence Herbicide Adsorption by Mulch Materials and Impacts on Weed Control

“…Only 10% to 30% of the herbicide that was applied reached the substrate surface, at least initially following only %1.5 inches of irrigation over a short period, which is similar to previous findings (Banks and Robinson, 1982;Crutchfield et al, 1986;Dao, 1991). Although it is possible that herbicides leached downward beneath the 1-inch depth used for chemical analysis, this would be unlikely given that these herbicides are generally adsorbed tightly to PB substrates (Stewart et al, 2019). Only 1.5 inches of irrigation was applied over a short 3d period in this study, and none of the evaluated herbicides would be expected to leach deeper than based on previous reports (Derr et al, 2015;Jhala and Singh, 2012).…”

“…Conversely, dimethenamid-P is characterized as having a higher likelihood of leaching due to greater solubility and lower K oc . Pendimethalin and prodiamine leaching have been shown to be minimal in PB substrates (Simmons and Derr, 2007;Stewart et al, 2019). However, a greater void space in a mulch material compared with the previous studies with PB growing substrate is likely to cause more downward movement (Simmons and Derr, 2007), leading to a recovery of 12% Mulch applied at a 2-inch depth was removed from containers before sowing weed seeds at 3 d following preemergence herbicide applications and 1.5 inches of cumulative overhead irrigation; 1 inch = 2.54 cm.…”

PRE and POST control of Praxelis clematidea, an emerging weed in Florida nursery production

“…Though data on indaziflam are lacking, top-dressing fertilizer has been shown to reduce the efficacy of prodiamine, oxyfluorfen þ pendimethalin, and dimethenamid, but the effect is often dependent upon weed species (Altland et al 2004;Stewart et al 2018). Furthermore, a higher percentage of peat moss in the substrate at Balm may have contributed to higher observed efficacy with dimethenamid, similar to previous reports by Stewart et al (2019) with yellow woodsorrel (Oxalis stricta L.). As praxelis seeds were obtained from different populations in Florida, differential responses could also be due to presence of biotypes that respond differently to herbicides--an issue that deserves further investigation (Kohler et al 2004;Waite et al 2013;Warwick 1991).…”

Pesticide Sorption to Soilless Media Components Used for Ornamental Plant Production and Aluminum Water Treatment Residuals

“…The specific chemical and physical properties of the pine bark substrates depend on the tree species, harvesting methods and season, and how and when the materials are processed. 46 Pine bark is derived from phloem, which consists of lignin, cellulose, polysaccharides, and a variety of other components. Lignin is a biopolymer of oxidatively coupled alcohols including: hydroxy-cinnamyl alcohol, coniferyl alcohol, sinapyl alcohol, and p -coumaryl alcohol.…”

“…The organic materials peat and pine bark are both derived from plant sources but differ in the degree of weathering with peat forming over thousands of years versus pine bark sources that are weathered for a few months to a few years. The specific chemical and physical properties of the pine bark substrates depend on the tree species, harvesting methods and season, and how and when the materials are processed . Pine bark is derived from phloem, which consists of lignin, cellulose, polysaccharides, and a variety of other components.…”