dc.description.abstract | Weed control is a continuing challenge for greenhouse, field, and container
nursery growers across the United States. Weed control techniques in container
grown ornamentals include hand pulling, herbicide applications, and utilizing
mulches. The practices each bring a unique challenge including labor costs
associated with hand pulling, herbicide non-target loss, herbicide resistant weeds,
and improper calibration of sprayers and spreaders.
Research has shown that wood-based mulches can successfully control
weeds both with and without addition of preemergence herbicides (Bartley et al.,
2014). The research presented addresses the effects of utilizing mulches in
combination with preemergence herbicides. By identifying preemergence
herbicides that work effectively with pine bark mini-nugget mulch, growers may be
able to increase weed control effectiveness and longevity in container grown
nursery stock. The research presented also addresses the effect of preemergence
herbicide application timing to pine bark-based mulches on weed control. The
objective of this research is to evaluate the weed control efficacy of three
preemergence herbicides, formulations of those herbicides, and herbicide
application timing in conjunction with 5 cm (2 in.) of a commercially available pine
bark mini-nugget mulch for control on long stalk phyllanthus (Phyllanthus tenellus),
spotted spurge (Chamaesyce maculata), or eclipta (Eclipta prostrata).
On 14 May, all containers were treated with the appropriate herbicide
recommended label rate either below or above 5 cm (2 in.) of a pine bark mininugget
mulch (Hood Landscaping Products, Adel, GA). Liquid herbicide treatments
included dimethenamid-P (Tower®; BASF Corp., Research Triangle Park, NC) +
pendimethalin (Pendulum® Aquacap™; BASF, Corp.) (1.7 kg/ha, 12.2 kg/ha) (1.5 lbs
ai/A, 3.3 lbs ai/A), indaziflam (Marengo® SC, Bayer Crop Science, Research Triangle
Park, NC) (0.08 kg/ha) (0.07 lbs ai/A), and flumioxazin (SureGuard®; Valent Corp.,
Walnut Creek, CA) (0.43 kg/ha) (0.38 lbs ai/A) and were applied using a CO2
pressure backpack sprayer at 30 gallons per acre. Granular herbicide treatments
also included dimethenamid-P + pendimethalin (Freehand®; BASF, Corp.) (1.7
kg/ha, 2.2 kg/ha) (1.5 lbs ai/A, 2lbs ai/A), indaziflam (Marengo® G, Bayer Crop
Science) (0.08 kg/ha) (0.07 lbs ai/A), and flumioxazin (Broadstar™; Valent, Corp.)
(0.42 kg/ha) (0.38 lbs ai/A) and were applied using a handheld shaker.
For all three weed species, weed count and fresh weight means were not
different when any herbicide was treated below or above an application of mulch.
Generally, shoot fresh weight and weed count were similar between all herbicidemulch
combinations and mulch alone containers. For most fresh weights and weed
counts of different placements or herbicides linear or quadratic trends increase up
to 30-60 DAT then steadily declined at 90, 120, and 150 DAT. This is thought to be
caused by shortened day length and the continuing depletion of available controlled
released fertilizer throughout the year. Indaziflam, liquid or granular, and liquid
flumioxazin consistently provided smaller shoot fresh weight and weed count that
either formulation of flumioxazin. | en_US |