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This publication covers chemical weed control and weed response to a variety of crops.
Annual and perennial grasses can be selectively controlled in most broadleaf crops and landscapes using postemergence herbicides that control only grasses -- chemicals often referred to as “postemergence graminicides”. There are four graminicides labeled for use in horticultural crops – fenoxaprop, fluazifop-p, sethoxydim and clethodim. Each graminicide is systemic (translocated) and has short-term soil residual (about 2 weeks). Although each herbicide kills grasses in the same way (acting upon the same site of action), they differ in their effectiveness on grass weeds, safety on crops, and labeled uses.
When it comes to weeds, “start clean – stay clean” should be the moto of every nursery manager. This is especially true for producers of herbaceous perennials. Although we can control most grassy weeds with postemergence herbicide; otherwise, we have few herbicides to use when weeds get out of hand. Furthermore, the herbicides labeled for use in herbaceous ornamentals are either safe on many ornamentals and do not control many weeds, or control lots of weeds but are safe on only a few ornamentals. Consequently, to manage weeds effectively a comprehensive nursery weed management program including exclusion, sanitation, preemergence herbicides, some postemergence herbicides and hand weeding will be needed.
Supplemental hand weeding accounts for the majority of landscape bed maintenance costs. When used exclusively, it can cost 10 to 100 times as much as an effective herbicide or mulching program. However, many of the costly and unsightly weed problems can be avoided or at least minimized with a little planning. Developing a landscape weed management plan involves five basic steps.
This factsheet provides information about control strategies for dealing with common ragweed, particularly for Fraser fir production operations.
How often are you weeding? Is it frequently enough to prevent the next generation of weeds? Many of the most common weeds of container nurseries flower and produce seeds within 30 days. Our research suggests that you should be removing emerged weeds every 2 to 3 weeks. This publication offers information on some common container weeds.
This table presents information on preemergence herbicides for herbaceous ornamentals.
This publication covers the identification and control of Florida betony, an aggressive, rhizomatous perennial in the mint family categorized as a category B noxious weed in North Carolina.
This chart presents the grams of herbicide needed for circular landscape beds of various diameters.
Phoma macrostoma, a potential biocontrol agent for turfgrass weeds, was isolated from Cirsium arvense plants in Canada and is being tested in other regions of North America for control of broadleaf weeds in turf. This research was conducted to investigate the effects of varying temperature conditions on Phoma macrostoma control of seedling broadleaf weeds. Experiments were conducted in growth chambers to compare the efficacy of three doses of Phoma macrostoma on two species, Senecio vulgaris and Lamium amplexicaule grown in 4 temperature regimes – 15/20, 20/25, 25/30 and 30/35°C (dark / light period) temperatures. These data suggest that high temperatures common in the southeastern United States should not be an impediment to activity of Phoma macrostoma efficacy, and may actually improve the control of some broadleaf weed species.
This table presents information on preemergence herbicides registered for use on woody ornamentals.
