Weed, herbaceous, control

Development of weed resistance to triazine herbicides has necessitated alternative weed control strategies. Rotation of triazines with other herbicides and combining triazines with other chemistries has been effective in ornamentals and Christmas tree plantations (Van Himme, 1989). Supplemental treatments in Christmas trees have been effective, using directed sprays of phenoxy herbicides or glyphosate before resistant weeds mature and produce seeds. Weed resistance from triazines is not a problem in most forest settings where the herbicide is applied only once or twice in a rotation, since 1 or 2 years of herbaceous weed control normally ensures survival and eventual dominance by conifers. When the conifer canopy closes, virtually all herbaceous vegetation is shaded out for some decades hence resistant weeds, if present, fail to survive from one generation to the next. 

Creighton, J.L., G.R. Glover, and B.R. Zutter (1986). Loblolly pine growth response to herbaceous weed control A summary of fifteen studies. Proc. South. Weed Sci. Soc., 39 193. 

Glover, G.R., J.L. Creighton, and D.H. Gjerstad (1989). Herbaceous weed control increases loblolly pine growth.. /. Forest., 87(2) 47-50. 

ATP and toxicity of adjuvants, 355-56 Aatrex for herbaceous weed control, 19-21... 

Metal Organics and Inorganics. The metal organic herbicides are arsenicals used for the selective, post-emergence control of grass and broadleaved weeds in cropland and noncroplands. These herbicides are particularly usehil for weed control in cotton and turf crops (2,296,294). CacodyUc acid is a contact herbicide used for nonselective weed control in cropland and noncropland (299). Ammonium sulfamate [7773-06-0] (AMS) is an inorganic herbicide used for control of woody plants and herbaceous perennials (2). 

Additional reasons to manage weeds in ornamental plants and conifer trees include fire protection, frost protection, rodent and disease mitigation, nutrient management, and aesthetics. Uncontrolled weeds and brush become serious fire hazards in the fall or early spring when herbaceous weeds are dry. Plantations of conifers have been lost because weeds were not controlled and fires started. Fires are less destructive when herbaceous vegetation is controlled. 

Triazine herbicides are primarily effective in controlling herbaceous weeds. A notable exception is the use of granular hexazinone for controlling woody invaders such as oaks (Quercus spp.) or aspen (Populus tremuloides) in conifer stands on medium- and fine-textured soils in the South or in boreal forests. Hexazinone also is used in the Maritime Provinces of Canada for controlling woody and herbaceous growth in natural Christmas tree stands (Townsend, 1995a). The impact of herbaceous plant cover is somewhat different from that of woody plant competitors, so control strategies on various forest conifer sites may differ. 

Table IX. Herbicides registered for controlling herbaceous weeds in young pine plantations in the southeastern United States.

The concept of controlling herbaceous weeds in pine plantations is relatively new. In most cases it is not necessary in order to establish a pine stand although early growth studies recently indicate that weed control can be very beneficial. As a result, herbicide technology for this purpose is just beginning to develop. More effective herbicides and application methods are currently being assessed through various university and industrial research efforts. 

TJicloram (4-amino-3,5,6-trichloropicolinic acid) is a herbicide used mainly to control woody plants and herbaceous weeds. This chemical is used to improve grassland or to maintain watershed and could contaminate surface water. Upon entering surface water, photochemical or microbiological processes are the most likely routes for picloram degradation. 

Introduction of a new broad spectrum post emergence herbicide class with utility for herbaceous perennial weed control. Proc. North Centr. Weed Control Conf. 26 64-68. 

A weed can be an annual, a biennial, an herbaceous or shrubby perennial, or even a tree species. This chapter introduces you to the way weeds work—how and why they are so efficient—and the range of organic methods you can employ to clear weeds and keep them under control. It is useful to be able to identify common garden weeds, especially perennials (see pp.80-81). Knowing how they reproduce, spread, and survive adverse conditions can help you to develop an effective control strategy. 

It is a broad-spectrum herbicide active both pre- and post-emergent. Studies with radiolabelled compounds ( ) show it to be rapidly translocated particularly to the meristematic regions. Translocation to the underground storage organs of perennial weeds prevents regrowth of these weeds. Most herbaceous and woody plants are controlled in the field at 0.4-1.0 kg a.e./ha whereas most woody plants require 0.7-3.0 kg a.e./ha (10). 

Burning—Fire may be used to control limited infestations of annual or biennial weeds. Fire destroys only the above-ground parts of plants and is nsnally not effective against many herbaceous perennial weeds. 

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