Agriculture Reference
In-Depth Information
effectiveness in suppressing weeds. The commercial products marketed as
organic herbicides performed better, and a solution containing 20 percent
acetic acid provided the greatest and longest -lasting control. Young annual
weeds were killed readily. Quack grass was suppressed, but it continued
to regrow, and the 20 percent acetic acid had to be applied three times
to effectively suppress the quack grass. In contrast, a single application of
glyphosate (not allowed in organic production) provided effective control of
even quack grass throughout the season.
When comparing products, the authors of the study concluded that or-
ganically acceptable acetic acid products cost around $40 per 1,000 square
feet of area treated. If three applications are needed, the cost rises to around
$120 per year. Conventional growers can achieve equivalent or better con-
trol by using a single application of glyphosate herbicide for about $13.
Even household vinegar (5 percent acetic acid) can irritate eyes and res-
piratory systems, so products containing 20 to 25 percent acetic acid must
be used with great care. Like soap and citrus oil products, acetic acid herbi-
cides kill succulent green tissues and are probably best used for spot treat-
ments within an orchard.
Citrus Products
Several citrus products are approved for use as herbicides in organic crops.
These products, some of which are on OMRI's approval list, are based on
various forms of limonene (citrus oil). These materials are effective degreas-
ers. They act by dissolving oils and waxes in the epidermal layers of plants,
causing those plants to desiccate (dry out) and die. To be effective, the ma-
terials must be sprayed on succulent green tissues. They can quickly kill
green tissues (within about two hours of application) and are most effective
against young annual and perennial plant seedlings.
Citrus products are not effective against established perennial weeds,
such as Canada thistle or quack grass, because the oils do not kill the roots,
rhizomes, or other underground organs that produce new shoots when the
tops are killed back. These products can damage young trunks and stems, fo-
Search WWH ::




Custom Search