March 2016. The recent news that Glyphosate may be associated with cancer (“probably carcinogenic”) caused a number of members to write with suggestions of alternative herbicides. Here is a list of comments from Palau; they describe if the product is “effective”, not necessarily that it was cost-effective compared with glyphosate or another product:
Steam, hot water, iced water and flame work well on broad leave weeds. These methods are not effective on weeds with underground tubers and rhizomes, e.g. Palau’s farmer identified worst weed: purple nutsedge.
Household strength vinegar was not effective. Commercial strength vinegar works well and may need repeated applications on stubborn weeds. You can make your own vinegar from produce rejects, waste and residue. Fruits such as spoiled bananas work well.
Alcohol also works well and may need repeated applications on stubborn weeds. You can make your own alcohol from produce rejects, waste and residue. Fruits such as spoiled bananas work well. You will need to distilled the alcohol to increase its strength.
For pre-planting, tarping works fine if you have the time and are not in a hurry. Tarping is placing a tarp over the plot and weighing down and sealing the tarp.
For pre-planting, solarization works fine for living plants. It does not work on some weed seeds and actually encourages some heat/moisture triggered weed seeds. Check if some organic standards do not permit solarization.
Seawater reduced to 50% of the original was effective. It’s use should be moderate. We suspect overuse in areas with low rainfall may lead to salt build-up.
Mineral oil, Plant oils, fats, and fatty-acids were effective. Coconut oil worked, its limitation are getting the proper strength. The temperature and the sun’s intensity directly effects coconut oils effectiveness. Pine oil has been sold as a herbicide. Perhaps pine oil is made or can be made in Fiji. Essential oils you distilled yourself would probably work well and are sold commercially as herbicides normally at 3% solution. Vegetable [cooking] oils may be tainted with GMOs.
Urine, chicken manure and other organic forms of nitrogen are placed before planting in high [weed killing] concentrations. You will need to wait until the field ‘cools down’ before planting. This method needs a good sense of judgment, high resources and time.
Mulches of eucalyptus and acacia lessened weeds; however, the mulch will lessen the growth of some plants. It is not recommended.
Living mulches of precocious plants and/or native ground covers and/or ‘smothering’ plants reduce weeds, e.g. mimosa, wild beans, dense plantings of sweet potato, stylo, sword bean, single leaf clover. If mimosa is used you definitely need to pull out or cut the root before it seeds. Some farmers use weed whackers to control living mulches.
Extracts from citrus – seeds and skins contain the highest concentration of the chemical which harms/kills weeds and quite a few other pests. There are commercial citrus derived herbicides on the market. I suspect extracts of lemon grass may be used as herbicides, especially the oil.
Baking soda, potassium bicarbonate and other sodas have worked. Potassium bicarbonate is better as there is no likelihood of sodium build-up. It is more expensive and harder to find in Palau than baking soda.
Chlorine bleach solutions are effective at killing weeds. It is not recommended as its collateral kills are to us unacceptable.
Other suggestions were:
Electricity, e.g., https://www.youtube.com/watch?v=sDzpC9Gl034, or for smaller plots, http://www.dailymail.co.uk/news/article-2090021/Weedinator-The-new-pesticide-free-way-clear-garden-But-beware–packs-volts-electric-chair.html. And a reminder manual removal, mulching, biological controls are also to be considered.