We receive requests for information on “organic” alternatives to glyphosate (e.g., Roundup), especially for “trim” sprays on paved areas, sidewalks, skin surfaces on ball fields, etc.
The research on organic non-selective herbicides that are being marketed as replacements to glyphosate (for example, Roundup) is growing but it is much more limited that what you can find on more conventional herbicides; however, we have been evaluating some products. Our results indicate that these alternative products are short term “burn-down” products that have the ability to kill small immature plants. On the other hand, large perennial plants, while looking sick to dead soon after being spray, start to re-grow a week or so after being sprayed.
Therefore, we only recommend these alternative products for “trimming” applications on immature (very young, small plants vegetation. These products will be very disappointing if you practice an infrequent “trim” spray schedule (once or twice a year) that is treating a mixture of young and old plants. The immature plants are likely to die but you will find that the large perennial plants will survive and continue to grow once the product’s burn-down effect wears off.
Experience indicates that these burn-down products are best used on paved areas, sidewalk cracks, etc. starting early in April when weeds are very small (immature). Additionally, these products will need to be re-applied at a frequency that matches the environmental conditions which stimulate emergence of new weeds. In other words, you cannot “wait to treat later on”; every time the weather stimulates emergence of new weed, you need to re-spray. This requires more labor for routine scouting and monitoring of sites to determine when and how often to apply the product(s).
The managers that I know using this approach to control weeds in paved areas, sidewalks, etc. often prefer the clove oil based products (Matran 2 and BurnOut are two examples). These products can generate complaints about the order (strong smell of clove) and you need to be wary of slipperiness caused by oil-based products on smooth surfaces such as cobblestone walkways etc. You are also likely to spend more on these products compared to glyphosate. These products typically have a greater expense; you need to use more product (more per application and more applications per year) and allocate more labor to this work.
If interested, you can download a short (3-page) pdf from the URL below for more information on the general topic of low-impact “pesticides” http://turf.rutgers.edu/newsandevents/lowimpactpesticides.pdf.