Herbicides Take Longer in the Cold 

In cool winter months’ weeds grow more slowly and herbicides tend to take longer to take effect. Weed Weapon products are fast-acting but you should be a little more patient in winter.

One of the active ingredients in Weed Weapon (Extra Strength, Rapid Action and Weed Weapon Long Term) is glyphosate, which works by absorption into leaves and movement into the sap and to the growing points in both shoots and roots. Glyphosate blocks the pathway producing protein and causes a slow death by starvation. For best results, there is a requirement for sufficient healthy leaf tissue to absorb the spray and 1-4 hours’ dry time after application to allow uptake. This means that perennial weeds which go dormant and lose their leaves e.g. thistles and nettles are not effectively controlled with glyphosate alone over winter. The second active ingredient in these Weed Weapon products, saflufenacil, improves the performance of glyphosate and has its own mode of action; working on the green tissue of plants to block photosynthesis. It should, however, be expected that in winter the effects of Weed Weapon will take longer than in warmer, sunnier times of the year. But they will work on weeds that glyphosate only may not and they will work faster.

In general, you should expect:

• Weed Weapon Rapid Action to show effects on weeds within 7 hours in winter and 2 hours in warmer seasons.
• Weed Weapon Extra Strength to show effects on weeds within 1 week in winter and 2-3 days in warmer seasons.
• Weed Weapon Long Term to show effects on weeds within 1-2 weeks in winter and 2-3 days in warmer seasons.

Note: these timings are very dependent on the weeds, the part of New Zealand you are in and the temperature and sunshine conditions. Full death may take up to 3-4 weeks.

David Brittain
Kiwicare