Paraquat is rainfast in record time

Weed control operations with paraquat in a tea plantation: is it going to rain? Paraquat controls weeds effectively even if it rains within 15 to 30 minutes of spraying. This excellent rainfastness is unique amongst herbicides and gives farmers important practical benefits. More work can be achieved in between showers and weed control will be better than when using alternative herbicides such as glyphosate or glufosinate and surprised by unpredicted rainfall.  In tropical rainy seasons, as elsewhere, sudden rain can wash recently applied foliar-acting herbicides from weed leaves reducing or eliminating their efficacy. Using simulated rain, paraquat was found to be rainfast within 15 minutes of application, ie no difference could be measured between the degrees of weed control with or without wash-off. Clearly, sufficient paraquat must have been absorbed within that short time for maximum efficacy. However, glyphosate and glufosinate gave poor weed control even when the rain-free period was six hours. Not only is paraquat absorbed into weeds very quickly, but it is very fast acting. This allows any decisions on re-spraying to be made probably within a day of any problems. With slow acting glyphosate, the likely level of control would not be obvious for several days or even a few weeks depending on temperature. Read more ...