Definition - What does Contact Herbicide mean?
Contact herbicides are chemicals that are sprayed onto the crop to kill the already present weed upon contact with minimal damage to the main crop, whereas systemic herbicides are absorbed through the root system. Grapevines are extremely sensitive to the application of contact herbicides which can injury the vine, affect future growth and permanently damage the leaf formations. It is important to avoid spraying contact herbicides during the early growing period in March – the bloom period in June, but spraying should be avoided until October.
WineFrog explains Contact Herbicide
Contact Herbicides kill weeds when sprayed directly to the plant parts and typically have a phenoxy-type (ether based) active ingredient. These types of contact herbicides are most widely used on agriculture crops, but grapevines are very susceptible to being damaged from this type of ingredient. Instead, a salt-based active ingredients are preferred for grapevines, or brands like Everest Union, Maverick and Achieve Avenge.
When spraying grapevines, it is very important to reduce chemical drifting by avoiding spraying during the vulnerable period, being aware of wind patterns or high pressure systems, environmental factors (like runoff) and water addition to make the chemical spray heavier and less likely to spread to other areas. Grapevines can also be exposed to drift from other farms or agricultural applications from miles away, so it is crucial to communicate with other agriculturalists when spraying contact herbicides. Most contact herbicides do not require a license to use, but home spraying without the consultation of a professional should be avoided, as these chemicals must be used with caution.