Autumn is the season to keep an eye out for herbicide drift into vineyards
If weather conditions are conducive to spray drift while dryland farmers are spraying weeds, there is a risk of unintended/accidental spray drift into nearby vineyards.
Unfortunately, grapevines are extremely susceptible to damage from very low concentrations of 2,4-D or other growth regulator herbicides.
What to look for in autumn
Keep an eye out for symptoms associated with 2,4-D drift, on new growth or on leaves that were expanding at the time the vines were exposed.
- Distorted, fan shaped leaves
- Feathering or pointy tips on the leaf edge
- Blistered or puckered leaves
- Small narrow leaves with thick white veins
- Twisted or zig-zag shoot growth, and shortened internodes.
Note that wide sinuses and shortened, zig zag shoots may also be associated with nutrient deficiencies.
Some table grape varieties are more susceptible to 2,4-D than others, and you can also expect to see variable and intermittent damage within a patch, because spray drift can settle unevenly across a vineyard.
Do vines recover from 2,4-D spray drift?
Vines exposed to 2,4-D spray drift generally recover if the exposure is very mild.
Young vines are more susceptible to growth regulator herbicides than older vines.
If the exposure was mild, shoots may produce new, unaffected leaves from the axels of older, affected leaves. However, if the damage is severe, vine growth can be affected in subsequent seasons.
Action if your vineyard is affected by 2,4-D herbicide drift near harvest
- Straight after harvest, give the affected patch an irrigation and nutrition boost to encourage a strong flush of shoot growth. 2,4-D mimics a plant hormone and is readily transported from wherever the chemical was absorbed into new growth at shoot tips. Encouraging a growth flush will push the traces of chemical out to shoot tips and away from lignifying canes.
- Top the canopy before leaves start to sinesce (turn to autumn colours), to remove all new shoot growth. Herbicide that is drawn back into canes as vines prepare for dormancy can damage buds and early shoot growth in the following Spring. Removing new shoot growth prevents 2,4-D in those shoots being drawn back into canes or cordons.
ATGA strongly recommends that affected growers report incidents of 2,4-D drift to AgVic. Contact Jeff Scott at ATGA for more information.