California Avocado Commission — While it is often common practice for fruit growers to apply white latex paint to the bottom 2 to 3 feet of young, newly planted trees in order to provide some protection from herbicide drift, researchers note there is little evidence to prove this practice is effective.
A recent blog post by Dr. Ben Faber summarized the findings of a California field experiment conducted in 2017 that measured the impact of latex paint in preventing herbicide injury on young almond trees. The block of trees consisted of greenhouse-grown trees in cartons. Nine weeks prior to the herbicide applications, the cartons were removed for trees in the “no paint” and “old paint” sections so their bark could harden off. Two days prior to applying the herbicide, the cartons were removed for the “new paint” trees and then the trees were painted.
According to the researchers:
- The paint did not provide significant protection from glyphosate or glufosinate.
- Tree stress caused by trunk-applied herbicides was lowest in trees with no paint, suggesting that allowing the bark to harden on young trees is an important means of protecting them from herbicide drift.
- In most treatment combinations, old and new paint applications did not reduce tree stress as effectively as allowing the bark to harden on trees nine weeks prior to application.
- The most effective means of protecting trunks was installing a carton. However, it is important to remember that once the carton is removed (as the tree matures), there may be green bark present which would be vulnerable to herbicides.