Drew Wolter, UC Davis Graduate Student, Weed Science Program

Dani Lightle, UCCE Farm Advisor, Glenn, Butte, & Tehama Counties

(Excerpt from an article on the UC Weed Blog in November, 2019)

In order to prevent herbicide damage in young trees, especially from postemergence herbicide, standard pomological practice is to apply white latex paint to the bottom 2 to 3 feet of trunk of newly planted trees, before applying herbicides. While this may provide some level of protection, research to support this practice is lacking. In order to assess the efficacy of white latex paint in mitigating herbicide damage, a field experiment was conducted in Arbuckle, CA to evaluate the impacts of latex paint on herbicide injury in young almond trees.

Figure 1. The images above illustrate different levels of trunk gummosis observed in the field when comparing old paint (left) vs. no paint (right).

Preliminary results indicate that in most treatment combinations, old and new paint as trunk protection methods did not reduce tree stress caused by trunk-applied herbicides. Allowing the bark of young almond trees to harden off for at least nine weeks reduced herbicide damage. The most efficacious trunk protection option for young almonds trees is to install a carton, though remember when cartons are eventually removed green bark may be present and susceptible to herbicide injury. Therefore, as the trees mature and cartons are removed, allow the bark on trunks of trees to harden off to minimize herbicide damage.

To read the whole article, see the UC Weed Blog.