New Research Concerning the Impacts of Glyphosate on Orchard Crops
Glyphosate is a well-known and commonly used herbicide for weed management in orchards. In the later 2000s, some researchers suggested glyphosate use in orchards could lead to soil nutrient deficiencies and, if the pesticide accumulated in the soil, have a direct impact on the trees. Because of the concerns this raised, Drs. Brad Hanson and O. Adewale Osipitan conducted a long-term research project from 2013-2020 to determine the impacts of glyphosate on orchard crops.
The “Impacts of repeated glyphosate use on growth of orchard crops” was published online in August 2020 where it can be read in its entirety. The research project experimented on almond, prune and cherry trees by applying glyphosate three times each year between April and November. Dosages ranged from 0 – 4 lb ae/A equivalents, and were applied to a 6’ x 6’ area around each tree.
To measure the effects of glyphosate, leaf samples were collected every 14 days after each application during the first year of treatment. Chlorphyll content was measured in leaves 30 days after each application during the first two years of the research. Trunk diameters were taken at the start of the project and each subsequent winter. After the 6th and final year, leaf samples were again collected for nutrient measurements.
According to the researchers, shikimate levels (which would indicate direct herbicidal effects from glyphosate) were similar among treated and non-treated trees indicating little or no direct effect of the herbicide on these trees even at extreme application rates (4 lb ae/A). Likewise, the chlorophyll content of the leaves gave no indication of differences among the treated trees. Overall, the leaf nutrient analysis undertaken at the close of the study provided no evidence of a negative impact of glyphosate on the orchard crop’s nutrient status, nor was trunk diameter negatively affected.