A STUDY OF APPLE TREES EXPOSED TO THE FUNGICIDE AZOXYSTROBIN AND MIXTURE INTERACTIONS WITH SURFACTANTS

Abstract

A study was conducted to evaluate effects of the chemical Azoxystrobin on apple trees. Previous reports have shown that this commercial chemical is highly toxic to certain varieties of apple trees. Farmers in Northwestern Pennsylvania have reported to regulatory agencies that commercial apple trees are undergoing damage and have indicated that the cause is low exposure doses of Azoxystrobin from various sources. Results show that Azoxystrobin concentrations in the range of 100 parts per trillion and greater adversely affect trees when combined with a surfactant Damage, subacute lowest observable effect concentration, for azoxystrobin alone was shown to be around 10 part per billion. Azoxystrobin was obtained from a commercial spray tank previously used to employ this compound approximately two years ago. Sprayers tested from the local area were shown to have residue concentrations of Azoxystrobin sufficient to inflict damage to apple trees. Concentrations in contaminated sprayers ranged from <5ppm to 670ppm Azoxystrobin. A spray drift experiment demonstrated that with and without surfactant damage resulted on all leaves at distances of 250 feet. Comparison of apple blossoms in the suspect affected area with a control site suggests that plants exposed to low levels of this chemical exhibit greater blossom abnormality. It is hypothesized that damage from drift results to apple trees miles from the contaminant or emission source. Based on the finding of contaminated sprayers and that some products are currently being used which contain Azoxystrobin establishes the existence of a large number of non‐point sources for this chemical in Northwestern Pennsylvania. Apple trees have the ability to uptake this chemical through its roots (soil route) when the trees are early in their seasonal development. When trees are in later growth of the season, application of Azoxystrobin to soil did not appear to cause toxicity. Damage on leaves not treated with Azoxystrobin that emerged after application of this chemical to older leaves on the same branch indicates translocation. Study results demonstrate that use of compounds containing Azoxystrobin in general locations where apple trees or other sensitive plants are grown result in chronic toxicity from low dose exposures.