Controlling offsite movement of agricultural chemical residues can be a chronic headache for winegrape growers.

An article, in part published by the University of California Division of Agriculture and Natural Resources, provides winegrape growers with information on farming practices that can help reduce the occurrence of organophosphate and synthetic pyrethroid pesticides in surface water, including streams, lakes, ponds, rivers, and drainage ditches.

The 2014 article describes the regulatory approach to surface water protection; gives background information on the safe and effective use of pesticides, integrated pest management, and handling runoff water; and demonstrates a self-assessment of the potential risk of offsite pesticide movement, using flowcharts for specific management practices and field conditions in winegrapes.

The risk self-assessment focuses on issues that affect either the number of pesticide applications containing certain active ingredient, or the offsite movement of pesticides as drift, attached to sediment, or in water. The first part of the publication concludes with research-based management practices that mitigate the risk that pesticide residues will leave the application site and enter surface water.

You can read the article at https://bit.ly/2Mddaq4 

PERSISTENCE STUDY

Several years ago, another take on the situation was provided by the National Library of Medicine. The persistence of several common herbicides, from grapes to wine, was studied. Shiraz, Tarrango, and Doradillo grapes were separately sprayed with either norflurazon, oxyfluorfen, oxadiazon, or trifluralin-persistent herbicides commonly used for weed control in vineyards, according to the report. The dissipation of the herbicides from the grapes was followed for 28 days following treatment.

Results showed that norflurazon was the most persistent herbicide, although there were detectable residues of all the herbicides on both red and white grapes at the end of the study period. Penetration of herbicides into the flesh of the grapes was found to be significantly greater for white grapes than for red grapes.

Small-lot winemaking experiments showed that norflurazon persisted at levels close to the initial concentration, on through vinification, and into the finished wine. The other herbicides degraded, essentially via first-order kinetics, within the period of "first fermentation," and had largely disappeared after 28 days.

The use of charcoal, together with filter pads, or with diatomaceous earth, was shown to be very effective in removing herbicide residues from the wine. A 5 percent charcoal filter removed more than 96 percent of the norflurazon persisting in the treated wine.

The National Library of Medicine’s website is https://www.nlm.nih.gov/