Monday, March 28, 2011

Spring 2011 Herbicide Drift

Dear FWWS Members,

We received the attached letter from the Washington State Department of Agriculture who asked that we forward it to our members. It contains important information regarding potential herbicide drift damage to those of you with vineyards and the ways in which you may be able to protect yourself from the economic damage. If you have any questions or require further information, please contact Bruce Olson at


Your FWWS Board

Attention Washington Grape Growers!

The Washington State Department of Agriculture (WSDA) requires your cooperation before we can assist you with an investigation. It is essential that the complexities of herbicide damage to grapes are understood by grape growers, as well as their need to adequately prepare appropriate information regarding their grapes prior to filing any complaint with WSDA personnel.

No one expects their crop to be exposed to herbicide injury, but it occurs, somewhere, every growing season. Damage from herbicide drift can cost a grower hundreds of thousands of dollars in crop loss, reduction of wine or juice quality, and serious harm to grape vines that can reduce future production. Traditionally, it has been phenoxy herbicides, such as 2,4-D, that have been responsible for the bulk of herbicide damage observed on grapes, but now more damaging chemistries are available for use in this region. Among them is a chemistry that interferes with nitrogen metabolism, thus rendering useless the application of water and additional nitrogen to herbicide affected vines.

It is of utmost importance that you fully understand both the quantity and quality of information required before a thorough and effective investigation can proceed through authoritative means, such as an investigation. WSU-FEQL and WSDA-PMD research has provided grape producers with the tools to provide critical and necessary data for any investigation’s proper procedure. Producer observations are management tools for critical decisions regarding irrigation, nutrition, and reliably reporting information to WSDA.

When an exposure to an herbicide occurs there is a critical lag time between the exposure event and the subsequent expression of symptoms. During this same time period perhaps hundreds of pesticide applications may have occurred that are similar or identical to the one affecting the grapes in question. Most critical herbicide exposures occur over a 12 week period beginning with bud break, but some may occur later in the growing season. It also must be considered that modern pesticides are rapidly metabolized by the affected plants and degraded in surrounding areas, thus making reliable laboratory analysis difficult or impossible to achieve. With this in mind, it is essential that WSDA personnel will only accept crop history data, from bud break onward through each leaf emergence (leaf indexing), which has been collected by on-site vineyard personnel.

Washington’s grape growing regions are not protected by isolation. Grapes are sensitive to many pesticides used to produce other crops both locally and throughout the agricultural region, including other states. WSDA strives to protect grape production through the restriction of phenoxy herbicides for use by only certified applicators and through various county rules that apply to nozzle/pressure use, daily start and stop times to avoid air temperature inversions, and more. Also bear in mind that many out-of-state based pesticide applicators working in Washington are unaware or avoidant of local conditions and/or state requirements, and pesticide applications which occur on Federal lands do not fall under WSDA purview.

It is necessary that growers realize and appreciate the enormity of evidentiary requirements faced by an investigator in any complaint scenario and the utmost importance of accurate and detailed information gathered by grape growers prior to filing a complaint. Failure to provide this required information to an investigator renders it impossible to proceed with a fair and accurate investigation. WSDA investigators approach each investigation with the knowledge that its findings may be pertinent to litigation. The most WSDA can do for a grape grower not performing the required leaf indexing is simply documenting the allegation(s) of a complaint without investigating any of its elements. Remember, “It is a violation of WSDA rule to provide false or fraudulent information.”

Please familiarize yourself with the training and reporting information provided at the WSU-FEQL website ( If you require further assistance contact a WSDA-PMD representative.

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