CAHNRS - Department of Entomology

Food & Environmental Quality Lab

Leaf Index and Severity Rating

Dear Grape Grower:

The Washington State University-Food and Environmental Quality Lab (FEQL) and Washington State Department of Agriculture (WSDA) request a limited amount of your time to provide the best possible information for investigating vineyard injury from phenoxy herbicide exposure. A full explanation of the project is provided below.

The most important detail will be logging the date a leaf unfurls. It is important that you make these observations a minimum of once per week since there can be a delay from the time of phenoxy herbicide exposure to the appearance of symptoms. Be committed before the season starts. You cannot go back and guess or back date when a leaf unfurled. If severe symptoms are observed, do not hesitate to immediately contact WSDA.

The person recording leaf index information should be on-site at the vineyard most of the time. Employee observations are very important for recording weather and spraying activities at and near your vineyard. Please do not assign this responsibility to somebody off the farm.

An example of a completed Leaf Index form is available from this site. The Washington State Department of Agriculture (WSDA) will also provide on-site or over-the-phone technical assistance to explain any questions that you may have for conducting this leaf indexing process.

For leaf indexing technical assistance contact
Gail Amos, WSDA 509-249-6930 or email
Vince Hebert, WSU-FEQL 509-372-7393 or email


The off-target movement of cereal grain broadleaf herbicides to grape vineyards has affected grape production in the Pacific Northwest over the past 30 years. Although sound management practices have been implemented to reduce chemical drift, vineyard injury still remains a concern. Continued grower involvement in monitoring plant symptomology from phenoxy-type herbicide exposure (i.e., exposure from airborne 2,4-D, dicamba, MCPA) will be key to identifying the impact of herbicide drift on grape production.

Leaf indexing must accompany any herbicide-exposure complaint to the Washington State Department of Agriculture (WSDA). Leaf indexing is a simple process and can provide valuable information on symptoms of herbicide injury. This Website provides a leaf-index guideline for dating exposure, which is critical to an herbicide injury investigation. Leaf-position dating is important because of the lag time between the exposure and the appearance of symptoms. Leaf indexing must be performed weekly by the vineyard operator/assistant from bud-break through full bloom or through vine hardening.

Leaf Index; and Report of Loss forms are available as links from this page. An example of a completed Leaf Index form is also provided.

Leaf Index

To begin leaf indexing, select some representative shoots for observation. The vines from which shoots are chosen should be mature and typical of the vineyard. The number of shoots selected will depend on your time and ability to observe the shoots on a weekly basis throughout the growing season; a minimum of three is recommended. The variety selected for observation will not be as important as selecting a set of varietal shoots that you will be able to observe weekly throughout the season. The selected shoots are not to be pruned during the observation period.

Note: While phenoxy-type symptoms generally look similar regardless of the variety of grapes, there are certain varieties that can exhibit herbicide-exposure symptoms more readily than others. In most cases, the white varieties will exhibit greater herbicide symptomology than other varieties.

Mark the selected shoots with flagging tape or other physical marker that will be easy to see. This will aid in finding the correct shoot again. Alert the field crew that flagged shoots should not to be pruned. The flagged shoot must be kept upright during the observation period.

Flagging a shoot

Figure 1

Do not flag the actual shoot you will be observing. Attach flagging material to main stem near shoot. It is also a good idea to flag the end of the row so you can quickly find the flagged vine.

Make Vine Observations

Weekly observations and accurate documentation of when leaves unfurl provide the most important information for an herbicide-injury investigation. Regularly record on the Leaf Index form or in your observational notebook the date and the number of leaves expanded on your selected shoots. Include leaf appearance and any other observations that may be important for documentation as well as for your own learning experience. The WSDA Leaf Index should accompany your notebook entries.

Leaf development

Figure 2

A leaf is considered expanded when the leaf unfurls.

Designate the first leaf that opens (basal) with a "1," the next leaf with a "2," and so on. Record this information in your notebook. Leaves may be marked with a "bullet-point" Sharpie marker after the cutin has formed for easy reference on follow-up observations.

Number each leaf

Figure 3

Write the leaf number directly on the leaf.

  • Select shoots and make observations on a weekly basis from April-July
  • Use flagging tape to mark indexed shoots
  • Label leaves with permanent marker after cutin formation
  • Record date and weekly observations in a notebook/logbook and/or WSDA report forms (Leaf Index) (Report of Loss)
  • Keep observation shoots in upright position

Document Vine Development with Photos

Photographing your flagged vines is not required but can be useful to ensure complete documentation. A digital camera is ideal for this because you can immediately determine if the photo is clear and accurate, and you can readily download the photo to a computer for archiving. Additionally, a photo can be electronically sent to WSDA for evaluation when questions arise.

Get a clear photo of each mature leaf. You may take useful photos up to a week after the date the leaf expands. When photographing the leaves, use a backdrop such as a board with a dark piece of cloth covering it so the leaf will be more visible in the photo. Also, ensure the date is somewhere in the photo. This can be easily accomplished by printing the date on a colored address label or colored label tape on the backdrop. White labels can cause a glare in the photo making the date unreadable.

Date each photo

Figure 4

Be sure the date the photo is taken appears somewhere in the photo.

We suggest downloading and labeling the pictures as soon as possible after the observation and placing the pictures in chronological order. Below each leaf picture, include the leaf number and any observations you have made. By doing this, you have a visual history of each leaf on a selected shoot. This documented visual reference will aid in a proper investigation.

Assess Phenoxy-type Herbicide Symptoms

Exposure to a phenoxy-type herbicide before cutin formation will cause a leaf to show herbicide-exposure symptoms. The leaf will not grow out of these symptoms. These symptoms can range from mild to severe as illustrated below.

Normal leaf

Figure 5

Normal leaf

Abnormal leaf margins

Figure 6

Abnormal leaf margins
The leaf margin is the outer edge of the leaf.

Reduced or lack of sinus

Figure 7

Reduced or lack of sinus
Sinuses are the large indentations of the margin normal in a grape leaf.

Vein clearing

Figure 8

Vein clearing
The color is gone from the veins in the leaf.

Severe veination

Figure 9

Parallel veination
The veins are nearly parallel to each other from base to tip of leaf

Rate Leaf Symptoms

Individual leaves can be rated using the Severity Rating. The rating ranges from 0 to 5 with 0="no observable phenoxy-type symptoms" and 5="severe phenoxy-type symptoms." Use the photos and documented field descriptions to aid in rating symptoms.

Severity Rating
Normal leaf


No visible symptoms of phenoxy-like herbicide exposure. Margins and lobes are well defined. No apparent rugose texture.

Click for larger image


Possible rugose (bumpy) features on leaf surface. Slight shortening of lobes and sinus. The leaf will grow to normal or near normal size.



Rugose features as well as disfigured margins. The leaf will be noticeably, but not significantly, smaller than leaves with a lesser rating.



Deformation of leaf margins. Has diminished or possible lack of sinus. Lobes may be blunt. Lighter leaf color. Leaf will be significantly smaller than those with a lesser rating.



A definite deformation of leaf margins and sinus. Noticeable vein clearing. The leaf will be very stunted in size.

Severe veination


The leaf will be severely dwarfed. Veination will be parallel. The margins may resemble the end of a straw broom. Grossly deformed leaf.

Forms & additional information

Use of Synthetic Growth Regulator Herbicides;  A Continuing Concern with Wine and Juice Grape Vineyards in Washington  State Agriculture

WSDA –WSU Leaf Index Management Tool

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Food & Environmental Quality Lab, 2710 Crimson Way, Washington State University - Tricities, Richland WA 99354, 509-372-7464, Contact Us