Grapevine virus diseases

A picture of a grape leaf sample taken from a single vine.
Example of a grape leaf sample taken from a single vine. Four leaves with petioles in a labeled, resealable plastic bag.

How to collect, handle and submit the ideal grape sample for virus testing

Grapevines are known to host more than 80 different species of viral pathogens. Co-infection of diverse viruses in a single vine is not uncommon and disease diagnosis based on symptom observation alone is unreliable due to the variability in the expression of symptoms and the occurrence of viral strains that cause asymptomatic infections. If you suspect virus infection in your vineyard, follow our recommendations to properly collect, handle, and submit the ideal grape sample for virus testing.

Sample collection

  1. Select suspect vines. A suspect vine is a vine with atypical growth or performance. For example, vines with discolored leaves (red/purple, yellow), leaf rolling or distortion, stunted shoots, uneven fruit ripening, and so on. We recommend flagging the vines selected for sampling as it may be necessary to re-sample and re-test. 
  2. Label sample bag. Using a black or blue permanent marker, label a gallon-size resealable plastic bag with your sample identifier. For example, "Chardonnay # 1".
  3. Avoid sample cross-contamination. Our testing method is very sensitive, any infected grape sap can compromise the test results of a healthy vine.
    1. Use disposable gloves when taking samples from more than one vine. Remember to always change your gloves before collecting samples from another vine. 
    2. Never touch the end of detached leaves.

Single-vine sampling

Diagram showing single-vine sample collection.
Sample collection from a single grapevine: Collect a total of four leaves, two from each cordon. Make sure one comes from the front and the other from the back of the vine. Image by Caitlyn Byrne.

A sample from a single vine consists of four (4) detached leaves with petioles. These leaves should be of intermediate age (not too young, not too old).

  1. Reach for a leaf and pull it backwards until the petiole snaps off.
  2. Take two (2) leaves from each cordon, making sure one comes from the front and the other from the back of the vine.
  3. Stack leaves on top of each other and place them inside your labeled bag. Insert petioles first.
  4. Push some air out of the bag and seal it. Don’t add extra moisture to the sample.

Multiple-vine sampling

Diagram showing a composite sample of five grapevines for virus testing.
Sample collection from multiple grapevines. In this example, four leaves from five grapevines are collected to make a composite sample.

A sample of two, three, four or up to five vines may be submitted for testing. This is an alternative sampling strategy to reduce testing costs. A collection of individual samples is called a composite sample

  1. Samples from individual vines are collected following the same procedure described above (read "Single-vine sampling").
  2. Depending on the number of selected vines, a sample bag will contain a total of 8, 12, 16 or 20 leaves.

Handling and shipping samples

Detached leaves can rapidly deteriorate, especially in warm weather. In the field and during transport, always keep samples inside a cooler with ice packs but not in direct contact as freeze damage can occur. We highly recommend submitting samples on the same day of collection; however, samples can be refrigerated for up to 48 hours.

Before shipping your sample:

  1. Make sure the leaves are still crisp and fresh. If the sample is in bad condition, we cannot test it.
  2. Fill out a Sample Submission Form and place it inside a separate plastic bag.

Please avoid shipping samples on Fridays as packages are not delivered to campus on weekends; samples will not arrive to the lab in good condition the following week.

Ship overnight (FedEx preferred) or deliver samples directly to our facility at:

MSU Plant & Pest Diagnostics
Att. Laura Miles
578 Wilson Road, CIPS 107
East Lansing, MI 48824

Grape virus tests

Samples can be tested for the following: 

  • Grapevine leafroll-associated viruses (GLRaV-1, -2, and -3)*
  • Grapevine red blotch virus (GRBV)
  • Grapevine Pinot gris virus (GPGV)
  • Grapevine fleck virus (GFkV)
  • Arabis mosaic virus (ArMV)**
  • Grapevine fanleaf virus (GFLV)**
  • Tobacco ringspot virus (TRSV)**
  • Tomato ringspot virus (ToRSV)**

Testing fees

Please note that fees for out-of-state samples are doubled.


Fee per sample

Single virus test


* Leafroll viruses (3)


** Nepoviruses (4)

(Viruses transmitted by nematodes)


All viruses (10)


Support provided by Project GREEENMichigan State Horticultural Society (MSHS), Michigan Grape and Wine Industry CouncilMichigan Wine Collaborative (MWC) and Michigan Department of Agriculture and Rural Development (MDARD).

Contact us for more information!

Phone: 517-355-4536