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X-disease Phytoplasma & Little Cherry Virus Scouting & Sampling

It is critical to scout and sample for X-disease phytoplasma and Little cherry virus-1, 2 this year in order to stop the spread of the epidemic.

Download scouting fliers here

Little Cherry Scouting flier OSU WSU vf (2020.05.20)

Muestreo de X Fitoplasma y Little Cherry Virus flier WSU OSU vf (2020.05.20)

For 25 pg scouting guide

X-disease Phytoplasma and Little Cherry Virus Scouting and Sampling Guide


scouting and sampling flow chart

What to samplewhat to sample

Submit four five-inch cuttings from the diseased limb(s) including leaves, and FRUIT STEMS.

Where to sample

Trees with symptoms: Sample from symptomatic limbs.

Trees with no symptoms: Sample from each leader. *Samples only needed in non-confirmed blocks/ adjoining trees. See flow chart.

When to sample

The week before harvest to mid-August.

Sample condition

Keep tissue cool (can use cold pack to keep sample cool, but not in direct contact). Old or dried tissue is more likely to have false negatives.

Where to send samples

Washington Eurofins Cascade Analytical. 1008 W. Ahtanum Rd. Union Gap, WA 98903. (509) 452-7707 For drop locations visit

Cascade Analytical is undergoing additional cross-validation with WSU for sample testing. Consider delaying sample submission the week of July 13.

Oregon The Oregon State University Plant Clinic


Example Zirkle scouting on four wheelersTeah Smith and her crew scout in teams. Teams scout with one person on each side of the tree on four-wheelers in low gear   looking at every tree. They flag trees with flagging tape that is labeled numerically and alphabetically (i.e., Sample 22 is positive so the 8 trees around it are labeled as 22A, 22B, 22C ). They remove positive trees and sample from adjoining trees. If adjoining trees are positive, they are removed, and the next tree out sampled until trees are all negative. They remove trees by pulling trees out so that as many roots as possible are removed. In general if more than 20-30% percentage of the block is infected or has been removed due to X Phytoplasma the entire block is removed.

Example GS Long Garrett Bishop and his group focus on spots identified by cutting samplegrowers or fieldmen and then randomly scout at least 25% of entire block. Using quads in low gear (about 3 miles per hour) they look at the whole tree when scouting and     sampling, especially concentrating on both small limbs off the main scaffold and the lower section of the tree that often seem to be symptomatic. The growers GS Long scout for remove trees using either the cut stump or notch (drill) herbicide method.

Example Goldy Dale Goldy’s scouts walk the block in the week before harvest. They find there are too many false negatives when scouting is done earlier. They look at every tree. “We want to find new  outbreaks so we have to look at every tree.” They remove symptomatic/  positive trees by first drilling and applying herbicide in holes and then cutting out dead trees. They find that timing for herbicide application is important. Trees treated in Aug die quickly. If more than 20% is affected they remove the entire block.

Example Stemilt Hannah Walter’s group works in teams with a lead scout.Stemilt tagging system Scouts GPS tag and flag symptomatic trees. They send in a portion of symptomatic trees for laboratory confirmation to check accuracy for new scouts. For example, if they flag 20 trees, they send in samples for 10. If all 10 come back positive they remove all 20 flagged trees. For removal they use either the herbicide painted cut stump or “notch” drill and inject  herbicide  method. Walters says “We are finding X scattered randomly in blocks vs hot spots so it is important to look at all trees in a block.” They consider age of trees and economics of block when deciding whether to remove a whole block.

For more information

X-Disease Phytoplasma (Western X)

X-Disease and Little Cherry Virus Scouting and Sampling Guide

Little Cherry Virus”

Another Bad Year for Little Cherry Disease

Western X Questions and Answers: What do we know? What do we not know?

BMPs for tree removal for X disease and Little Cherry Virus infected trees

Little Cherry Disease Eligible for Tree Assistance Program

LCD Task Force Rolls Out New Online Form to Streamline Testing

Cherry Prunus spp. X-Disease


Tianna Dupont, WSU Extension (509) 293-8758

Bernardita Sallato, WSU Extension (509) 439-8542

Ashley Thomson, OSU Extension (541) 296-5494

Karen Lewis, WSU Extension (509) 760-2263 articles may only be republished with prior author permission © Washington State University. Republished articles with permission must include: “Originally published by Washington State Tree Fruit Extension at” along with author(s) name, and a link to the original article.



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