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Progress Towards Leafhopper Degree-Day Model Slow but Steady

Written by Dr. Katlyn Catron, Postdoctoral Researcher, WSU TFREC Wenatchee. July 11, 2022


Image with yellow background and a leafhopper in the middle of it.
A Colladonus reductus adult – one of the primary vectors of X-disease in cherries – on a sticky card used for population monitoring. Photo by Katlyn Catron

Researchers at the WSU Tree Fruit Research and Extension Commission are making slow but steady progress on a tool that would make management of X-disease spreading leafhoppers more precise and less expensive for cherry growers. This growing season is the first in a multi-year project tracking leafhopper development against temperatures to develop a degree day model for Colladonus reductus, the primary vector of X-disease. If successful, growers will be able to use temperature data from their location to time sprays for the most vulnerable stages of leafhopper growth. With better chemical control of the leafhopper vectors, growers might finally have a fighting chance against X-disease.

Degree-day models, which have been successfully used in other tree fruit systems like apples and pears, use temperature (more specifically, heat units accumulated across a season) to predict population spikes and crashes in insect pests. To build a model, populations of the target pest should be tracked over several growing seasons and various locations with differing temperature regimes. Then, that data is refined and mathematically shaped into a predictive tool. Typically, the more data collected, the better the model is at predicting future pest populations, so sampling over multiple seasons in a variety of locations is critical. WSU is currently tracking leafhopper populations at ten sites throughout the Columbia River Valley cherry growing regions using multiple sampling methods.

Female researcher holding a vacuum to collect leafhoppers from the ground in a cherry orchard
Researcher Katlyn Catron uses a modified leaf blower/vac to sample for leafhoppers in an organic cherry orchard. Photo by Garrett Bishop

In addition to building the degree-day model, TFREC researchers are also testing a variety of chemical insecticides against the pests to find the most effective chemistries. This is a continuation of several years of chemical tests on wild-caught leafhoppers, but more active ingredients and application methods are being included every year. This growing season, organic and conventional products will be tested as direct sprays, aged residues, and, potentially, soil drenches. Additionally, particle films are being tested for leafhopper repellency. Results from previous years’ research and insecticide recommendations can be found in the 2022 Crop Protection Guide for Tree Fruits in Washington, available online at


Funding and acknowledgments

Funding was provided in part by the Washington Tree Fruit Research Council and industry cooperators. This work would not be possible without our grower cooperators.

Additional Information


Resources for Little Cherry & X-disease management 2022



Katlyn Caron, Ph.D.
Postdoctoral researcher, WSU TFREC Wenatchee






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