Byron, a Welling-area producer, called me last May, concerned about the yellow patches he’d found in his barley field. “I’m unsure what’s causing it. Given the spring we’ve had, it could be caused by frost or excess water, chemical damage or leaf disease,” said Byron. He asked me to pay a visit to his operation to help solve the mystery.
At the field, I noticed the yellow patches occurred mainly on the outer edge of the field, and there was some major stunting of the plants in these areas. We were able to rule out fertility, frost damage and water stress early in the day. And as soon as I saw some tiny, yellowish, wedge-shaped insects — not even half a centimetre in length — hopping around on the leaves of some of the damaged plants, I knew I’d found the cause of the trouble in Byron’s field leafhoppers!
Leafhoppers can be carriers of aster yellows phytoplasma. The phytoplasma is transmitted to the leafhopper when it feeds on plant sap. The sap-sucking insects then transmit the phytoplasma from plant to plant, causing aster yellows disease. Not all leafhoppers carry the specialized bacteria (phytoplasma), but once a leafhopper is infected, it can pass on the disease for as long as it lives.
In the spring, migrating leafhoppers from the United States can carry the phytoplasma north. The pathogen can also overwinter locally in perennial crops and weeds. Aster yellows affects barley and other crops, such as canola, by stunting plant growth and causing chlorosis.
After discussing the case with a research scientist from Alberta Agriculture and Rural Development, we found that there was no economical threshold to spray for leafhoppers. As there was nothing that could be done at this time, the crop recovered as best it could on its own, but yield in these damaged areas was significantly affected.
In the future, Byron may want to look at spraying for leafhoppers as a possible solution. Unfortunately, severity of this disease ranges from year to year depending on the size of the leafhopper population, environmental conditions and the number of infected leafhoppers.
In general, it’s a good idea to continuously scout fields early and often in order to determine the cause of crop damage and utilize all resources possible to prevent further issues. †