LANSING, Mich. — Two exotic blueberry plant diseases have been identified in Michigan for the first time — blueberry shock and blueberry scorch.
Both viral plant diseases have the potential to cause significant losses to blueberry producers; however, they are not a threat to food safety or human health.
Department and Michigan State University officials are aggressively implementing a response plan to eradicate these diseases.
Top producer
Michigan is the nation’s number one blueberry producer with more than 19,000 reported acres producing 110 million pounds of blueberries, valued at $124 million last year.
The department’s pesticide and plant pest management division has been watching for these diseases due to their presence in certain West Coast and Mid-Atlantic states. The division has also been taking steps to prevent the diseases from entering the state through issuance of an external quarantine in 2002 and through routine sampling.
“Although not totally unexpected, we are very disappointed these two serious diseases have been identified in southwest Michigan — the state’s blueberry belt,” said Michigan Department of Agriculture Director Don Koivisto.
Annemiek Schilder, associate professor of plant pathology, was part of the team that identified blueberry shock in a research plot at Michigan State University’s Trevor Nichols Research Station in Fennville.
“Blueberry shock symptoms may look similar to spring frost injury or common plant diseases such as phomopsis twig blight, but rapid testing confirmed our suspicions,” Schilder said.
Blueberry scorch virus was discovered at a private farm in west Michigan. The infected plants have been destroyed, and department agents are testing adjacent areas to verify blueberry scorch disease has not spread.
Blueberry shock-infected plants suffer from loss of foliage and blossoms resulting in yield loss the first year of infection.
Fruit production may resume, but researchers believe this disease could be more severe in Michigan’s northern climate than in its native region, the Pacific Northwest.
Symptoms
The infected plant serves as a source of infection to other nearby plants since blueberry shock is transmitted by pollinating insects. Blueberry scorch disease symptoms are similar to shock symptoms.
In the spring, shoot tips will die back, sometimes on just a few branches. The flowers may blight just as the earliest blossoms open. Scorch-infected plants repeat this symptom cycle each spring until the entire bush becomes infected, typically within three years.
Fruit production and shoot growth are seriously reduced on scorch-infected plants. Scorch is transmitted from plant to plant by aphids. There are no known cures for either of these plant diseases.
Schilder said researchers believe both diseases are restricted to small areas. However, buying plants from a nursery selling virus-tested plants is the best way to prevent further infection. She said both plant diseases can be spread through infected cuttings.
For more information, visit the Michigan State University’s blueberry Web site at www.blueberries.msu.edu or contact Schilder at 517-355-7539.
