Michigan State University plant pathologists want to find out what's bugging blueberry plants in the state—or more precisely, what's infecting the plants.
This year, they plan to conduct a survey to determine what virus and virus-like diseases are present, says Annemiek Schilder, a plant pathologist based in East Lansing.
Virus diseases of plants are systemic, and once plants are infected, they cannot be cured. Virus symptoms include plant stunting, leaf and flower malformation, reduced yield, progressive decline and even plant death.
Viruses spread via a range of mechanisms, including insect and nematode vectors, cuttings, etc. The main control method is prevention, especially via the use of clean planting material. Virus-free certification programs are credited with lowering the incidence of virus diseases in blueberry fields nationwide.
"It is especially important that we keep new viruses like blueberry scorch virus out of our production region," Schilder writes in a recent newsletter.
Symptoms of virus diseases are not uncommon in Michigan blueberry fields. Mostly, these are of known viruses, such as blueberry shoestring virus and tomato ringspot virus.
But sometimes other symptoms appear that don’t seem to fit specific descriptions.
Last year, plants with purple blossom symptoms and plant decline were noticed in some blueberry fields in southwest Michigan.
During the summer, leaf scorching, defoliation and plant decline were seen in other locations.
No viruses other than the ubiquitous blueberry shoestring virus were detected in these samples, which suggest that more sleuthing is necessary.
It is also possible that some of these symptoms are due to new viruses or that they are due to herbicide injury.
Some of the newer herbicides have growth regulator properties, and all the manifestations of injury caused by these herbicides may not yet be known.
"We also plan to evaluate a new DNA detection method for blueberry stunt phytoplasma, which would allow us to have a
fast and sensitive method at hand for confirmation of blueberry stunt disease," Schilder writes. "We will invite blueberry growers to send leaf samples of blueberry bushes with suspicious virus-like symptoms. Testing will be free.
"There will be several dates during the growing season when we will conduct large-scale serological testing of blueberry leaf samples."
Advance notice of the dates will be given through the Fruit CAT Alert, Blueberry IPM Update and at grower meetings so that samples can be submitted on or before those dates.
The researchers also will arrange field visits to take plant samples.