Sudden Needle Drop (SNEED) caused by Setomelanomma holmii has been discovered for the first time in Illinois. The University of Illinois Plant Clinic has diagnosed spruce samples from both central and northeastern Illinois.
"While SNEED has been found in several surrounding states, this is a first find in Illinois," says Suzanne Bissonnette, director of the U of I Plant Clinic. "We are pursuing independent identification since this is a first find as well as proceeding with qPCR analysis for verification."
SNEED has been found on Norway, white and Colorado blue spruce trees. Symptoms of SNEED are yellowing and eventual browning of older needles, Bissonnette said. Typically, by the end of summer, all of the needles on affected branches fall off except the newest needles on the tips of the branches.
Symptoms noticeable now are nearly defoliated branches that may still have a few brown or half brown needles attached or no old needles and just new bud growth. Branches affected by needle drop may be scattered throughout the tree or the entire tree may be affected.
"Unlike our other common fungal needle cast diseases, the fungus doesn't produce fruiting structures on the needles," she says. "While spruce needles don't show signs of fungal infection, the twigs will have numerous small black fruiting structures or pseudothecia. Then another type of fruiting structure called a pycnidia produces small clear spores called micro-conidia. We have found both pseudothecia and the probable micro-conidia on our samples in May."
Although the fungus is found infecting symptomatic trees, Bissonnette says there is still a question whether it is a pathogen. It may be a pathogen or simply a fungus taking advantage of a tree stressed by drought, heat, poor planting or other environmental factors. Researchers at the University of Wisconsin are pursuing pathogenicity tests with the fungus to verify or negate it as a pathogen.
To help with field diagnosis for sampling, she says that SNEED fruiting structures will not be on the affected needles.
"If you do see fruiting structures on the needles of a symptomatic spruce, you are most likely looking at either Stigmina (http://hyg.ipm.illinois.edu/article.php?id=31) or Rhizosphaera (http://hyg.ipm.illinois.edu/article.php?id=13) or another fungal needle cast," she adds. "A tree can have just one of these needle casts or two or more."
Unfortunately, management recommendations are sparse. Bruce D. Moltzan of the Missouri Department of Conservation indicates fungicides for control of Rhizosphaera needle cast can provide control in nurseries and smaller landscape trees.
For more information, read the May 27 edition of the Home, Yard and Garden Pest newsletter online at http://hyg.ipm.illinois.edu.