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Chicago Urban Gardening

The day to day experiences of a University of Illinois Extension Urban Horticulture Educator in Chicago, Illinois

May 26, 2011

Spruce Disorder Found for First Time in Illinois

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," said 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 said. "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 said 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 said 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 said. "A tree can have just one of these needle casts or two or more."

Unfortunately, management recommendations are sparse, she said. Bruce D. Moltzan of the Missouri Department of Conservation indicates that 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/.

Posted by Ron Wolford at 3:32 PM | Permalink |
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May 3, 2011

Six Spring Rose Pruning Pointers

Spring is an annual process of renewal for gardeners and for roses. Don't be afraid to prune your roses. Roses are tough plants and will even survive your pruning mistakes. The main goal in rose pruning in the spring is to open up the center of the plant to increase light and air circulation. The following are a few tips to guide your pruning.

  1. Purchase some good thorn-resistant gloves. Use sharp bypass pruners. Bypass pruners will cut stems up to 3/4 of an inch thick. Avoid anvil type pruners because they tend to crush the stem. Consider using long-handled loppers and a pruning saw for thicker stems.
  2. Spring is a prime time for pruning roses. The flowering of forsythias is a signal from Mother Nature that it is time to prune roses.
  3. General pruning tasks: Remove any dead or diseased wood, remove "twiggy" growth from the center of the plant or branches that rub each other, remove weak or thin stems, cut back above a bud at a 45 to 60 degree angle that faces the outside of the plant. This will promote new growth out from the center of the rose bush. Prune to shape the plant.
  4. Pruning hybrid teas, grandifloras and floribundas: These types of roses flower on the current season's wood, so it is important to cut out all dead and small canes. Try to leave 3-5 healthy canes spaced evenly on the plant. Cut the healthy canes back leaving at least 3-5 outward facing buds on each cane.
  5. Pruning climbers and ramblers: These types of roses may require little or no pruning for the first two or three years of growth. Prune just to shape the plant and cut out dead canes. Climbing roses should be pruned in early spring and ramblers should be pruned after they flower in early summer. To generate more blooms it is recommended when pruning to cut back the side shoots to 3-6 inches long. In the summer remove all faded blooms.
  6. Pruning shrub roses: Repeat flowering shrub roses may need very little pruning the first season. More extensive pruning will be needed as they get older. Prune to maintain the shape. After two to three years, prune using the "one-third method. Cut out one third of the oldest canes in the spring. Pick out one third of the youngest, healthy canes that grew the previous growing season to keep and remove all other canes.

Posted by Ron Wolford at 9:17 AM | Permalink |
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