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Round and About

May 31, 2000

Because the Plant Clinic staff are frequently asked what diseases are occurring in ornamental plantings in the state, we are listing here a few of the hot items for the last 2 weeks. Sycamore anthracnose has not let us down this year. Despite a slow start when we had warm, dry conditions, this disease has the sycamores currently shedding blighted leaves in central and northern parts of the state. They will produce new leaves in this warm weather that will be free of disease, and the tree will recover. Apple scab too has been prevalent in these areas and will soon be causing a similar defoliation of the susceptible crabapple trees. Unfortunately the crabapples will not form enough leaves to replace those lost. They will stay nearly bare all summer. Peach leaf curl has been common for the third year in a row, so read the article in this issue relating to peach leaf curl. If this has been a problem on your peach trees, mark your calendar for treatment next fall. Scotch and Austrian pines now show Sphaeropsis blight problems, mostly from past years. With all the fungal inoculum for this disease present in the landscape, it is sure to be a perennial problem for the next decade. Confirmed cases of Oak wilt (western Illinois) and Dutch elm disease (north and central Illinois) have already passed through the clinic this year. It is not too early to sample suspect trees. Rhizosphaera needle cast continues to plague spruces throughout the state. Although we have not seen it yet, the hot days, cool nights and wet conditions of late should be prompting some Pachysandra blight (Volutella), Botrytis on annuals and perennials, and leaf blights on ivy and other ground covers.

Author: Nancy Pataky


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