2004 Season Review: Ornamental Plant Diseases

Paul Pecknold, Professor, Botany & Plant Pathology, Purdue University

Shade tree anthracnose was light to moderate this past growing season.  Maple anthracnose was almost nonexistent, while ash, oak and sycamore anthracnose were light to moderate.  The degree of disease severity and occurrence varied throughout the state depending on the amount and duration of early spring rainfall and the stage of plant growth.  As usual, apple scab was very evident during the spring period, but did not reach the epidemic levels that it has in past years.  Other prominent leaf diseases included Guignardia leaf blotch of horse chestnut and buckeye; powdery mildew of lilac and susceptible shade trees, and cedar apple rust.  Of interest was the lack of blister leaf of oak, juniper tip blight, and cedar quince rust, three diseases that have been fairly prominent in previous years.  Sphaeropsis tip blight continues to devastate pine plantings throughout the state; especially Austrian and Scotch pines.  Also of concern was the apparent increase in oak wilt reported from northwest Indiana.  Overall, the past growing season experienced moderate disease pressure resulting in an ‘average’ year for landscape tree and shrub diseases.