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Nursery & Forest

Degree Days

Nursery & Forest
Volume 58 Number 6 Date 06/06/2013

ANTHRACNOSE - Sycamores and viburnums at nurseries in Washington and Jefferson counties are exhibiting foliage with brown, necrotic spots caused by the fungal disease Anthracnose. This disorder rarely results in permanent damage to trees unless severe symptoms persist for several consecutive years. Raking fallen leaves and pruning branches to promote air flow are the recommended cultural controls.

COLUMBINE LEAFMINER - Leaf mines caused by the larval stages of this insect were noted this week on columbine in a Waukesha County garden center. The serpentine mines initially appear whitish in color and eventually turn tan or brown later in the season. Removing and destroying infested leaves will reduce this aesthetic problem.

COLUMBINE SAWFLY - Another columbine pest, the columbine sawfly, was also observed during recent garden center inspections. The green larvae with dark heads were found on columbine 'Clementine Dark Purple' in Jefferson County. Their characteristic pattern of feeding begins at the leaf edges and progresses inward until all leaf tissue except the midveins has been consumed. This spring pest is present from mid-May through early June. Removing the larvae and infested leaves by hand is the preferred form of control, but insecticidal soaps are also effective. Columbine plants usually recover from the feeding injury.

NON-VIABLE NURSERY STOCK - Most nursery plants that have not leafed out by now are considered non-viable and cannot be sold. Dry bulbs and trees and shrubs with plastic-wrapped roots are especially prone to moisture deficiency problems after distribution to retail stores and should be sold within three weeks of arrival. Non-viable stock may be set aside and observed for later growth, but otherwise must be destroyed or returned to the supplier.

-- Liz Meils, DATCP Nursery Inspector