July 25, 1997
A hickory sample showing signs of downy leaf spot was recently submitted to the Plant Disease Clinic. The sample was collected in Dubuque county. Downy leaf spot, also referred to as white mold or white leaf spot, is caused by the fungus Microstroma juglandis. Downy leaf spot affects various species of walnut and hickory.
A hot, dry summer like has been occurring in many parts of Iowa could mean spider mite problems for many of our landscape and garden plants. Spider mites feed externally on the foliage of nearly all vegetables, flowers, trees and shrubs. They use piercing-sucking mouthparts to puncture the plant tissue and feed on the liquid within the cells. In light infestations the foliage will appear to be speckled with very tiny yellowish-green spots. If the population of mites increases the damage can become severe enough to turn the foliage entirely greenish-yellow and eventually tan or brown.