July 12, 2006

Angular Leaf Spot of Cucurbits

We recently received a pumpkin sample showing marginal chlorosis (yellowing) of the leaves. The combination of symptoms and the presence of the bacteria in the sample were indicative of a bacterial disease. Angular leaf spot is a common bacterial disease of pumpkins and other cucurbits that causes chlorosis and necrosis (death) of leaf tissue.

Plant Disease Clinic Update - July 12, 2006

Samples with the following problems have been seen in the Plant Disease Clinic recently:

Angular leaf spot on pumpkin

Anthracnose on oak and maple

Ash flower gall

Bitter Cucumbers

Bitterness in cucumbers is caused by the compounds cucurbitacin B and cucurbitacin C. The cucurbitacins are normally found in the leaves, stems and roots of the cucumber plant. The cucurbitacins spread from the vegetative parts of the plant into the cucumber fruit when the plants are under stress. Hot, dry conditions are usually responsible for bitterness in cucumbers in Iowa.

Shrubs for Shady Sites

When selecting shrubs for the home landscape, gardeners should carefully examine growing conditions at the planting site. Most shrubs perform best when grown in areas that receive partial to full sun. However, there are shrubs that can be successfully grown in partial shade. (Sites in partial shade receive 2 to 4 hours of direct light.) A list of deciduous shrubs that can be grown in partial shade is provided below.