Insects and diseases showing up on cut flowers

Outdoor cut flower growers in Maryland are seeing grasshopper chewing damage on foliage. Members of Univ. of Md. Extension report grasshopper adults and nymphs are active at this time of year on outdoor crops. They suggest that growers leave an uncut barrier strip of grass to concentrate grasshopper populations. These barrier strips can be treated with conventional or biological controls to reduce grasshopper numbers.

Cosmopepla lintneriana (twice stabbed stink bug) is commonly found feeding on cut crops of cleome and snapdragon, but they have a wide plant host range. Aborted flower buds and distorted growth are common damage symptoms.

Bacterial leaf spot was identified on outdoor zinnia crops earlier this season during periods of wet weather. Disease symptoms have been less common after an extended period of drier weather. Univ. of Md. researchers are evaluating two low toxicity materials for control of leaf spot and powdery mildew. Initial results have shown the products don’t cause any phytotoxic effects when treatments are made during periods of high temperatures.