The arrival of cool temperatures reminds us that it won't be long before perennials will need covering for winter protection. Overwintering perennials for the first time? The process for successful overwintering begins with healthy plants.
Cool night temperatures, warm day temperatures and heavy dew are favorable for many foliar diseases including Bacterial leaf spot, caused by Pseudomonas cichorii on garden mums. Symptoms appear as black spots on foliage concentrated at the base of the plant. The spots often begin at the leaf margin but may also occur randomly. The spots are soft when tissue is wet and sunken and brittle when leaves dry. From the leaf, the bacterium can move through the petiole and into the stem resulting in a canker.
Monitor root health and test growing media of garden mums. Take random samples of plants out of their pots and examine roots carefully. The roots tell a lot about overall plant’s health, often before the top growth shows symptoms. Signs of poor root health are blackened or rotted roots or the lack of roots, especially young feeder roots. Diseased roots will not take up fertilizer.
The familiar imported cabbage worms adults can be seen fluttering above ornamental cabbage and kale. The adult is a white butterfly tinged with yellow on the underside of its wings.
The caterpillar of the sunflower moth, Homoeosoma electellum, damages the flowers of echinacea and sunflower. Newly hatched larvae are pale yellow, but darken to shades of brown or purple with longitudinal white stripes. Look for mats of webbing on the face of flowers for signs of larval feeding. The injury caused by larval feeding can lead to Rhizopus head rot.