By Stephanie Hughes
OSU Ext. master gardener volunteer
A master-gardener friend brought in an unusual specimen for me to examine. It was a rather ugly looking black-eyed Susan.
As I started studying the leaves, I realized I had these same markings on my brown-eyed and black-eyed Susans. In the center of the purple blotches was a green dimple. Underneath was a tiny oval insect nymph with eyes, antennae and little white hairs all around it. I determined it was the rudbeckia psyllid, which can also be found on echinacea.
Many people see the blotches and think disease, but that’s only the feeding of these nymphs. Adults overwinter in cracks of buildings, homes and leaf litter, and emerge in the spring. These adults hold their wings up, resemble miniature cicadas, and have strong jumping legs. They are tiny — just 1/12- to 1/5-inch long, with short antennae. They mate, then lay eggs on young plants.
There are 160 species, as well as many others on crops. The egg hatches into five instar stages. Warm weather brings them out for a few weeks. Cool weather slows them down. Some species have as many as five generations per year, while others only have one. The nymphs are flat and less active, and may secrete waxlike filaments called “lerps.” They secrete “honeydew” that gives way to black sooty mold which you will notice on your black-eyed Susan and coneflower leaves. There also can be waxy masses.
There are native psyllids and invasive ones that can infest citrus, olive, rosewood trees, acacia, eucalyptus, sweet bay, pear, pepper tree, hackberries, boxwood and potatoes. They are responsible for reduced plant growth, distorted plant terminals, discolored galls, and/or die-back. Pear psyllids inject a toxin that blackens or “burns” pear foliage and fruit. Potato and tomato psyllids cause development of yellow, distorted, dwarfed leaves and shoots. Adults introduce bacteria that can cause “zebra chip” disease.
Biological controls include lady beetles, lacewing and predaceous bugs. This is the best option for homeowners. Chemical controls are tricky as they can harm many helpful insects. Pyrethrins, potassium laurate and Neem oil have been successful. Be sure to follow all label directions before using a chemical.