It is important to clean up two-spotted mite infestations prior to fall to minimize infestations next spring.
Two-spotted spider mites (TSSM) multiply quickly during the hot, dry days of summer and are common on greenhouse tomatoes, herbaceous perennials, weeds and many other hosts. It takes about 28 days to develop from egg to adult at cool temperatures (50-68°F) but only about 8 days at 77-95°F.
Production areas with black fiber cloth were hot, hot, hot this week. Garden mums, flowering cabbage and kale may exhibit signs of wilting during extended periods of 90 plus degree temperatures. The solution may not be as easy as turning on the irrigation. Plants wilt when the soil is dry, but wilting will also occur in hot weather which may cause plants to be stressed, or if the roots are damage from a root disease such as Pythium, even if the soil is saturated with water. When the roots stop functioning the plants will show signs of stress by wilting.
The caterpillar of the sunflower moth, Homoeosoma electellum, damages the flower heads of echinacea, sunflower, marigolds cosmos, coreopsis and other composites (Asteraceae). 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.
Wet, rainy conditions are bringing out the slugs. Slugs feed actively at night, and injure plants by chewing ragged holes in leaves or stems. Feeding damage caused by slugs may be confused with damage caused by caterpillars, however caterpillars leave fecal droppings. Slugs leave shiny trails of dried slime. The slime helps protect their bodies from desiccation. After mating, adults lay round, clear eggs in clusters in damp locations. Slugs mature over several months to a year. Slug baits although messy, are probably the most effective tool for management.
Now that you are scouting your outdoor herbaceous perennials, it is important to keep an eye out for native beneficial insects and mites. If they are present in sufficient numbers, they can do your work for you! These good guys may be either generalist predators that feed on many pests during their lifetime or more specialized host specific parasitic wasps that may parasitize aphids.