Diseases and Pests

by Heather Prince

First found in Illinois in 2015, jumping worms, an invasive species of earthworm, has been confirmed in 25 counties across the state, and observations suggest eggs can overwinter in warmer areas of Illinois. Native to East Asia, they have been sold as bait for fishermen. Adult jumping worms are about four to eight inches long. The body is dark gray or brown, with a milky white or light gray band of tissue (the clitellum). The clitellum is smooth, opposed to raised as in other worm species. When disturbed, jumping worms wriggle and thrash vigorously. These Asian worms are cause for concern as they are voracious eaters of organic matter to the point their castings give the top layers of soil a grainy consistency like dry coffee grounds. Their activity changes soil structure and can affect plant growth.

Jumping worms can be found in the top three to four inches of soil and in layers of mulch or leaves. The goal is to prevent the further spread of these invasive worms and their eggs. Clean equipment between sites, do not carry mulch or soil from known affected properties to other sites, and do not share divisions of plants from yards with suspected infestations. If soil is infested, fertilization and mulching may help reduce the adverse effects of the worms.

Dutch elm disease (DED) is still out and about on elm trees. June is a good time to scout elm trees for yellowing leaves in the canopy. Often a single branch will turn yellow seemingly overnight before spreading to neighboring branches. Positive identification requires laboratory culturing. Contact the University of Illinois Plant Clinic before you send the sample for current Elm streaking fees (usually reasonable) and plan on about a week of lab time. Preparing a Sample:

One of the typical ID characteristics of DED is vascular discoloration or streaking of the sapwood. Peel back the bark of a symptomatic branch to check for brown streaks in the otherwise tan outer sapwood. Verticillium wilt and dothiorella wilt can also cause this streaking in elm but are not as prevalent. Each of these fungi has distinct structures that can be identified in laboratory cultures. Cut several eight- to ten-inch-long sections from wilting, but living, branches that show definite streaking in the sapwood. The fresh wood sections should be about finger thickness and can be sent in plastic or foil to the Plant Clinic for testing. Chilling the wood should not be necessary with Dutch elm suspected samples.

University of Illinois Extension Service https://web.extension.illinois.edu/state/ horticulture/index.php 217-333-0519 The Morton Arboretum http://www.mortonarb.org/Plant Clinic: http://www.mortonarb.org/trees-plants/ tree-and-plant-advice/ 630-719-2424 Chicago Botanic Garden Plant Information Service: https://www.chicagobotanic.org/ plantinfoservice 847-835-0972