Weekly Plant Disease Update
By Brian Hudelson, UW Plant Disease Diagnostics Clinic Director
Website: pddc.wisc.edu
Brian Hudelson focused on fruit crop diseases, particularly in apples, crabapples, and stone fruits:
- Apple scab is active, though symptoms are subtle—yellowing leaves without obvious lesions. Tape mounts reveal heavy sporulation.
- Gymnosporangium rusts (e.g., cedar-apple, cedar-quince rust) are appearing on apples, crabapples, hawthorn, and Amelanchier. Lesions are small now but will enlarge and sporulate on leaf undersides. Infections on Amelanchier have been fruit infections characterized by spiny, powdery fruit.
- Peach leaf curl continues to generate inquiries to the PDDC—even from Nova Scotia!
- Fire blight was confirmed on crabapple and apple. One sample had sticky bacterial ooze and tested positive with a dipstick assay. Entry likely occurred through storm-related injuries.
- Cankers: Brian identified Nectria (asexual stage Tubercularia), Fusarium, and Cytospora on apple branches. The Fusarium sample showed bright orange sporulation.
- A leaf smut on Virginia wild rye was diagnosed. However, the case is likely not serious and may resolve itself with improved fertility.
- Dutch elm disease and oak wilt were confirmed this week.
Additional Plant Disease Resources
- Apple Scab – UW Plant Disease Factsheet
- Cytospora Canker – UW Plant Disease Factsheet
- Dutch Elm Disease – UW Plant Disease Factsheet
- Fire Blight – UW Plant Disease Factsheet
- Gymnosporangium Rusts – UW Plant Disease Factsheet
- Oak Wilt – UW Plant Disease Factsheet
- Peach Leaf Curl – UW Plant Disease Factsheet
Weekly Insect Pest Summary
By PJ Liesch, UW Insect Diagnostic Lab Director
Website: insectlab.russell.wisc.edu
PJ Liesch reported another busy week at the Insect Diagnostic Lab:
- Indoor pests: Mealworms, pantry moths, and carpet beetles continue to show up in homes. One case involved mealworms falling from a ceiling—possibly feeding on unusual substrates.
- Sawflies remain active, especially rose slug sawfly, which has caused near-total defoliation in some cases.
- Scarab beetles are emerging:
- Japanese beetles are not yet confirmed but expected imminently.
- Sand chafers and rose chafers have been reported. Both are associated with sandy soils and feed on similar hosts as Japanese beetles.
- Fall webworm caterpillars are hatching earlier than usual.
- Vegetable pests: Reports of chewing damage on peppers and cabbage with no visible culprits. PJ recommends scouting after dark for slugs, earwigs, or nocturnal caterpillars.
- Brown marmorated stink bug nymphs have been confirmed in Dane County, so egg hatch is underway.
- Beneficial insects: Predatory stink bugs and gall midges are active.
- Milkweed insects: Aphids, swamp milkweed beetles, and longhorn beetles are being reported.
