The UW Lab Lens summarizes current pests, diseases, and problems occurring throughout Wisconsin to help you stay ahead of pests in your garden or landscape.
Weekly Plant Disease Update
By Brian Hudelson, UW Plant Disease Diagnostics Clinic Director
Website: pddc.wisc.edu
Brian Hudelson shared a roundup of recent diagnoses:
- Boxwood: Continued winter injury and colonization by Fusarium and Volutella. No boxwood blight confirmed.
- Honeylocust: Large-diameter log sample diagnosed with Thyronectria canker.
- Lilac: Root rot caused by Rhizoctonia.
- Oaks: Leaf diseases including Anthracnose, Tubakia leaf spot, and Monochaetia leaf spot. Bur oak blight confirmed via sporulation of pathogen on petioles.
- Maple: Steganosporium canker—visually distinct from Diplodia or Cytospora cankers which are more common on maple.
- Transplant stress: Conifers planted in summer with burlap and wire baskets left intact—leading to dieback.
- Fruit crops (Apple):
- Frog-eye leaf spot with discrete lesions and minimal sporulation.
- The same fungus also causes a canker disease and a fruit rot (black rot)
- Vinca: Root rot from Rhizoctonia—Brian jokingly called it “biological control.”
- Juniper: Phomopsis tip blight confirmed via distinctive spores.
- Spruce: Rhizosphaera needle cast and shoot blight due to Diplodia.
- Yew: Phyllosticta twig blight; root rot also suspected.
- Vegetables:
- Black rot on cabbage (bacterial).
- Pea root rots from Aphanomyces, Fusarium, Rhizoctonia, Pythium, and Phytophthora.
- Septoria leaf spot on tomato—first confirmed case this season.
- Corn: Bacterial stalk rot linked to irrigation with pond water.
Additional Plant Disease Resources
- Anthracnose – UW Plant Disease Factsheet
- Black Rot – UW Plant Disease Factsheet
- Boxwood Blight – UW Plant Disease Factsheet
- Phomopsis Tip Blight – UW Plant Disease Factsheet
- Rhizosphaera Needle Cast – UW Plant Disease Factsheet
- Root Rots in the Garden – UW Plant Disease Factsheet
- Septoria Leaf Spot – UW Plant Disease Factsheet
- Thyronectria Canker – UW Plant Disease Factsheet
- Tubakia Leaf Spot – UW Plant Disease Factsheet
Weekly Insect Pest Summary
By PJ Liesch, UW Insect Diagnostic Lab Director
Website: insectlab.russell.wisc.edu
PJ Liesch shared a busy week at the Insect Diagnostic Lab, with nearly 100 samples and ID requests. Highlights include:
- Distorted flowers: Coneflower rosette mite and sunflower seed midge caused leafy, green floral abnormalities. PJ emphasized these are not as severe as Aster Yellows and often don’t require plant removal.
- Scarab beetles:
- Japanese beetles: Active statewide, especially near Wausau. PJ is tracking parasitism by the Winsome Fly—reports from Bayfield, Jackson, and Oneida Counties.
- Asiatic garden beetle: Active in Dane and Green Lake Counties; nocturnal and attracted to lights.
- European chafer and masked chafer: Noted along Lake Michigan and in Kenosha.
- Lily leaf beetle: New county record in Winnebago; suspected in Kewaunee.
- Boxwood pests: Damage from psyllid, leaf miner, and spider mite—mostly old damage.
- Lace bugs: Active on hawthorn, crabapple, and asters (e.g., chrysanthemum lace bug).
- Gall-forming insects: Bullet galls on white oaks producing honeydew, attracting wasps. Many gall reports from other trees as well (elms, hickory, willow).
- Fruit and vegetable pests:
- Japanese beetles damaging grapes and fruit trees.
- Pear psylla and earwigs are active—especially at night.
- Indoor pests: Field ants and a rare case of bee moth (associated with old wasp nests).
