Website: insectlab.russell.wisc.edu

PJ Liesch returned from vacation and shared observations from the past two weeks at the UW Insect Diagnostic Lab. While some insect activity is easing, several pests remain active across landscapes, gardens, and homes.

Landscape Pests

• Dogwood Sawfly: Still active and causing significant defoliation in some yards. Larvae feed on leaves  and pupate in soft wood, including cedar siding—an unusual behavior.
• Scarlet Oak Sawfly: Confirmed in a case with ~75% defoliation on a young oak sapling.
• Elm Zigzag Sawfly: Reports continue, with damage varying widely between trees.
• Bark Beetles: Found in stressed hardwoods like oaks and elms. PJ emphasized these are often  secondary pests, often appearing after environmental stress.

Turfgrass Pests

• Sod Webworm: Adults are active and visible at night. Damage is rare in higher-mowed lawns but may occur in low-cut turf like golf courses.

Fruit and Vegetable Crop Pests

• Plum Curculio, Codling Moth, and Apple Maggot: Active in apples, pears, and stone fruits. Damage often goes unnoticed by backyard fruit growers until harvest.
• Spotted Wing Drosophila: Still affecting late-season raspberries. PJ noted adults can continue to be spotted  into November.
• Stink Bugs: Brown marmorated and green stink bugs are being reported in both juvenile and adult stages.

Structural & Miscellaneous Insects

• Banded Tussock Moth: Numerous sightings of these fuzzy, yellowish caterpillars with long tufts. Not considered pests, but PJ advises caution when handling due to potential skin irritation.
• Floodwater Mosquitoes: Surged following Milwaukee’s recent flooding. Cooler temps may suppress activity, but warm weather could prolong the season.
• Gallinipper Mosquito (Psorophora ciliata): Large, aggressive biters reported in Milwaukee and Spring Green. Larvae are predators of other mosquito larvae. Not a major disease risk but memorable due to size and bite.
• Yellowjackets, Paper Wasps, and Bumblebees: High activity around structures and yards. Colonies are annual and will naturally die off in 4–6 weeks. PJ referenced a helpful fact sheet co-authored with UMN entomologist Jeff Hahn.
• Black and Yellow Garden Spiders (Argiope spp.): Common and conspicuous in late summer. Often mistaken for invasive Joro spiders, but native and beneficial.
• Black Widow: Rare but one was recently confirmed in Dane County. PJ planned to remove one from a mailbox for safety.
• Praying Mantids: Reports are beginning to trickle in as mantids reach maturity. Most sightings come from southern counties like Dane, Rock, Racine, and Kenosha.