Website: insectlab.russell.wisc.edu

PJ Liesch shared another active week at the Insect Diagnostic Lab, with seasonal shifts influencing pest activity across Wisconsin.

Landscape Pests

• Fall Webworm remains highly visible across the state, especially in northern and southeastern Wisconsin. While dramatic in appearance, damage to large, established trees is generally negligible. PJ reminds folks that aggressive pruning or burning of webs is unnecessary.
• Sawflies continue to be active:
  • Scarlet oak sawfly reports have continued, but overall impacts to plant health have been minor.
  • Elm sawfly was observed on alders, though it can feed on a wide range of hosts including elms, birches, and willows. Larvae are large (1″+), typically yellowish with a black dorsal stripe or occasionally salmon-colored.
  • Dogwood sawfly larvae have generally finished feeding and are getting ready to overwinter. 
• Galls are generating many ID requests:
  • Oak rough bullet galls on bur oak stems and branches  are common.
  • Other leaf galls are also being reported, but PJ notes these are mostly cosmetic and will resolve with leaf drop.
• Leaf miners on oaks were identified in collaboration with DNR colleagues. No major trend noted, but the diversity of leaf miners (14 insect families) makes identification complex.

Fruit and Vegetable Crop Pests

• Stink bugs (brown marmorated, green, and brown) are active in gardens. PJ also noted predatory stink bugs (subfamily Asopinae), which feed on caterpillars and other pests—beneficial allies in the garden.
• Fruit damage assessments are underway:
  • Plum curculio and codling moth damage are evident in harvested fruits.
• Woolly aphids are active on apple, crabapple, and hawthorn trees. Late summer and early fall are peak times for sightings.

Structural & Miscellaneous Insects

• Dogwood sawfly larvae are burrowing into soft wood materials like cedar siding while pupating. Though not structurally significant, they can damage trim and siding.
• Jagged ambush bugs (a type of assassin bug) are being reported. These native predators blend into flowers and may prey on pollinators. PJ emphasizes their ecological role and recommends plant diversity to support pollinators.
• Praying mantids (Chinese mantis) sightings continue in southern Wisconsin—typical seasonal activity.
• Dog Day cicadas are still being reported. PJ clarifies these are annual cicadas, not the periodical ones seen last year.