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McHenry County report: 90 traps collect more than 17,000 spongy moths as counts dip slightly
Summary
County staff reported results of the 2025 spongy moth (Lymantria dispar) trapping program: 90 county traps captured more than 17,000 adult moths. Staff said counts are down slightly from 2024 in many areas but remained high in identified hotspots; the program is monitoring rather than eradicating populations.
Scott, a county staff member who presented the trapping report, told the Planning, Environment and Development Committee on Nov. 4 that the county deployed 90 traps in 2025 and recorded more than 17,000 spongy moths in those traps.
The report showed a wide range of catches: the lowest trap recorded four moths and the highest trap recorded more than 1,300. Scott said the county's totals were higher in absolute terms than last year partly because the county deployed more traps (90 in 2025 versus 65 in 2024), and that when adjusted for trap count the population appeared slightly down from 2024.
The program focuses on monitoring and mapping. "We deployed 90 traps this year," Scott said. "We collected over 17,000 moths in those 90 traps." He explained the county uses a heat map to locate hotspots and monitor trends, and noted many traps registered declines of 25% to 50% compared with the prior year, while some areas increased.
Scott told the committee that spongy moths (formerly called gypsy moths) are an invasive species that can defoliate more than 300 species of trees and that repeated defoliation can cause oak decline. He added that a single year of defoliation typically will not kill an oak: "one year of defoliation on an oak tree will not kill it," he said, and advised property owners to give trees time to recover before taking irreversible action.
Scott described the program as largely non‑interventional: county traps count and map populations rather than eradication. He said the county's trapping effort is modest in cost and staff time and credited the county board for responding to resident concerns after public reports in 2023. Scott also noted a transition in his role and that the committee should discuss the program's future oversight at a subsequent meeting.
Committee members asked about data sharing. Committee member Carl asked whether the county shares data with the state; Scott said the county exports GIS data to a national clearinghouse and that the information is incorporated into a larger monitoring effort.
Scott identified a recurring hotspot near East Crystal Lake Avenue: the Adams property recorded among the highest catches in both 2024 and 2025. He said residents in some areas have taken private control measures, including localized spraying, and that the county's program can help communities coordinate.
Scott urged vigilance from residents who move outdoor materials: egg masses can be accidentally transported on firewood or outdoor furniture. He described simple removal methods (scraping into soapy water) and said informational videos and guidance are available.
The committee did not take formal action on the trapping program at the Nov. 4 meeting; Scott recommended continued monitoring and further discussion about program stewardship after his role change.
