Hi Rich, Many thanks for your thoughts. You are always a huge and appreciated expert contributor to the Pestlist!
I guess my thinking was less to destroy the worms and more to remove a preferred food source through de-thatching. I realize it’s not quite like vacuuming to remove dust food for moths but I guess I was hoping the strategy would translate. The property is large so if we made it less hospitable near the house could we get the earthworms to migrate far enough to keep the emerging parasitic flies from finding their way to the house? I think I know the answer but thank you for indulging the thought exercise! We’ve near exhausted exclusion and trapping efforts with unsatisfactory results. This is an interpreted historic house so there is hesitance for larger scale exclusion interventions which get costly and might not look right. How bad does it have to get? These are questions for further up the chain. Many thanks again! Adam From: pestlist@googlegroups.com <pestlist@googlegroups.com> On Behalf Of Pollack, Richard J Sent: Tuesday, October 1, 2024 9:14 AM To: pestlist@googlegroups.com Subject: [PestList] Re: Cluster fly control through non-pesticide earthworm control? Adam, This is an interesting question. I doubt that efforts to dethatch the lawn nearby will measurably diminish the abundance of cluster flies that enter the house. I am skeptical that the tines of the dethatching device will reach sufficiently deep into the soil to kill many worms. Even if the device destroyed a significant number of worms on the property, it would do nothing to those on abutting properties. Cluster flies can and do fly far enough that local management of this kind will likely fail. The adult flies tend to accumulate on the southern- and western-facing exterior walls, and follow the rising shadow as the sun sets late in the day. They’ll find small openings around soffits, windows, and siding, and then enter the wall voids. Once inside, they’ll follow the light they may see to enter the human-occupied spaces. I’d advise that you consider sealing or screening exterior penetrations on the building, particularly those just below the roof line. If the building is not insulated, consider blowing cellulose insulation into the exterior wall cavities. These efforts should not only reduce opportunities for flies to enter, but also improve the energy efficiency of the structure. Best of success. -Rich Richard J. Pollack, PhD Senior Environmental Public Health Officer Environmental Health and Safety (EH&S) | Harvard Campus Services 46 Blackstone Street., Cambridge, MA 02139 C: 617-447-0763 www.ehs.harvard.edu<http://www.ehs.harvard.edu> [A blue and black logo Description automatically generated]<https://www.linkedin.com/in/richard-pollack-6818997/> From: pestlist@googlegroups.com<mailto:pestlist@googlegroups.com> <pestlist@googlegroups.com<mailto:pestlist@googlegroups.com>> on behalf of Adam Osgood <aosg...@historicnewengland.org<mailto:aosg...@historicnewengland.org>> Date: Tuesday, October 1, 2024 at 9:02 AM To: pestlist@googlegroups.com<mailto:pestlist@googlegroups.com> <pestlist@googlegroups.com<mailto:pestlist@googlegroups.com>> Subject: [PestList] Cluster fly control through non-pesticide earthworm control? Hi All! We’ve had some ongoing and significant cluster fly challenges at one of our house museums that is impacting the collections and visitor experience. Understanding that cluster flies are parasitic to earthworms we are thinking of ways to manage the worms and as result, hopefully reducing the fly population in a non-toxic way. I understand that de-thatching a lawn can remove organic material which earthworms eat and can be effective in controlling them. My Question: Does anyone have knowledge or experience in de-thatching a lawn as a successful means of cluster fly control? Many thanks and happy hunting everyone! 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