Actually soil microbes get a boost following most agrochemical treatments. Remember Oftanol for grubs? The soil biologist girl at the CT Ag Station tried to tell me I was causing thatch by killing microbes. I agreed that chlordane caused thatch but Sevin or Diazinon? Never.
Well she continued along that train of thought through the 1980's then she was gone. She resurfaced in the news following the EXXON Valdeez incident.
She was part of the team of microbiologists that identified, cultured and bred bacteria that was used to clean up the spilled petroleum.
They learned of "enhanced microbial degradation" from Mobay (before Bayer). Their oftanol was failing miserably. Bacteria in the soil would gradually ramp up after every lawn care treatment. By the third consecutive season the bacteria population would be just large enough to eat all the Oftanol before the grubs could get their own toxic dose.
She never did thank us for the lessons.