What Caused Damage To Bear Naked Cypress Mulch?

Question

4/28 installed cypress mulch. 5/14 yard people came sprayed mixture of systemic insecticide & liquid fertilizer & blanket herbicide. Next day it looked like the mulch that meets grass line was burnt. The fertilizer guy never saw this before Do you know what caused this? Thank you

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Answer 1

If the mulch had been stacked in piles too high, producing sour mulch (very low pH), the burned area typically is the grass, not the mulch. Sour mulch produces chemicals that may have reacted to all the chemicals applied to the grass.