
Purdue's forestry extension ties Indiana willow dieback to drought plus Cytospora, Botryosphaeria, and Colletotrichum cankers that race through drought-stressed wood, showing as chlorotic foliage, thinning branch tips, bark splits, and black lesions on green stems. Stress is a willow that yellows and sheds leaves in an August dry spell and refoliates the next spring; dying is dead scaffold limbs in the upper crown with cankered bark — and fungicides do not help, because the fungi live inside the wood where sprays can't reach.
The "willow" on a central Indiana quote is almost always a weeping willow somebody planted 25 years ago near the wet back corner of the lot, and it's now over a fence, a shed, or a septic field. It is one of the few species where an arborist will lead with removal rather than pruning options, because the wood is brittle, it seals wounds badly, and it is usually structurally finished before it is old.