Last week I read two contrasting things about potassium and Microdochium nivale (fusarium patch or pink snow mold).

In the March Greenkeeper International, this article about fusarium patch instructs one to:

Feed turf by all means - but with fertiliser formulations rich in potassium to make the most of the ‘gatekeeper’ nutrient with its intrinsic abilities in good water relations and strengthening of grass plant tissues.

There was also this, from Doug Soldat, showing an interesting result in which M. nivale was increased by potassium application:

Snow mold post was pretty popular today, so here's a combined pic. Numbers are lbs K2O/M/yr. pic.twitter.com/rTVG0jOrzd

— Doug Soldat (@djsoldat) April 2, 2014

When it comes to potassium application, one should not think that adding potassium will always "strengthen" the plant or improve resistance to diseases. Eliminating a potassium deficiency is almost always a good thing. Eliminating the deficiency will improve root growth, increase leaf growth, and ensure that the grass is able to function normally. Adding potassium beyond the amount required to eliminate the deficiency may cause problems.

• dandelion increased by potassium application
• snow mold increased by potassium application
• foliar disease of bermudagrass increased by potassium application

Because too little potassium is problematic, and too much can also cause a problem, the approach to potassium fertilizer that seems most likely to optimize turf performance is this one - supply the potassium the grass requires, but only that amount.