Yes, Milky Spore is harmless to food crops. It is not a chemical pesticide. It may be used in gardens, around pools and wells.

Milky Spore Powder in cans is a one time application put down in spots in measuring teaspoon amounts every four feet apart creating a checkerboard pattern of spots throughout your yard. Each spot contains 100 million spores.

 Milky Spore Spreader Mix in bags is applied with a drop spreader over every square foot of grass and requires applications in spring, summer and fall for two years to build the number of spores in any one area to millions of spore

Chances are those patches are caused by snow mold which is a turf fungal disease. Often these patches measure from 3 to 12 inches and can combine so that there are no apparent individual patches at all. There are steps you can take to prevent this from happening. As we approach the end of the mowing season, lower your mower deck to successively lower settings so the deck will be at it lowest setting (without scalping the grass) for the last 2 or three mowings. Be sure to remove or mulch any leaves that cover the grass in the fall. Grass left too long or that is smothered by leaves provides ideal conditions for the eruption of snow mold in the spring when we experience cool temperatures and moist turf.