Powdery mildew or stripe smut. Need more information to determine which one. How do the affected grass blades look? What are growing conditions? Are these happening in shady areas? What are weather conditions? Control depends on more info also. Last time you fertilized?

How big is the garden? How many plants? Can you just dig them up one at a time? If you are dealing with maple roots, that may be what you have to do.

Is that 3/4' tall or 3 or 4 feet tall? I'm guessing 3 or 4 feet tall. Well, if you are allowed a wiener roast in your area then I would drill a few holes in the center. let some oil soak into the holes and then build a small fire on top of the holes. I make ash for my garden on a city lot by having a small campfire ring in my front yard. I burn some scrap wood, limbs, and firewood. next to me are marshmellow, and wieners, buns etc. I haven't been cited or checked on by the police or fire dept as I am attending the fire. Actually, campfires are allowed in the city if you follow certain rules. I keep it small but I do get some good ash for a compost pile and I know what went in there. Once you have a center hole burned in you could chip out a round hole or redrill and burn deeper.

Box Elder bug. Some people do vacuum them up which distrurbs them enough that the release that distinctive odor. My wife will trap them, gently, and flush them. As stated clearly in the link below do not use any insecticide in the house to control these wee buggers. In my case any thing that might control these would trigger an Asthma attack and make the house unhabitable for me for over a week. Here is a link that might be useful: Box Elder Bugs