I reached out to Diane Alston, Professor of Biology at Utah State University. Pest insect control is one of her specialties. I asked her about the infestation of bugs on the Playa, and this is what she had to say:
The large green insects look like the Say’s stink bug. I looked online and found some reports of high numbers of this stink bug in areas of Nevada in past years:
The above article indicates that populations of the Say’s stink bug increase on a weed called tumble mustard. They are a seed-feeding stink bug. Insecticides such as carbaryl (Sevin) and permethrin (many brands) will kill them on contact and reduce numbers in a local area, but they won’t make a dent in the large numbers that are flying into the playa from the drying weeds and desert plants. I’m certain that the large amount of lights that are run at night during Burning Man are a major contributor to attracting them to the site. You can replace white light bulbs with yellow or amber lights. Sodium vapor lights are much less attractive to insects than white lights. I don’t know how practical this is given the likelihood of a large number of lights at the festival, but it could help in a local area if yellow lights were used instead of white.
I don’t know of any repellents for stink bugs. I doubt that DEET products would work, but you could try it. They aren’t blood feeders, but seed feeders. Bites come from them stabbing their straw-like mouthparts into the skin as a protective behavior to ward off predators/harm. Wearing long sleeves and long pants would keep them off of your skin.
I don’t know exactly how long high numbers of the adults will hang around, but it shouldn’t be more than 2-3 weeks. What you are witnessing is a large influx of adult Say’s stink bugs that have developed on mustard weeds and other host plants in the vicinity and they will be dispersing to host plants to lay their eggs or find protective sites to spend the winter (not sure if they will have another generation this year).
So they aren’t harmful in that they are out to bite you nor are they are transmitting a disease organism on their mouthparts. They are just trying to disperse and your lights are attracting them. They are biting you to defend themselves.
Enjoy the wonders of nature, and good luck with Burning Man!