Plague War by Jeff Carlson

Ruth, Cam and Newcomb were miles beyond any hint of green. The plague had been catastrophic in this place. Even the weeds and hardy sagebrush were dead. All that stood were a few stubs of windswept roots. Several times they'd seen the desiccated remains of grass and wildflowers laid on the ground like stains, brittle and black. In the heat, the insects had been destroyed, which in turn condemned the reptiles and the vegetation. Lacking any balance whatsoever, the biosphere had tipped. The earth baked into powder and superheated the air.