Effects of Radioactive and Non-radioactive Dust Upon Larrea Divaricata Cav., Nevada Test Site

Among populations of Larrea divaricata Cav., monitored for ionizing radiation exposure following nuclear detonations which occurred in July 1962 at the Nevada Test Site, two also sustained heavy coatings of fine-particle dust. All dust-covered plants eventually became defoliated during the following year; in those irradiated but not dust-coated, there was no defoliation. One of the dusted populations was exposed to 4000–6000 roentgens during this year, and the other to negligible dosages; defoliation and subsequent death of stems in the irradiated population was evidently the result, therefore, of dust effects and not the ionizing radiation. Defoliated plants have recovered or are recovering by basal and/or stem sprouts.