Insects, instead, would be destroyed selectively. Effects on Plants . Plants in general have a higher tolerance to radioactivity than animals do. Nevertheless, a gamma-ray dose of 10,000 rads would devastate most vegetation in the United States. As a general rule, large plants are more vulnerable to radiation than small ones.
Trees are among the first to die, grasses among the last.
The most sensitive trees are pine and the other conifers, for which lethal doses are in roughly the same range as those for mammals. Any survivors coming out of their shelters a few months after the attack would find that all the pine trees still standing were already dead. The lethal doses for most deciduous trees range from about 2000 rads of gamma-ray radiation to about 10,000 rads, with lethal doses for 80 percent of deciduous species falling between 2000 and 8000 rads. Lethal doses for grasses on which tests have been done range between 6000 and 33,000 rads, and a good deal of grass would therefore survive, except where the attack had been the most direct. The Effects of Nuclear Weapons.