Mite-Induced Bud Gall in Globemallow

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At the Nevada Test Site an abnormality was observed in branch tips and young leaves of a globemallow, Sphaeralcea grossulariaefolia (Hook. and Am.) Rydb. In infested plant parts, terminal internodes are shortened, and the dwarfed leaves are crumpled, forming conspicuous bud galls. The windborne mite which causes the gall is identified as the crumple or bud mite, Acalitus sphaeralceae Keifer (Eriophyidae). Within the terminal plant growth, the female lays eggs and feeds on embryonic tissues, injecting saliva and aspirating the liquefied plant material. Subsequently the leaf grows into the crumpled condition, providing crevices which the immature and adult mites inhabit and producing enlarged nurse cells upon which both young and adults feed. Leaves become modified predomi- nantly by folding over, enclosing these surface parasites which do not enter the mesophyll. In leaves involved in gall formation the mesophyll, normally closely packed palisade, develops as loosely arranged spongy tissue. Considered an invading weed species, the perennial Sphaeralcea grossulariaefolia is common at sites of mechanical soil disturbance. Within the Nevada Proving Ground, it grows primarily along road- sides, in bladed areas and peripheral to atomic ground zeros. In 1957, a terminal stem and leaf distortion was observed only in the vicinity of a balloon shot test area, Hood Ground Zero 9. Balloon shot sites were the most highly irradiated areas within the Nevada Test Site (Shields et al., 1963). In 1958, the abnormal condition was found in a number of mallow plants in the vicinity of a tower ground zero approximately five miles from the Hood shot area. In affected plants, crumpled dwarf leaves form terminal clusters which persist after the abscission of normal leaves (Fig. 1). In July, 1959, more than 250 Sphaeralcea were marked by numbered stakes at three ground zeros and along roadsides in Yucca Flat. The abnormality was present in approximately half of this number. In April, 1960, only one of the 38 surviving marked plants was affected. By late July, only nine plants remained, all nor- mal. These were largely along drainage lines, suggesting that two successive drought years contributed to the population decrease.