Modified atmosphere treatments as a potential disinfestation technique forarthropod pests in greenhouses

Incidental transport of arthropods on plant material can be a significant m ode of pest entry into greenhouses. We evaluated the use of controlled atmo sphere treatments as a potential way to eliminate arthropod pests on plant propagules (i.e., cuttings or small rooted plants). Lethal exposures to CO2 or N-2 were determined for common greenhouse pests including fungus gnat l arvae, Bradysia sp.: green peach aphid, Myzus persicae (Sulzer); sweetpotat o whitefly, Bemisia sp.: twospotted spider mite, Tetranychus urticae Koch; and western newer thrips, Frankliniella occidentalis (Pergande). We also st udied the effect of pest species, life stage, and presence or absence of pl ants on efficacy of modified atmosphere treatments. Finally, effects of mod ified atmospheres on plant quality were evaluated for several bedding plant species including begonia, Begonia semperflorenscultorum Hort. 'Cocktail S eries', chrysanthemum. Dendrandhema grantliflora Tzvelev., geranium, Pelarg onium X hortorum L.H. Bailey, and impatiens, Impatiens wallerana Hook f., a nd among cultivars of geranium and chrysanthemum. Exposure for 12-18 h to > 99% N-2 or CO2 caused complete mortality of aphids, mites, thrips, and whit eflies. Fungus gnat larvae were more tolerant of hypoxic conditions. Adult mites and eggs were equally susceptible. For most pests, there was no diffe rence in response to atmospheres modified by CO2 or N-2. However, there was variation in response among plant species and cultivars, with effects rang ing from delayed flowering to mortality. Despite tile possibility of advers e effects on some plants, this work indicates that use of modified atmosphe res has potential to eliminate arthropod pests on plant propagules before t hey are introduced into greenhouses.