Submersion as a tactic to prevent emergence of emerald ash borer Agrilus planipennis from black ash logs

Abstract

Abstract Black ash (Fraxinus nigra Marshall) trees are an important cultural resource and provide the wood used for traditional contemporary basketry by numerous Native American and First Nation tribes in the U.S.A. and Canada. The invasion and subsequent spread of emerald ash borer Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) threatens the ash resource in North America and the basketry tradition. Submersion of infested ash logs has been proposed as a potential tactic to control A. planipennis emergence, although the duration of submergence required to prevent adult beetle emergence is unknown. We assessed the survivorship of A. planipennis prepupae through adult beetle emergence in green ash (F. pennsylvanica Marshall) bolts submerged at weekly intervals for up to 6 weeks and in black ash bolts submerged at 4‐week intervals for up to 24 weeks. The moisture content of sapwood at depths where prepupal chambers are commonly found was quantified in the black ash bolts after 0, 12 and 24 weeks of submergence. Mortality of A. planipennis from prepupa to adult was low (5.7 ± 2.3%) for the first 6 weeks of submersion but rapidly increased to 100% in green ash and black ash bolts submerged for 8 weeks or longer. In black ash, the outer 1.3 cm of wood became highly saturated after submersion for 12 weeks (81.0 ± 4.5%) and moisture increased only slightly after 24 weeks (83.9 ± 2.8%). The results obtained in the present study indicate that A. planipennis prepupae in green ash and black ash bolts can survive complete submersion for extended periods of time (i.e. at least 6 weeks) and successfully emerge as adults afterwards. Logs submerged for at least 8 weeks, however, produced no live A. planipennis beetles, indicating that submersion represents an efficacious control option.