Comparing the toxicity of two fumigants to insects from the field vs laboratory – does insect origin matter?
The golden-haired bark beetle, Hylurgus ligniperda (F.), is a common forest insect which may be associated with pine (Pinus radiata D.Don) logs exported from New Zealand. We tested the dose-mortality responses of H. ligniperda adults, from two different origins (field vs laboratory), to methyl bromide (MB), the most widely used fumigant worldwide; and to ethanedinitrile (EDN), a potential alternative to MB. Naked insects were fumigated with either MB or EDN at 10°C for 4 and 3 hours, respectively. Laboratory adults had been reared on artificial diet under controlled conditions for >10 generations. Field adults, by contrast, had been recently collected from Lindgren funnel traps with lures of alpha-pinene and ethanol. Tolerance to the two fumigants tested was significantly different, according to the origin of the insects, with field-collected adults being less tolerant to MB and EDN than laboratory-reared ones. The implications of our results for the development of disinfestation schedules for New Zealand export logs will be discussed.