My solar-heated greenhouse has a minimum temperature of 32oF and no pests of any kind. It supports all the mealy-bug afflicted species mentioned. A brave gardener might well leave plants outside to face a number of sub-40o nights, keeping a careful eye on the weather reports, with the reasonable hope that pests will at least be significantly slowed down. I can give no estimate of how long an exposure would be necessary, but really, there seems little reason to crank the greenhouse temperature above 40o in any case. Jim Jones Lexington, MA