Please, polar vortex, ice these garden pests

For all the forecasters' frothing about the recent deep freeze, I'm hoping it means one thing: We get a break from some of the awful arthropods that stand in the way of total gardening nirvana. Deep freezes have an ability to knock back populations of insect pests we could do without.

I'm thinking of highly destructive or nuisance pests such as the brown marmorated stink bug and emerald ash borer.

The stink bug splits into two basic types: the hipster urban stink bug that squats in our (heated) houses, specifically the spaces between the walls. The other is the Birkenstock kind of stink bug, which stays in the woods and spends winter beneath the bark of dead trees. This lifestyle choice might prove costly.

"The ones in the woods are probably suffering some mortality," said Tom Kuhar, a professor of entomology at Virginia Tech. That would be good, because this pest does a lot of damage to fruits and vegetables.

More invidious, arguably, is the emerald ash borer, which has now spread to 22 states and threatens to do to the American ash tree what the chestnut blight did to the American chestnut - that is, virtually wipe it out.

The EAB, as it's known, "is the worst forest problem in our lifetime," said Whitney Cranshaw, an entomologist at Colorado State University.

The pest kills the tree by tunneling into the sapwood as a grub; it is in this state that it spends winter, protected from predators and the cold. "Even if it might be 5 degrees outside, a wood borer in a tree may not get to that temperature unless it persists for three, four, five days," he said.

Other factors come into play: Insects are chemically at their most naturally cold-hardy now; they would be less so in November or March. And as with plants, a blanket of snow forms a protective barrier against lower air temperatures, whether the insect spends winter as an egg, larva, pupa, or adult.

If the polar vortex genie gave me three insect (death) wishes, well, I have a little list.

The first horror afflicts not plants, but gardeners: It's the noisome Asian tiger mosquito, which since its spread in recent years has become a constant irritant from June to October. It's small, black and white, sneaky, and persistent. It is not a mosquito of the swamp or forest, but another urban beast and one that can reproduce in something as small as a discarded bottle cap.

It doesn't like extreme cold, so will this month's freeze reduce our repellent use in 2014?

Dina Fonseca, a scientist with Rutgers' Center for Vector Biology, told me that in the laboratory, at least, the eggs of the tiger mosquito perish below 10 degrees Fahrenheit - they simply dry out at that temperature.

"In principle, if all the eggs were exposed to the air temperatures we had, they would die," she said. But eggs protected by snow, soil, or leaf litter might not die, she said. If we get a particularly wet spring, and if people are not diligent about removing sources of standing water - too few are - a decimated population of the tiger mosquito could quickly rebound.

"It would be great if this kind of weather could kill off this mosquito," Fonseca said, "but my fear is that once they become established, it would take an extreme event for them to disappear."

Like what, I wonder - an asteroid destroying the Earth? A new Ice Age? I've stocked up on DEET and less effective botanical concoctions.

The second member of my despised threesome is the Mexican bean beetle, which in spite of its name seems perfectly OK with a mid-Atlantic winter, hibernating and dreaming of a steamy August. Once you have a nice display of beans - green beans, lima beans, asparagus beans, it doesn't seem to matter - the pest can just show up and quickly explode in population. I doubt the recent frigid spell will bother them too much. The pest is found all the way to the Canadian border and beyond. The adult beetles have a measure of antifreeze in their veins, and they are good at finding winter shelter.

We might have more luck with a Southern dandy, the harlequin bug. It is defiantly beautiful in its calico markings of black, yellow, and orange, because it wants predators to know that it is distasteful. How does it become distasteful? By feeding on cole crops and absorbing the plants' chemicals.

This cold winter, one hopes, will set them back. But as with the bean beetle, it is a good idea to do a thorough cleanup of the garden before spring arrives to deny the pests their shelter. The remnants of bean vines, the last of the winter kale, the lingering mustard greens, all these should be pulled and bagged. Whatever else this winter has in store, it has only eight weeks left to run.

Kuhar, of Virginia Tech, pointed out that the same polar vortex that kills off bad insects can also affect good insects such as ladybugs, which feed on aphids. Nature might be beautiful, but like winter weather, it's also complex and unpredictable.