The constant waves of cold air keeping New Jersey in the deep freeze this month may be miserable for its residents, but may actually be a boon in the fight against one of the state’s most persistent pests — the Southern pine beetle. the bug has migrated north in recent decades and has been devastating 30,000 acres of the Pine Barrens, choking trees to death as they burrow deep into their trunks.

But temperatures reached a potentially magical minus 10 degrees in northern portions of the Pinelands last week and have been sub-zero on another occasion, leading to hopes that some of the population may have died off and could be more easily managed come spring.

What’s more, ricocheting temperatures — sometimes changing more than 60 degrees in 24 hours — may provide even more help, building then melting ice crystals inside the insects that could destroy their cells over time.

“If you have this freeze-thaw cycle within the insect, it’s more likely that they’re going to suffer cellular damage and die,” said Jim Fredericks, an entomologist with the National Pest Management Association. “The magic number for the pine beetle is minus 8 degrees. That, in and of itself, will kill some of those off.”

Experts say this will ultimately matter only if climate change, over time, doesn’t make this a losing battle.

The beetles are about as big as a grain of rice, and they burrow under tree bark to lay eggs. The tunnels they dig cut off the circulation of water and nutrients, strangling the tree in a matter of weeks, according to the state Department of Environmental Protection.

For years, the beetles stayed in Texas and points south because they cannot weather extreme cold. In fact, 90 percent of the critters die at minus 8 degrees Fahrenheit, said Matthew Ayres, a professor of biology and co-chair of ecology and evolutionary biology at Dartmouth College. For decades, the coldest night of winter kept the beetle well south of New Jersey.

Damage wrought by the Southern pine beetle in th ePort Republic Wildlife Management Area is shown in this 2010 file photo.

But as the state and the rest of the region went about 15 years without a crucial cold snap, the beetles drifted north. Now, their demarcation line is at the Pinelands, said Ayres.

“The coldest night of the winter keeps them at an edge,” said Ayres. “But in 15 years, if there are no cold events extreme enough to kill a species, it opens an area up to colonization.”

These past few weeks have been the first time since 1994 that temperatures have reached levels that could kill off a substantial number of the beetles.

It’s difficult to tell how much of the Pine Barrens reached 8 degrees below zero or lower last week, but Berkeley Township, on the northern fringe, reached minus 10 on Jan. 24.

Earlier in the month, readings between minus 3 degrees and minus 7 degrees were taken in multiple parts of the Pine Barrens, which Ayres suggested could kill between 35 and 70 percent of the insects.

The state’s estimates are more sobering. The Pinelands region didn’t get cold enough — and didn’t stay cold long enough — to have a big impact on the beetle population, said Ron Corcory, the state Forestry Service’s project coordinator for the Southern Pine Beetle Project.

Climate Change?

Shifts in New Jersey’s climate may ultimately make battling the beetle more difficult, however. David Robinson, the state climatologist at Rutgers University, said New Jersey has been warming for decades, and extreme cold has been harder and harder to come by.

“The rate at which our lowest extremes have risen has far outpaced our overall warming,” Robinson said. “We can’t say definitively why that is just yet, but certainly one of the possibilities you have to look at is climate change.”

Star-Ledger staff writer Stephen Stirling contributed to this report.

