No ‘killing frost’ yet

To destroy mosquitoes
Thu, 10/31/2019 - 4:45pm
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“No killing frost yet.”

Al Gettman, coordinator of the Rhode Island Department of Environmental Management's Mosquito Abatement program, told The Times that a “killing frost,” a frost that destroys mosquitoes, has not yet occurred. In order for a killing frost to do its job and kill mosquitoes, the temperature must remain below 32 degrees for three consecutive hours.

According to a Rhode Island Department of Health press release, “While the National Weather Service issued a frost advisory for Rhode Island on Oct. 4, temperatures in most Rhode Island communities likely did not reach the threshold for the first ‘hard frost.’ RIDOH does not monitor the frosts throughout the state, and since a hard frost occurs in different parts of the state at different times, local officials are asked to consult weather resources to determine when a hard frost has taken place. Although mosquitoes are not killed until a hard frost occurs, mosquitoes become less active at temperatures below 58 degrees and they become largely inactive when temperatures fall below 50 degrees.”

The concern is that with continuing mild weather, mosquitoes that could be carrying eastern equine encephalitis, a deadly virus known as EEE, are still alive and capable of infecting people. That’s despite the fact that health officials claim most EEE infections occur during the summer months.

Gettman said it’s been “an extremely unusual year” regarding the increase in EEE cases. The virus has been diagnosed in six states, leading to five deaths.

The virus was responsible for the death of a 50-year old Warwick, Rhode Island man on Sept. 8. The virus was detected in some samples taken from Block Island on Sept. 13, but has not been detected since.

Bill McCombe, co-director of New Shoreham’s Emergency Management program, told The Times on Monday that there have been “no new positive tests” of EEE reported on Block Island. McCombe said John Swienton, the island resident responsible for capturing mosquito samples, “just finished collecting” some samples that were sent to the Rhode Island Department of Environmental Management laboratory.

Mosquito testing runs from June 1 through October each year. 

When the killing frost occurs it’s a positive sign, meaning that mosquito populations have been destroyed, or are on the decline.

A killing frost, or hard freeze, typically occurs in mid-to-late October in the northeast.

Gettman noted that although a killing frost is effective, and the “risk (of EEE infection) reduces with cooler temps, warm winter days can bring out a few hibernating adult mosquitoes.”  

Health officials urge the public to be vigilant about protection from mosquitoes at dusk and dawn, taking precautions, including wearing long-sleeved clothing and applying insect repellent.