EM overnight, how low can you go?

This has been a cold spring for Lakes Region Cow Hampshire. That has delayed leaf development and has skewed start date for spraying. Another has been a string of overnight lows during the past week in the upper 20's. I have many overnights in the low forties and one in the high thirties forecast. If I can get a spray in, should I bother adding EM? Will they survive that low and still be Effective?

Excuse my ignorance, but what is "EM" and why would you add it to a spray?

Thanks in advance.

Effective Microbes. EM-1. The main competitive component in either a spring or seasonal spray. The part we brew from concentrate from a commercial source, of which, I contract [www.teraganix.com] to ship me a cube each spring.

Lakes Region NH @ 1200' or so
5a?

393 planted towards a 440 goal mixed apple, pear, plum and apricot...