Regarding work to be done this month, you may want to stroll through your orchard, and pick (not fruit, but) caterpiller egg cases. Sound like fun? The following advice was found in the Illustrated Annual Register of Rural Affairs, edited by John Jacob Thomas, 1865:
"Work for February - Caterpillar's Eggs. - Pass through orchards and fruit-gardens with a basket on the left arm, and a knife or pruning-shears on a pole in the right hand, and clip off every shoot that contains a nest of caterpillar's eggs and carry them in the basket and burn them. Each nest contains several hundred eggs, (fig. 6,) and trees are now more easily and effectually cleared of them than after they have hatched and formed large webby nests. They encircle the young twigs near the extremities, and are thus easily detected by the practiced eye, and readily clipped off. A day should be selected for this work when the sky is rather dark, otherwise the eyes will be unpleasantly affected by the constant looking upward."
How’s that for an Integrated Pest Management (IPM) technique, ca. 1865? It's actually promoted today as an affective IPM method, particularly for those with a small orchard. But if you had hundreds of trees? Well, one can understand why The Heirloom Orchardist might have embraced chemical pesticides when they became available.
Today, a balanced approach is appropriate. The Tent Caterpiller seems to be the target in the above 1865 account. Another non-spray approach may be to wait until the eggs hatch, then go after the small caterpiller nest, before it gets too large. The nests are easier to see than the little shiny black egg clusters. But timing is critical....those tiny larva hatch just in time for bud break. They can cause quick damage to young leaves!