This year we had very unusual weather!  Temperatures in February were far lower than normal, delaying bloom and initial peach twig borer emergence.  Also, during the PTB emergence there was rain and sometimes snow, making timing for sprays very tricky.  As you can see from the graph below, emergence this year was faster than the average, for February, then it slowed to the average at the beginning of March, then fell behind the average by the middle of March.