3 years ago we had 1.5 inches of rain around the 4th of july.............No more till September.    It wasn't extremely hot that year untill Sept, but it was the first and worst Aphid infestation weve had so far. (knockin on wood).   We started on July 18th, had to respray 800 acres............Sorry to say, but the numbers were there the first time.  Am sure farming within 1-2 miles of buckthorn (Minnesota river) valley has something to do with it.

We have 120 acres sprayed so far, will look on Monday, am thinking a few more feilds will need it then.

Am using Lorsban.

Personal opinion is University (MN) numbers are too high for economic threshold, and weather has little to do with aphids in my part of paradise. 

:^)

Good Luck