Problem At The Hive

Looking at the hive about an hour ago, it was evident that there was a problem.  There are always dead bees at ground level at the hive through natural attrition with the workers just living out their short life span but today the number visible (we usually sweep the ground cover about once a day to remove the dead) was tenfold normal.  After some observation and checking our bee book resources it seems to be one of two things - either robber bees are battling our hive or our bees have been harvesting on recently insecticide sprayed plants.  We are leaning toward the latter.  We have not used more than about one can - hand held - of spray on our property in over 30 years and we never have more or less invasive bugs.  That is nature doing its' thing.  Why people spray their blossoming plants is beyond me as the loss of bee colonies is always in the news.  Harmful sprays are a temporary fix but in the long run if the bees die out then so will our food supply.  Wake up ye sprayers of little faith.