"As for the red sand that covers Baghdad when the seasonal khamasin winds blow, he said it does the plants no harm. In fact, it protects them from insects, because we cant afford to buy the pesticides or the proper soil.
It seems, from this excerpt, they don't even NEED pesticides. So, why did they have so much of the stuff? One of life's great mysteries, I guess. ;o)
I think we will know eventually!