How do I know which fruits and vegetables have the least amount of pesticides? 

The Environmental Working Group has updated their Dirty Dozen/Clean Fifteen  https://www.ewg.org/foodnews/full-list.php  list – your best guide for which fruits and vegetables are the most and least contaminated. The list helps you decide whether to buy organic or not. When shopping, remember to also take into account the distance your produce has traveled and if you are supporting a mega (albeit organic) factory farm or a small local farmer. Farmers markets are opening soon and will have safety protocols in place.