netting and pollen

does anyone know of any type of netting that could be placed over a crop that would prevent pollination by males? i've started some seeds for a OD grow this summer but live in a area highly infested with ditchweed. good for hiding them but bad for all the pollen flying around trying to make my little girls produce seed. it would also have to be able to be over the plants for a extended period of time (onset of flowering to harvest) and still let them breathe and recieve enough light.
thanks for any help!