You can kill them, and keep them off your plants with tobacco juice.
I know it sounds crazy... Buts its true. Google it. "Tobacco juice as an insecticide"
Just get some chewing tobacco... Like Red Man, Levi Garrett, Beech Nut, or whatever is the cheapest... Then empty the tobacco into a container then fill with water until it is completely submerged and let it sit over night. Then strain the liquid through a coffee filter, or hand towel, an old t-shirt. whatever is available. Squeeze out the solution Into a container and dilute it with water until its light brown... Put it in a spray bottle and spray your plants as needed. This is a cheap and organic way of getting rid of pests. and it works! It wont hurt your plants... The nicotine and other natural chemicals found in tobacco will kill and repel spider mites, aphids, and any other insects that can destroy your crops...