Many commercial greenhouses now use soap regularly because whiteflies and green peach aphids have become so resistant to standard greenhouse chemicals.
Soaps act by impairing the waxy layer of insect exoskeletons.
This results in desiccation and eventual death of the insect. Sulfur Sulfur can be used for spider-mite control and will control some other mites which are resistant to miticides. The two-spotted spider mite, however, is resistant to sulfur. Sulfur acts by competing with oxygen in the blood stream. Horticultural Oils Various horticultural oils are also considered alternative chemicals.