General Information on Flour Preparation
Flour mixed in water is said to be very effective against aphids and spider mites. It should be applied in the morning taking care to spray underside of leaves. As the heat of the sun increases, the mixture dries out and the insects are left encrusted in flour, shrivel and die. The coating of flour falls off the leaves so that their ability to photosynthesise is not essentially affected (Stoll 1988).
According to Ellis and Bradley (1992) starch like ordinary baking flour is an old pest control remedy, whereas numerous products made as non poisonous insect control from potato starch, are currently on the market in the US and India. Reportedly potato starch apart from killing aphids, red spider mites, white flies and thrips also acts as an inhibitor to downy mildew on cucumbers in glasshouses.