Clay Spray is a super fine natural kaolin clay (very pure at 97-99% kaolin).  Mix with water (it quickly forms a suspended slurry) and use in a sprayer to apply a film over the leaves and branches of your plants, until just at drip point (when the spray has fully covered the surface, and begins to drip or run off).  Rinse spray equipment immediately to avoid clogging.

500gms makes up to 10L of spray when mixed with water - so a little goes a long way.  Avoid using when rain is imminent, as the spray needs to dry.(50gms = 2/3rds of a cup/160mL to 1L of water)

The white residue on your plants will weather off and will need repeat treatment every 2-3 weeks (check visually when spray has noticeably gone).  Repeat at 50% strength approx. fortnightly for best results.

Originally used by orchardists to protect young trees and vegetable crops from heat stress and sun damage, studies have shown kaolin spray is effective in reducing citrus gall wasp numbers, and other pests.  The spray clogs up mouthparts and makes it difficult for the adults to pierce bark for egg laying (in the case of citrus gall wasp), and disrupts the laying of eggs.  (Some evidence exists that it is useful in controlling leafhoppers, stink bugs, codling moth and thrip.)

For citrus gall wasp, weather conditions may alter when you need to apply - but it's generally from September to mid October - when the larvae emerge and the breeding/egg laying cycle is beginning again.

When used as a 'sunscreen' on plants (eg. tomatoes, capsicum, avocado, grapes, mango, stonefruit, cucumber, melons) it reflects damaging UV rays but allows light to enter the leaves (so does not stop photosynthesis or block stomata - the 'breathing' openings).

Kaolin is a completely natural product - fine grade clay is typically used in cosmetics, toothpaste, some foods and paper manufacture.  It can be simply washed off your fruit when harvested.

Clay Spray powder is a fine mineral - avoid using in windy conditions and use a dust mask when handling.