In a University of Florida research project, kaolin clay was shown to perform better than foliar insecticides against psyllids. The clay, which changes a leaf’s reflectance, may confuse the insects and prevent them from identifying sprayed leaves as a food source. It also physically affects insects that do land by sticking to their tarsal claws, which impedes their ability to stay on a leaf and feed. Kaolin clay could be an important tool in a grower’s pest control rotation, especially as some psyllids in Florida have shown resistance to neonicotinoids.

The clay must be able to remain on tree leaves, but the study showed coverage persisted through 3 to 5 inches of rain, making it a potentially useful tool in certain seasons or in drier climates like California.

Some growers have used kaolin suspensions for years to control aphids. Adding bentonite to the spray mix improves the clay’s adhesion to plant leaves.

Kaolin clay on citrus leaves

Source: University of Florida
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