Mike Roberts

Research Delves Into Use of Kaolin Clay Against Greening

A recent webinar that was a joint effort by the University of Florida Institute of Food and Agricultural Sciences and the University of California looked at the results of current research into the benefits of kaolin clay in fighting citrus greening. UF/IFAS’s Christopher Vincent and the University of California at Riverside’s Monique Rivera teamed up to host the webinar on using kaolin to fight both citrus greening and Asian citrus psyllids, the vector that spreads citrus greening. They shared the results so far from their ongoing research into the use of kaolin clay.

Research Results for Kaolin Clay

Vincent maintained that kaolin clay is a mixture of clay particles suspended in water. The mixture is sprayed on citrus tree leaves to completely cover them in the film. The mixture reflects light, shades the tree, redistributes sunshine throughout the canopy, reduces sunburn, and essentially masks the leaves—especially during times of flush—from Asian citrus psyllids looking to feed on the leaves.

Research is ongoing for both white kaolin clay, which is commercially available to Florida citrus growers, and red kaolin, which is not. Vincent and Rivera maintained the research has shown that kaolin clay deters Asian citrus psyllids from feeding on citrus trees, delays citrus greening infection, improves tree growth and yield, improves water use efficiency, reduces sunburn, improves leaf water status, and mitigates water deficits.

While white kaolin is available commercially to growers, the research has shown that it is not as effective as red kaolin. Researchers have found that white kaolin does not hold up as well as red kaolin during periods of rain, and that it would more than likely need to be reapplied more often than red kaolin. Red kaolin simply has a red dye added to the clay mixture. Research has shown that red kaolin is more effective at managing Asian citrus psyllid populations and citrus greening, has a greater benefit in improving growth and improves water use efficiency in addition to being a superior product when it comes to rain fastness.

The researchers maintained that while kaolin clay does deter Asian citrus psyllids from feeding and delays citrus greening infection, it does not offer protection forever. All of the citrus trees in the research were infected with citrus greening after two years. However, kaolin clay could be used to extend the time a citrus tree is free from infection, such as after Individual Protective Covers (IPCs) are removed, giving citrus trees that much more time to grow and be productive.

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