According to researchers in Florida and California, kaolin clay, especially red kaolin, aids in the management of Asian citrus pysllids (ACP) and the HLB they spread, among other attributes. Christopher Vincent of the University of Florida Institute of Food and Agricultural Sciences and Monique Rivera of the University of California at Riverside recently presented a webinar about kaolin. The University of California Agriculture and Natural Resources hosted the webinar.
Vincent started by discussing white kaolin. “It’s available. It’s effective in Asian citrus psyllid management. It delays HLB infection,” he said. “It improves growth. It has some limitations in terms of efficacy during high-flush periods and it has a challenge with rain fastness.”
Vincent said red kaolin, which is white kaolin with red dye added, is even more effective at managing ACP and HLB. “It offers a greater improvement in growth,” he said. “We think it improves water use efficiency … It overcomes a few of the challenges that we see with white kaolin, like the challenge with rain fastness.” Red kaolin is dyed that color, Vincent explained, because researchers believe that the color red can enhance the effect of reducing the arrival of ACP on trees.
Kaolin is used as a particle film, which Vincent described as “just suspensions in water of particles that are then sprayed on the leaf to form a film on the surface of the leaf. What they do is they reflect light and through that reflection of light you get shading of the leaf … and you also get some redistribution of light into the canopy … They are also used to reduce sunburn.”
Researchers saw “much lower” HLB infection early on in trees coated with white and red kaolin as compared to trees treated with foliar insecticides and untreated trees, Vincent said. But two years after all trees were planted, they were infected with HLB, he said, “which is pretty standard here in Florida.”
Rivera echoed Vincent’s statements about kaolin in ACP and HLB management. She said both white and red kaolin increase tree growth and yield. She added that in Florida, kaolin treatments improved leaf water status and mitigated water deficits. “That is going to be increasingly important in California, as we all know,” she said. She noted that in California “there are continual water wars going on, and any way that we can create more efficient irrigation is going to benefit everyone.”
The kaolin research is funded by Florida’s Citrus Research and Development Foundation and California’s Citrus Research Board, noted Rivera.
Learn more about Vincent’s work on kaolin.
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