By Christopher Vincent
Kaolin particle film is a non-toxic tool to reduce psyllids and increase tree growth. Particle films are nothing more than a suspension of solid particles that make a “film” on the leaves after they dry. They work mostly by reflecting light. Kaolin is the most common type of particle film because the clay is mined directly and can be used after very little processing. The result is trees that are healthier and less stressed, leading to higher yield.
Asian citrus psyllids find citrus trees visually. Particle films reflect light, but not in the wavelengths that psyllids need to identify a citrus tree. Kaolin is naturally white, and the natural color reduces the number of psyllids that land on trees. Films that have been dyed red hide the trees from psyllids even more effectively.
University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) studies have found greater than 80% reduction of psyllids in kaolin-treated trees relative to insecticide-treated trees.
Citrus trees cannot keep up with water demand in the Florida summer. To cope, the trees close their stomata, which heats leaves and reduces growth. Particle films can reduce leaf temperature by up to 10 degrees. At the same time, they redistribute light deeper into the canopy, allowing more shaded leaves to photosynthesize more. UF/IFAS studies show that leaves of kaolin-treated trees are not as water stressed as trees without kaolin. The red-dyed kaolin also reduced whole tree water use. The overall result is that trees grow faster and produce more fruit, even after being infected by HLB.
It is recommended to maintain constant coverage with particle films. Uninterrupted coverage helps keep psyllids out of the grove and keeps the trees cool and growing. UF/IFAS researchers are still testing what quantities of coverage are needed. But for now, the recommendation is the maximum labeled rate of 50 pounds per acre of Surround WP. If using red dye, the recommendation per acre is 35 pounds of Surround with 88 fluid ounces of red Colorback mulch colorant.
Christopher Vincent is an assistant professor at the UF/IFAS Citrus Research and Education Center in Lake Alfred.
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