particle films

Protect Trees With Particle Films

Daniel CooperHLB Management, Tip of the Week, Weather

particle films

By Christopher Vincent

Particle film is a useful tool to take the edge off stress to citrus trees caused by weather and HLB. University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) research over the past several years shows moderate concentrations of kaolin particle films cause trees to grow faster, suffer less water loss and keep leaves cooler, even when affected by HLB. Particle films also repel Asian citrus psyllids.

particle films
New sweet orange fruits and leaves along with red-dyed kaolin particle film applied with carnauba wax product six months ago

In young trees, researchers saw dramatic increases in growth and yield during the first three years of growth. This was partly due to particle films delaying HLB infection. However, particle films caused trees to grow faster even after they were infected. Researchers imposed moderate water deficits to mimic what HLB does to trees and found that the trees with particle film were able to better maintain leaf water and keep their stomata open longer for more growth and photosynthesis. This effect is strongest in the dry months of spring and the hot months of summer (March-October).

Particle films are simply a suspension of microscopic solid inert particles that can be sprayed onto leaves. When the suspension dries, it leaves a film of particles on the surface of the leaf, which reflects light away from the outer leaves of the canopy. This causes the outer leaves, which are usually stressed by high light, to be partly shaded. Particle films also can increase the light deeper in the canopy, where leaves are usually shaded.

White particle films are best for increasing light penetration into the canopy, while red-dyed films are best for shading and for reducing psyllids. Therefore, it is recommended to use white films when temperatures are more moderate (spring and fall) and red films when high temperatures are straining the trees more (summer).

Some shade is good, but too much can suppress growth, so researchers are working to identify the best rates. Currently, it is believed that 12 pounds per acre of white Surround kaolin particle film is best in March–May and October–November, while 17 pounds per acre of red particle film is ideal for June–September.

Using Raynox, a carnauba wax-based product, in 1:1 ratios with kaolin helps the particle film stay on the leaves through more than 20 inches of rain. Using Raynox means reapplication is only necessary after new growth covers the old growth.

Make red particle film by mixing in 2.5 fluid ounces of red-colored Colorback mulch colorant for each 1 pound of Surround kaolin particle film. Applications are not recommended in the cooler months of the year.

Christopher Vincent is an associate professor at the UF/IFAS Citrus Research and Education Center in Lake Alfred.

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