Determine Tree Health With Canopy Assist

Josh McGill HLB Management, Technology, Tip of the Week

By Amit Levy and Tripti Vashisth

Many Florida citrus growers are currently injecting oxytetracycline, spraying gibberellic acid (GA) or treating trees with enhanced nutrition. A new program offered by the University of Florida Institute of Food and Agricultural Sciences (UFIFAS) Citrus Research and Education Center (CREC) can help growers determine if these treatments are improving tree health and leading to higher yields.

This program, called Canopy Assist, is based on the finding that the density of the canopy is correlated with the yields. That is, the higher the tree canopy density, the higher the yield. So, measuring a tree’s canopy density can evaluate the health status of the tree.

With Canopy Assist, you don’t need any special instruments or complicated operations. Since this method is based on photos taken from your smartphone, all you need is your smartphone and a selfie stick.

The first step is to take four pictures from underneath the tree canopy, with the phone camera facing up to the sky, so it will take a picture of the canopy. The four pictures should be taken from four corners of the tree (Figure 1). The second step is to upload the pictures onto a UF/IFAS database.

Canopy Assist
Figure 1. A: Taking pictures of the canopy is done by a smartphone attached to a selfie stick. Pictures are taken from underneath the canopy facing up, from four corners of the tree. B: ImageJ threshold analysis of the picture determines the density of the canopy (red).

Researchers at UF/IFAS CREC will then analyze the canopy coverage and provide a report. The way they do this is by using ImageJ software threshold function to separate pixels from foreground (canopy) and background (sky), and to find the percent coverage of each photo. This number will determine if the trees are on the healthy side or on the sick side. Additionally, by flagging and reanalyzing the trees throughout the year, growers will be able to know if the treatments they provide are improving tree health or not.

Here are a few recommendations for using Canopy Assist:

  • More trees are always better, but at least five trees per block are needed.
  • When selecting the trees, either do it randomly or select the trees that represent the block.
  • April–May and October–November are the suggested times for this analysis.
  • Use this link or scan the QR code below.
Canopy Assist

Amit Levy is an assistant professor, and Tripti Vashisth is an associate professor, both at the UF/IFAS CREC in Lake Alfred.

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