By Tripti Vashisth, Taylor Livingston and Jamie Burrow
Canopy density is one of the most effective measurements to assess tree health of HLB-affected trees. Canopy density accurately distinguished between high and low fruit-producing trees in field trials, whereas CLas Ct value has been found to not be correlated with fruit yield.
Many new tools such as nutrient management guidelines, plant growth regulators, trunk injections and others are being used to improve the health of HLB-affected trees. With these tools, it can be a challenge to assess if tree health is improving by a visual basis alone. Canopy Assist is a free program offered by the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) Citrus Research and Education Center (CREC) to assess the canopy density of trees over time via digital image. By quantitatively monitoring tree canopy density over time, you can determine if the tools you are using are having a positive or negative impact and therefore make informed management decisions.
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 dos and don’ts for photo collection for canopy analysis can be found here.
Figure 1 shows an example where a grower has been evaluating the canopy of five trees to assess the efficacy of the fertilizer. The graph shows the trees seem to be improving in growth characteristics (canopy density) over time in response to the fertilizer treatment. Thus, the grower is encouraged to continue the current fertilizer program as this steady improvement in canopy density is expected to improve fruit yield.
UF/IFAS encourages growers to use this program to help with objective tree canopy assessment.
Tripti Vashisth is an associate professor, Taylor Livingston is a biological scientist, and Jamie Burrow is an Extension program manager — all at the UF/IFAS CREC in Lake Alfred.