By Fernando Alferez and Osbaldo Vasquez
As individual protective covers (IPCs) are being adopted as a standard management practice to protect newly planted citrus trees from psyllid infestation, it has become apparent that one of the main effects of this tool is improved tree growth. Trees under IPCs grow larger with thicker canopies. This is probably the result of healthier trees that perform better because they don’t allocate resources to fight with the greening disease. It may also be the result of some mild shading that improves vegetative growth and the effect of less evapotranspiration due to the special environment that the IPC mesh creates.
University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) researchers have determined in different trials that the vapor pressure deficit is lower under IPCs than in the surrounding atmosphere. This results in less evapotranspiration in the covered trees.
These observations have been done in trees where IPCs are zip-tied at the bottom. However, many growers are not zip-tying the bags. They leave the bottoms open (Figure 1A). This has advantages as installation of the covers is faster and less labor intense. In addition, a loose bottom may allow some beneficials to enter the canopy while reducing some secondary pests. However, the impact of this practice on the environmental conditions inside the bag and its effect on tree growth has not been studied.
Zip-tying may have some implications not only for tree growth but also for irrigation frequency and water-use efficiency. To address these questions, UF/IFAS researchers are conducting several trials. So far, they have seen that vapor pressure deficit is indeed significantly different when comparing zip-tied or open-bottom IPCs (Figure 1B). It is still too early to determine if more frequent irrigation will be necessary in open-bottom IPC trees to achieve the same growth as in zip-tied IPC trees. This information is currently being collected and will be available soon.
Fernando Alferez is an associate professor, and Osbaldo Vasquez is a biological scientist, both at the UF/IFAS Southwest Florida Research and Education Center in Immokalee.
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