Frequent irrigation with good quality water can improve fruit growth and development and overall productivity.
By Tripti Vashisth
HLB-affected citrus trees have small and weak root systems. Though the roots are efficient in taking up water and nutrients, there are not sufficient roots to support the tree’s canopy requirement. Therefore, the trees often experience water and nutrient deficit.
Not all HLB-affected citrus trees experience the same impact. The more severe the HLB symptoms, the higher the root loss and water deficit compared to trees with mild HLB symptoms.
The water deficit exacerbates during spring. This is often the low rainfall period in Florida and coincides with significant growth in trees (flowering, fruit set, fruit growth and leaf growth), which requires high water availability.
Recently, University of Florida researchers have found that severely HLB symptomatic trees have lower fruitlet retention than that of mildly HLB symptomatic trees. Another interesting finding is that fruit of severely symptomatic trees are on average smaller than mildly symptomatic trees.
Additionally, there is a link between fruit size and fruit drop. Small fruit are more prone to drop from the tree compared to large fruit. The growth of fruit can be attributed to cell division and enlargement, which increases the number and size of cells, respectively, during the first two months following the beginning of fruit set (stage 1 of fruit development) and about four to six months thereafter (stage 2).
Fruit size increases rapidly as a result of water accumulation in cells during fruit development. Therefore, adequate water supply during spring and early summer (the low rainfall period) is critical to ensure uninterrupted fruit development and growth for better fruit retention.
Water quality is equally important along with irrigation frequency. Citrus growers should make sure that the irrigation water is low in bicarbonates and has optimal pH.
Tripti Vashisth is an assistant professor at the University of Florida Institute of Food and Agricultural Sciences Citrus Research and Education Center in Lake Alfred.
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