Mike Roberts

Do Citrus Trees Have It Made in the Shade?

Did you know that too much sunshine stresses citrus trees and exacerbates the symptoms of citrus greening? While Florida boasts of being the Sunshine State, too much sunshine can have negative effects on citrus tree health and production. Observations of the healthy state of feral citrus trees in a shaded environment have led several groups of researchers with UF/IFAS to study the benefits of shade for Florida citrus trees. The results so far indicate that more shade would offer a host of benefits to Florida citrus trees, especially when it comes to mitigating the damages caused by citrus greening.


The Benefits of Shade for Citrus

In the ongoing study, which started in 2018, the UF/IFAS research team installed shade netting with 30 percent, 50 percent, or 70 percent shade over Hamlin trees already infected with citrus greening. Testing on those trees has shown improvements in health, leaf hormonal balance, metabolism of sugars and nitrogen, and less intense tree flushes. Researchers maintain that less intense flushes suggest longer leaf life and a reduction in leaf drop.

During the two years when the research was conducted, results show that the trees under 30 percent shade are producing double the amount of fruit of the citrus trees that are in full sunlight. Higher levels of shade also reduced tree stress but did not increase fruit yields.

Furthermore, laboratory testing has shown that Asian citrus psyllids, which spread citrus greening, have a reduced rate of landing on citrus trees in low light settings. The research is looking into whether that carries over into the fields. Similarly, citrus trees in wooded settings have been found to have few to no psyllids on them, few instances of infection with citrus greening, very few symptomatic leaves, and few signs of sun-caused stress.

Researchers have concluded that providing citrus trees with shade can potentially offer the following benefits:

  • Reduced leaf flush
  • Lowered Asian citrus psyllid load
  • Reduced starch accumulation
  • Decreased amount of citrus greening-symptomatic leaves
  • Reduced photoinhibition and photodamage
  • Increased leaf water status
  • Increased sucrose levels
  • Boosted phloem transport
  • Extended leaf life span
  • Improved fruit yield

In short, shade seems to reduce the stress on citrus trees, discourage psyllids, reduce the severity of symptoms of citrus greening, and improve yields.

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