Oak Leaf Compost for HLB?
Researchers have been working for years to find a treatment for the devastating Citrus Greening disease also known as Huanglongbing or HLB. Now in 2020 there are two promising new treatments that are showing exciting results. Both are naturally occurring and can be easily applied to the trees and/or soil. One is even easily available to homeowners.
Finger Lime Protein
Finger limes are a distant relative to our sweet oranges that have a really interesting fruit. The fruit is shaped and about the same size as a finger. Inside the fruit is not the typical citrus. Instead of segments with juice vesicles, it is just the juice vesicles that look like caviar. It is a specialty crop with very thorny stems that some growers were trying because of the demand by chefs who use the juice vesicles to garnish dishes and to rim fancy cocktail drinks. The plant is tolerant to HLB. Researchers in California trying to find what made it tolerant to this devastating disease found a protein in the plant that confers tolerance. A protein that can be isolated and applied to other citrus trees in sprays seems to help the trees fight the disease. The genes for this protein have also been determined and may be used to breed new tolerant citrus trees. This exciting find stimulated lots of new research to determine just how effective this protein is and how it can best be implemented. The tree is not hardy outside in central Florida, but more information on this interesting plant is available.
Oak Leaf Compost Tea
The other new option with lots of potential for homeowners is right in our landscapes already. Researchers noticed that citrus trees under or near oak trees seemed to grow much better and have fewer HLB symptoms. This stimulated work on whether it was the shade (and thus reduced stress) that provided the benefit or something else from the oak trees. With the idea that some chemical may be leaching out of the oak leaves and either falling on the citrus leaves or on the ground around the citrus trees and affecting the disease, researchers decided to test extracts. They took laurel oak leaves and soaked them in a bucket overnight. The next day they filtered out the leaves and applied the “compost tea” as a spray to the leaves and as a soil drench under the citrus trees. To their amazement, this compost tea soil drench appeared to help the citrus trees recover from HLB symptoms. More work is needed to determine the exact extent and why this works, but it is something that any homeowner can try to help save their citrus trees.
Less Stress Still Key
The trees still need to be kept as stress-free as possible with the use of frequent light fertilizer or controlled release fertilizer and frequent light irrigation (don’t start fertilizing your trees now though – they are normally fertilized February – late September so they are not stimulated to grow when the new growth could be damaged by frost). The soil pH should also be kept at 6.0-6.5 and micronutrients supplied. However, you can also create your own oak leaf compost tea and apply this water to the root zone. Or, if this seems like a little too much work, just rake your oak leaves under your citrus trees. Don’t let the mulch come up against the trunk, or you could get foot rot, but under the drip zone is good. Live oak and Laurel oak both seem to contain the disease-fighting principle.
Citrus are iconic backyard trees for Florida and finally we have some hope to overcome this devastating disease in an easy and natural way. Try oak leaf compost tea on your citrus and let us know how it works for you.