Can Laser Technology Save Ailing Citrus Trees?

Scientists at the University of Florida are hoping to improve on laser technology so that farmers can improve the efficiency of the spray solutions they use to restore vitality to greening-affected citrus trees. 

More efficiency would also mean reducing the amounts of chemicals. Citrus in India has been known to suffer seriously from certain disorders resulting in low production, twig dieback, slow death and even sudden wilting attributed to “dieback”, a disease that was first observed in the 18th Century in central India. Proof for the presence of HLB in India was eventually obtained at the virus Research Center at Poona by Capoor and co-workers, when they succeeded in transmitting the HLB pathogen by the Asian psylla, D. citri by demonstrating that trees with dieback symptoms invariably proved positive for HLB. Thereafter, it was reported from different citrus growing regions of India and was considered to be principal cause of citrus dieback disease.

From several surveys conducted from 2007 to 2012 along with molecular test (real-time PCR) in 16 states of India confirmed its distribution in all studied states (except Arunachal Pradesh): Andhra Pradesh, Assam, Karnataka, Madhya Pradesh, Maharashtra, Manipur, Meghalaya, Mizoram, Nagaland, Punjab, Rajasthan, Sikkim, Tamil Nadu, Tripura and West Bengal.  

Apart from India, the world wide in China, Africa, Philippines, south-east Asia, Pakistan, Nepal and America the disease Citrus Greening Disease Management also known as Technological Advances in Huanglongbing (HLB). Although HLB was first reported from China in 1919 where many citrus species were originated most scientists believe that citrus species are not the original host of the HLB organism. 

A tree infected with HLB in the field usually develops one or more yellow shoots with other parts of the tree healthy or symptomless. The affected leaves develop a pattern of yellow and green areas lacking clear limits between the colors, giving a "blotchy mottle" appearance. This is the most characteristics foliar symptom and the patterns are asymmetrical on the two halves of the leaf. Leaves can also become thicker, with veins enlarged and corky in appearance. 

Professor of Horticultural Sciences Ed Etxeberria at the UF Institute of Food and Agricultural Sciences explains that the updated technology has a laser shooting infra-red energy pulses at citrus tree leaves. That energy cracks the cuticles on the leaves and increases the penetration of agrochemicals -including bactericides- into the leaves by more than 4,000 percent. 

“We have vastly improved the basic parameters of the technology by using different laser wavelengths and other optics to make this a much more user-friendly technology, not to mention its increased efficiency and lower cost,” Etxeberria said. “We’ve made it a lot more effective.” The waxy cuticle on the leaf naturally prevents sprays from penetrating citrus leaves. The laser exfoliates the wax, creating cracks in the cuticle, thereby letting substances reach the undisturbed living cells underneath the leaf’s surface. 

In the lab, the new technology works like a charm. Etxeberria predicts the updated laser technology will be very simple to use in the field as well. But first, UF/IFAS agricultural engineers will have to adapt the laser to grove conditions.