Researchers from the University of Florida have developed a sensor to detect citrus greening in trees, which could give growers the vital early warning they need to save the rest of their crop.

University of Florida researcher Alireza Pourreza using the sensor

The portable sensor has been in development since 2010, when preliminary tests were conducted in citrus groves and promising results led the scientists to take the idea further.

The sensor, which is now in its second prototype stage, is capable of immediately detecting whether or not a tree is infected with the disease with an accuracy of 95-98%.

"This is a portable, real-time sensor, so we can take images in the field and then the sensor can tell the user on the spot," biological engineer and project collaborator professor Daniel Lee told www.freshfruitportal.com.

Lee said the sensor was an improvement on traditional ground inspection methods largely due to the technology's speed and accuracy in making the detections for citrus greening - also known as HLB.

"With ground crews it is time-consuming, labor-intensive, and sometimes subjective, but our sensor can provide growers with a fast, easy, and accurate way to detect the disease," he said.

He added another round of seasonal testing would likely be necessary to verify the sensor's performance, and a sponsor was still needed to 'bring the technology to life', but after that the sensors would become available to growers.

Scientists have been unable to find a cure for citrus greening because infected plants are difficult to maintain, regenerate and study.

However, the researchers used the fact that starch in leaves 'rotates' light that is shined onto it, and the fact that HLB-infected trees had a higher starch concentration than normal.

Therefore, if the light is rotated sufficiently the machine will inform the user the leaf being sampled has tested positive for citrus greening.

Another positive aspect of the technology is its low cost. Researchers used 10 high-powered LEDs and an inexpensive camera to assemble the sensor for less than US$1,000.

The sensor can either be used as a hand-held device or it can be mounted on to a vehicle and driven between the citrus groves. Lee said the optimal detection distance was around 80cm.

Citrus greening first begins when a sap-sucking insect deposits bacteria on the leaf of a healthy fruit tree. The bacteria invade the tree and starve it of nutrients, causing its fruit to be shrunken and misshapen with a thick, pale peel. Most trees afflicted with citrus greening die within a few years.

In Florida - one of 10 states that have been quarantined due to the presence of the bacteria-carrying insect - commercial citrus acreage decreased by 28% from 2004 to 2011, with HLB one of the major reasons for this loss.

University of Florida researchers are also working on the eradication of the bacteria-carrying insect that causes the disease, and breeding citrus rootstock that show better greening resistance.

www.freshfruitportal.com