Drones and dogs work together to save avocado crops

Invasive redbay ambrosia beetles, which first appeared in the United States in 2000, are native to India, Japan, Myanmar, and Taiwan. Although the beetles are not considered to be major pests in their native range, that is not the case in the US. There, the beetles are feared, because they transmit the raffaelea lauricola fungus, which causes a vascular disease in trees called laurel wilt.

This plant disease has already killed approximately 500 million wild laurel trees across coastal forests in south-eastern US. More than 90% of trees die within six weeks of infection, and the disease has a particularly devastating effect on avocado groves. That is a particular concern in South Florida, where commercial avocado crops bring in $55 million a year, and where the loss of avocado groves to laurel wilt disease could potentially invite replacement costs in excess of $400 million.

Detecting laurel wilt is a major challenge. Diseased trees can begin to wilt within two weeks, and by the time symptoms are visible, the fungus has likely spread to nearby trees via root grafting. This is a particular problem in commercial groves, where trees are planted close together.

Spotting infected trees

To contain the spread of the fungus a detection programme was developed by provost and executive vice-president Kenneth G. Furton and Professor of biological sciences DeEtta Mills from the Florida International University (FIU). The programme couples drone surveillance with canine scent detection. ‘This is not just a Florida problem,’ Furton says. ’From California to Latin America, there are growing concerns about how to respond to this aggressive disease.’

FIU’s hunt for infected trees begins with unmanned aerial vehicles (UAVs), which are far less expensive for fungus-hunters to use than manned helicopters. The UAVs carry thermal digital imaging instruments that are able to search for stressed trees from the sky. UAV-mounted spectral cameras are able to identify the unique spectral signature of laurel wilt and other stressors, allowing analysts to detect affected trees before symptoms are visible to the naked eye.

However, the deployed technology itself cannot identify the cause of the stress. That is where the dogs come in. Dogs have up to fifty times more olfactory receptors than humans, and can be hundreds to thousands of times more sensitive to odour. While drug-sniffing dogs may be better-known, dogs can be trained to detect a wide array of different odours for their handlers. FIU’s trained scent-detection dogs are able to detect impacted trees. By using drones to identify particular areas of concern in avocado groves, the dogs are able to search for affected trees in smaller, more manageable areas.

Removing diseased trees

After a dog alerts on a particular tree, researchers from DeEtta Mills’ lab carry out DNA analysis of samples collected from its main trunk or branches, allowing them to confirm that the tree is affected by laurel wilt. As of January 2016, the dogs with the help of UAVs have identified approximately 200 pre-symptomatic trees, all of which were later confirmed to harbour the fungus after lab testing. Currently, diseased avocado trees must be removed, along with those surrounding them. Already, more than 6,000 of Miami’s 74,000 avocado trees have had to be destroyed to contain the spread of the fungus.

FIU’s research into laurel wilt detection is funded by the Florida Department of Agriculture and Consumer Services, but the techniques FIU’s researchers are experimenting with, could be useful far beyond Miami. The unique detection programme could have far-reaching applications for the entire agricultural industry, including for the much-larger avocado industries in California and in many developing countries. The combination of research, technology, and the assistance from dogs could be the game-changer for the fight against this deadly fungus.

This article is adapted from other articles written by the authors, like the article ‘Dogs, drones battle deadly avocado fungus’ that was published on the website of the Florida International University (FIU). Original link: https://goo.gl/b1wNPW