These dogs can smell tree disease – and could help save the world’s orange groves


(Credit: Unsplash)

This article is brought to you thanks to the collaboration of The European Sting with the World Economic Forum.

Author: Rosamond Hutt, Senior Writer, Formative Content

  • Dogs detect diseased trees with about 99% accuracy.
  • ‘Citrus greening’ has caused 70% drop in Florida’s orange output.
  • The disease has spread to the majority of the world’s citrus-producing areas.

Dogs, of course, possess an incredible sense of smell. They can be trained to sniff out bombs, drugs and even diseases such as cancer, malaria, diabetes and tuberculosis.


Now, scientists in the United States are training dogs to detect a disease that is destroying the world’s orange trees.

Huanglongbing (HLB), or citrus greening, prevents fruit from ripening and eventually kills the tree. It is spread by a tiny insect called the Asian citrus psyllid.

First documented in Guangdong Province in southern China in the early 1900s, HLB is now found in the majority of the world’s citrus-producing areas.

In Florida, where the disease emerged in 2005, it has caused a more than 70% drop in the production of oranges. It has spread to Texas, California, Georgia and Louisiana and is threatening to wipe out the $3.35 billion US citrus industry.

Paw patrol

Currently, there is no cure. Early detection is vital; and farmers try to find and destroy infected trees as quickly as possible.

The problem is, trees can have HLB for months, or years, without showing symptoms. Meanwhile the disease spreads undetected through citrus groves.

But it turns out that canines are much more adept than humans at identifying the sick trees.

Plant epidemiologist Timothy Gottwald and colleagues at the US Horticultural Research Laboratory in Fort Pierce, Florida trained 20 dogs to sniff out Candidatus Liberibacter asiaticus, the bacterium that causes HLB.

Dogs tracking diseases in trees
The 20 dogs in the study picked out infected trees with 99% accuracy.
Image: Gottwald et al., (2019) in Proceedings of the National Academy of Sciences

Every time the dogs correctly identified the bacterium in a tree and sat down next to it the researchers rewarded them with play time with a toy.

The dogs were able to detect diseased trees with about 99% accuracy – within two weeks of infection, according to a paper published in the journal Proceedings of the National Academy of Sciences.


What is the World Economic Forum doing to help ensure global food security?

Two billion people in the world currently suffer from malnutrition and according to some estimates, we need 60% more food to feed the global population by 2050. Yet the agricultural sector is ill-equipped to meet this demand: 700 million of its workers currently live in poverty, and it is already responsible for 70% of the world’s water consumption and 30% of global greenhouse gas emissions.

New technologies could help our food systems become more sustainable and efficient, but unfortunately the agricultural sector has fallen behind other sectors in terms of technology adoption.

Launched in 2018, the Forum’s Innovation with a Purpose Platform is a large-scale partnership that facilitates the adoption of new technologies and other innovations to transform the way we produce, distribute and consume our food.

With research, increasing investments in new agriculture technologies and the integration of local and regional initiatives aimed at enhancing food security, the platform is working with over 50 partner institutions and 1,000 leaders around the world to leverage emerging technologies to make our food systems more sustainable, inclusive and efficient.

Learn more about Innovation with a Purpose’s impact and contact us to see how you can get involved.

By comparison, a DNA-based test – the only US Department of Agriculture-approved method for confirming the presence of HLB – detected less than 3% of infected trees at two months.

Gottwald’s research suggests using sniffer dogs combined with removal of infected trees is the most effective way to suppress the spread of the disease, and would allow the US citrus industry to remain economically sustainable for another 10 years.

Vital protection

About 80% of the world’s food comes from plants. But, as with Florida’s citrus trees, they’re under constant threat from pests and disease, according to the Food and Agriculture Organization of the United Nations.

Some 40% of global food crops are destroyed by this threat every year. And such problems can be impossible to wipe out once they’ve taken hold.

The UN has named 2020 its International Year of Plant Health to raise awareness of how protecting plants from disease can help end hunger, reduce poverty, protect the environment and boost economic development.

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