Imagine if your spray equipment could tell where the pests were in your orchard so you could treat only the infested parts of the trees, rather than the whole orchard.
Ted Batkin, president of the California Citrus Research Board, told Washington tree fruit growers that this could soon become a reality, and if it does, it has the potential to reduce the use of spray material in orchards by 90 percent.

The Washington Tree Fruit Research Commission and the Citrus Research Board are jointly funding an effort by scientists in California to develop a robotic harvesting system. The two-part system has a scout, which uses cameras to map the location of the fruit, and a harvester that picks the fruit based on the data from the scout.

During a Fruit School on Competitive Orchard Systems, presented by Washington State University Extension and the Tree Fruit Research Commission in January, he reported on a companion project that the Citrus Research Board is sponsoring.

Scientists are developing a sensor that will be mounted on the scout so that as it moves through the orchard it can analyze volatile organic compounds (somewhat like distress signals) given off by the trees, and detect changes that might indicate if the trees are infected by disease.

The sensor, which is called a differential mobility spectrometer, might also be able to pick up volatiles that insects and mites give off to determine if the trees are infested, he said.

Artificial nose

The scientist working on the sensor, with this in mind, is Dr. Cristina Davis in the department of mechanical and aeronautical engineering at the University of California, Davis.

The sensor is proven technology, Batkin said. Such "artificial noses" are already used for detecting explosives and narcotics, and by the oil industry for detecting ­hazardous vapors.

They are relatively inexpensive and easy to maintain. However, they are larger than the one envisioned for detecting orchard pests. The sensor that Davis is developing will be about the size of a deck of cards.

Batkin said a basic version of the sensor, which would look for easy-to-detect volatiles, such as pheromones, should be ready to test in the field this year. It will then be refined to detect other volatiles.

Further refinements

The sensor could continue to be updated as data on new organic volatile compounds comes along, he said. "As you get new metabolic markers, you just feed them into the system. You don’t have to create a new system. You just plug the new data in, and you’re up and running almost instantly."

Batkin envisions that the sensor would be mounted on the scout near the cameras, and the data would go into the same database as the pictures to produce not only a photographic image of what’s going on in the orchard, but a volatile reading indicating what’s going on in the plant.

"Imagine a system that could go through with the VOC [volatile organic compounds] sensors and only spray the part of the orchard where the pest in fact was," he said. "If we could only spray parts of the tree where the pest infestation was, we could reduce our spray material by 90 ­percent and only use 10 percent of the pesticide we’re using today. This is where we’re trying to go with this ­technology."

Batkin said the focus of the research so far has been on detecting the volatiles and determining the absence or presence of pests. How to spray the orchard would be the topic of further research. The scout might work in tandem with a sprayer, or it might have its own spray nozzles, for example.

"There are some very creative people out there, and who knows what we might end up with," he said.

According to McFerson, the Research Commission is funding research on an ethylene sensor and supporting work on volatile chemicals that would be of interest in sensing.

Fallen behind

Batkin said specialty agriculture has fallen behind other industries in terms of engineering advances, with the exception of the grape industry, which has been using mechanical harvesting for more than 20 years. Producers of specialty crops became complacent because they had adequate labor and everything was working well as it was, he said.

"Now, we’re in the process of playing catch-up, and the good news is the industry has been able to attract a number of high-quality engineering schools to bring their technologies to the ag sector."

With increased funding for agricultural research, colleges such as Carnegie-Mellon University, Massachusetts Institute of Technology, Olin College of Engineering, California Polytechnic State University, and Harvey Mudd College are looking at agriculture as a potential outlet for their engineering studies, he said.

"Agrobotics is where they want to go with these things. We’re getting spin-off from an entire new sector of engineering and design that will fit into our agriculture scheme.

"We may be behind a little bit, and we may not be where we would like to be," he added. "But in the next five to ten years, hang around, and put on your seat belts, because it’s going to be a heck of a ride. I’m excited about where we’re going to go in the next ten years and I think you will see each year more high-tech technology applied to the ag sector."