Using Drones in the Fight Against Apple Scab

By Rachel Rohr on October 28, 2013

Photography by Rachel Rohr

For apple growers in the eastern United States, the biggest problem – the most relentless, pervasive, unavoidable issue, which can ruin a whole crop if not managed aggressively – is apple scab. Researchers at the University of New Hampshire are working on a new tool to combat the apple scourge: A drone.

 The fungal infection causes dark scabby lesions on the leaves and skin of the apple, which leaves the flavour unaffected, but does effectively make it unsaleable.

“It’s a huge issue,” says Peter Wagner, owner of Applecrest Farm Orchards, a 110-acre orchard in south east New Hampshire. “Thirty years ago, you were allowed to have a scab on your apple that was probably 10 millimetres, or half the size of a dime, without a problem at all. Now you can’t put any of that in the apple pack, so it renders the apple unmarketable.”

Apple scab is less of an issue in drier regions, such as Washington state. But in places like New York, New Hampshire, Vermont or Massachusetts, apple scab is the number one pathogen and apple farmers’ primary concern.

In recent decades, researchers have made strides in understanding the fungus’s life cycle, so farmers are spraying less than they used to, with better results. Some farmers even use predictive models, such as the Dutch program RIMpro to forecast the best spraying times. But apple scab is still a persistent battle, and it’s especially difficult – if not nearly impossible – for organic farmers to grow a scab-free crop.

So researchers at the University of New Hampshire are working on a new tool for fighting apple scab: Drones.

“When you think about apple production now, a grower needs to walk through his orchard every day to make sure he sees any new insect pests or any new disease pests that come into an orchard,” says plant pathologist Kirk D. Broders, an assistant professor at UNH. “But when you’re talking about a 10, 20, 100-acre orchard, your ability to do that on a daily basis is almost impossible.”

But it is possible with a small unmanned aerial vehicle (UAV), or drone, carrying an infra-red camera that takes multi spectral images of the orchard. A computer program crunches the wavelengths in each pixel, making it possible to hone in on colours and temperatures – and locate apple scab.

“If you had a UAV that had the capacity to go up once a day, take a digital image or multiple digital images – both in infra-red and then in normal spectrum — you could actually monitor your orchard”

Broders says the ultimate goal is to develop an orchard-monitoring UAV system that could be sold to growers.

It’s not the first time that multi spectral imaging has been used in agriculture. Researchers have analysed plants using lab equipment, and large farming operations can hire air planes to fly over and take multi spectral images of large swaths of corn or soy beans to monitor crop health.

“What we are trying to do is develop a system that allows us to do things in-between – so not at the single-plant lab scale, and not at the air plane several-fields-at-a-time scale,” Broders said. “We’re trying to develop a low-cost system that could actually be used by either individual researchers or individual growers.”

At Applecrest Farm, Peter Wagner calls the prospect of an affordable infra-red imaging system that could be used daily, “pretty awesome.”

“I think that’s a great endeavour – no question – particularly the fact that most scab that we don’t eradicate usually occurs at the top of the tree,” Wagner said. “In the old days with big trees, you could climb up and look around – which is time consuming – but now with the new plantings, the trees are younger, smaller, and it’s harder to climb because the limbs aren’t as strong.”

Wallhead and Broders envision apple growers using the drone-camera system in conjunction with the predictive models for apple scab – the real-time data that tell farmers when to spray.

“The UAV is really only one tool we’re using to manage apple scab, because apple scab is so difficult to control,” Broders said. “We’re using our predictive model to improve application of organically-certified compounds. We’re using the UAV for early detection. And then whenever possible, we’re utilizing resistant varieties to also help us reduce fungicide inputs and provide better control.”

One scab-resistant variety growing in the experimental research orchard at UNH’s Woodman Farm is Crimson Crisp, the product of collaboration among Purdue University, Rutgers and University of Illinois.

While apple scab is the main concern in the eastern U.S., the multi spectral data can also be used to detect other problems – from insect damage to nitrogen deficiency. Pinpointed applications of fertilizer, pesticides and fungicides mean growers are using less, which is better for the environment and consumers – as well as the farmer’s bottom line.

The drones could even be used to monitor forest health, scanning for disease or invasive beetles.

“I think it has applications even beyond agriculture,” Broders said. “And I think there are a number of people that are just now beginning to understand what these unmanned aerial vehicles are capable of doing.”

Courtesy: Modern farmer.