Drones have become an increasingly important part of “precision agriculture,” a state-of-the-art method for micro-targeting farm inputs – seeds, fertilizer and pesticides – to areas of a farm property where soil fertility promises the highest crop yield.

Rather than planting seeds or administering fertilizers and pesticides the length of the farm, precision agriculture helps farmers identify the most vital and distressed areas and then carefully distribute their scarce and expensive farm inputs accordingly.

The method, based on a combination of aerial mapping and AI-enhanced sensor technology, yields enormous cost and time savings.  Not only are fewer inputs wasted, but the need for expensive fixed-wing aircraft and human farm labor is eliminated. In addition, since fixed-wing airplanes are gas-powered, drone use is also more sustainable.

The need for drone-based precision agriculture is especially great in Hawaii, where the fate of several leading fruit industries is being threatened by insect infestations and rapidly spreading plant diseases. Since 2020, the College of Tropical Agriculture and Human Resources (CTAHR) based at the University of Hawaii in Oahu has developed an ever-expanding precision agriculture portfolio that includes a full array of crop protection activities.  CTAHR’s current portfolio includes:

Automated inspection of pineapple crops.  Ripe pineapples need to be harvested quickly to present crop loss.  The collapse of the pineapple industry in Maui has left Oahu as the only Hawaiian island with a significant acreage of pineapples.  CTAHR, with funding from the US Department of Agriculture’s Small Business Innovation Research program, is testing a fleet of drones that can speed the field inspection process while sharply reducing labor costs.  The project, which began in  2021,  uses deep learning-based density-estimation approaches to count the number of flowering pineapple plants in a field block.  Drones can repeat the process periodically at minimal extra cost and can monitor  disease and weed growth, applying fertilizer and pesticides, as needed.

Use of Essential Oils to Battle Pests.  CTAHR researchers and extension faculty have also been collaborating with certified organic producers in Hawaii and four Southern mainland states to evaluate the effectiveness of essential oils as a deterrent to major fruit toxins such as avocado scab, anthracnose (fungal disease), and powdery mildew in a variety of fruit crops.  The arrival of the lace avocado bug in 2021 has further jeopardized the vitality of Hawaii’s $3 million avocado industry.  The four-year project, now in its third year, received a $2 million grant from the U.S. Department of Agriculture’s National Institute of Food and Agriculture.   More funds are being sought as the disease threatens to expand to other lucrative Hawaiian fruit crops, especially mangos.

Protecting the Macadamia Harvest.   CTAHR is also studying the effects of an Australian native insect on leaf and branch decay, flower loss and even tree death among Hawaii’s macadamia trees.  While essential oils tested in a counterpart CTAHR study identified their potential for reversing decay, this study actually measured the devastating economics of macadamia nut disease from a single invasive pest that has swept the Hawaiian Islands in recent years.  CTAHR believes its proposed remedy , if adopted widely, could restore the vitality of the  $63 million industry, preventing its threatened collapse.

Spraying Palm Trees to Eliminate Beetles.  The latest CTHR project targets an invasive species of rhinoceros beetles that infests Oahu’s vast acreage of coconut palm trees.  The research team conducted some early tests with a new pesticide – dubbed “Demon Max” – on coconut palms at a posh country club on Oahu.  The drone sprayed  targeted aerial applications of the pesticide atop 53 coconut trees that showed signs of infestation as well as a smaller group of trees in more advanced states of decay.  The team collected dozens of beetles killed or seeking to escape and used GPS and metadata collected by the drone to identify the trees subjected to “Demon Max” to facilitate follow-up treatments at 3-month intervals.  Currently, the rhinoceros beetle infestation is limited to Oahu but researchers and industry experts fear it could spread and threaten Hawaii’s only native palm species, which is already endangered.

All of these drone applications could go a long way to relieving Hawaiian agriculture’s growing pest and disease problems.   The main obstacle, experts say, is the state’s continuing difficulty in getting a drone industry off the ground.   The number of farms in Hawaii regularly using drone technology remains small, according to Suzanne Shriner, executive director of the Synergistic Hawaii Agriculture Council.  A 2019 Department of Agriculture survey found that 182 drones were being used in Hawaii’s agricultural sector overall, but another 872 were wanted.

High labor costs are pushing farmers to consider drones but fear of technological change and a lack of training and infrastructure to support their use outside of academia are limiting the industry’s growth.  Time is of the essence:  A number of the state’s farm industries (including sugar cane)  have all but collapsed in recent years, in part due to weak crop yields, and without improved crop protection, other industries now being studied by CTAHR could well disappear in the coming years.

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