Using drones and computer analysis appears to be a quicker and more economical way to carry out crop surveys at the start of a pest moth outbreak than conventional ground surveillance.
That’s the conclusion of an international study, which compared the use of drones to ground surveys in assessing damage by the beet armyworm (Spodoptera exigua) to soybean fields in South Korea.
The drone-based approach used a three-step process, involving capturing images using a rotary-wing drone equipped with a camera, downloading images and ‘stitching’ them together to create composite image, then analysing the damage using geographic information and image software. The ground survey involved a team of 19 experts selecting 30-50 plants from each of 31 blocks of the crop.
Accuracy, speed, value
The researchers found that the use of aerial images provided a crop damage assessment of comparable accuracy to the ground survey, while further analysis showed that the approach was more time efficient overall and more cost effective when more than 15 blocks of soybean are the subject of the survey, largely due to a reduction in labour costs.
“Another advantage of aerial surveys is that it can provide valuable information in the form of maps that show the distribution of insect damage. These maps can be used to guide where to conduct intensive surveys and management in the outbreak area, as well as to inventory the areas of damage,” the researchers wrote in the journal Insects.
“A digital inventory of insect outbreaks can be a useful resource for predicting and preventing future outbreaks, especially in the case of pests such as S. exigua, which have a history of occurring and damaging a wide variety of high-value crops.”
Satellites have wider role
The team also looked at how satellite imagery could be used to assess an outbreak on a regional scale. They found that it is effective in identifying hotspots of defoliation by the insects over a large area, but that is difficult to narrow the data down to individual blocks of the crop, while weather conditions can hinder the quality of information gathered in this way.
An alternative approach that could be used for early detection of beet armyworm outbreaks in the future is with the use of Doppler weather radar, said the scientists, with the technology not yet available to growers and pest control companies.
A mix of drones and satellite imagery could make a positive contribution to pest-management strategies, they suggested, in the face of potential large-scale destruction by S. exigua.
“By swiftly assessing the magnitude of outbreaks and identifying areas requiring urgent management, rapid responses to further damage can be achieved,” they added.