With commodity prices depressed and the passage of a new farm bill lingering, farmers are having to sharpen their pencils with razor-like precision to remain economically viable. Simply put, they are looking to reduce input costs and protect their yield as much as possible.

Shelly Pate Kerns, LSU AgCenter corn specialist, is working on what she believes may be an answer to some of these issues. She is investigating whether Normalized Difference Vegetation Index technology can be used for early detection of diseases and developing a prescriptive management plan via the use of spray drones.

NDVI technology has proven to be useful as a pest management tool, and Kerns believes it has potential for monitoring and mapping foliar diseases.

“This is the first year of the study, which involves two on-farm sites in Franklin Parish,” Kerns said. “Most farmers tend to spray a preventative fungicide at tassel, R1 or right before tassel, but growers sometimes do not get that return on investment because the whole field might not need an application and disease pressure varies year to year.”

According to Kerns, when corn is close to entering the dent stage it is probably not economically feasible to treat disease symptoms unless disease pressure is extremely high.

Another problem incurred when fighting diseases is the physical constraints on a maturing cornfield. Later applications typically must be flown on because of the height of the corn, adding a cost to the application. Physical constraints also limit the ability to scout the whole field.

Here is where NDVI and drones may become part of the answer.

“Using NDVI technology will allow you to get a more complete field view because of the difficulty scouting a tasseled, tall corn field,” Kerns said. “Drone services could provide both scouting and spraying options, especially if the disease is limited to a very small area.”

Kerns said farmers are showing more interest in using drones for scouting and spraying because of the difficulty of spraying cornfields. Some farmers are considering buying drones for both purposes. Farmers also have the option of hiring a drone service to perform these tasks.

In Kerns’ study, she is using five different spray strategies to evaluate their economic impacts based on NDVI imaging. The strategies are:

1. An automatic spraying of the entire field at tasseling
2. A threshold treatment, meaning spraying the entire field when disease severity has reached the recommended level to warrant a treatment
3. An aggressive fungicide application spraying entire field at first sign of disease
4. An aggressive “hot spot” plan treating only those areas when the disease appears
5. An aggressive threshold treating only the hot spots as shown by NDVI that have reached the recommended level for treatment

The corn trials will be harvested with yields being measured, and disease ratings and number of fungicide treatments will be recorded. An economic analysis will be performed among each of the spray strategies to determine if fungicide cost and yield associated with NDVI prescriptive sprays had any economic benefits.

She also will be able to do a cost analysis of a spray drone application versus an aerial or spray rig fungicide application.

While there are some encouraging signs during the first year of the study, Kerns is quick to admit she has found some issues regarding using NDVI technology.

“Curvularia can be harder to pick up early with NDVI because the lesions are small,” Kerns said of one type of fungus. “Sometimes it will not be noticed until lesions overtake the leaves.”

Kerns said that northern corn leaf blight would be more likely to be picked up by NDVI because of the larger lesions associated with it.

“Another use for NDVI technology could be providing a whole-field view of any possible fertility issues that could be missed during scouting,” Kerns said. “If the issue is isolated then it could be possible to use a drone to help alleviate the issue.”

As with any research project in agriculture, some variables are beyond controlling for.

“Late-season disease development and small lesion size at first appearance led to some applications not being triggered,” Kerns said.