Healthy buds mean healthy flowers mean healthy fruits. And using sprayers to protect all those parts of the lifecycle is important, but how do you know which sprayer works best for your operation?

“Comparing efficiencies of spray technologies in tree fruit orchards” was presented by the team of Emily Lavely, Michael Reinke, Erin Lauwers and Lindsay Brown of Michigan State Extension at the most recent Great Lakes Expo.

The team said, “Understanding canopy coverage of various spraying technologies is critical to the success of the tree fruit industry as production costs continue to rise and market prices for fruit remain low.”

Their project built on previous work done to increase the understanding of the utility of unmanned aerial vehicles (UAVs, or drones) and the next generation sprayer technologies in Michigan orchard systems. They directly compared the spray coverage of four commercial sprayers to give growers a better understanding of how these technologies could be utilized on their farms.

Their testing looked at the percentage of spray coverage in high-density apple, young sweet cherry and established pear orchards at the West Michigan Research & Extension Center in Hart, MI, in late September 2024. (These orchard trials are being replicated this year, as will a trial in a mature tart cherry orchard.)

Taken into consideration were spray coverage, application time and water usage of four commercial sprayers: the Pul-Blast sprayer (a standard air blast treatment); the Nelson Hardie sprayer with a Smart Apply® Intelligent Spray Control System; the Pul-Blast sprayer with GVF Sonic Spray; and a drone (the DJI Agras T40).

Water-sensitive spray cards were positioned high, middle and low on fiberglass poles throughout the orchard canopies. These spray cards were assessed with ImageJ software to measure droplet coverage.

What is considered “good” spray coverage? More coverage is not always better. Research has shown that water dripping begins when spray coverage is above 75%. That dripping may reduce efficacy and increase the off-target movement of pesticides.

An adequate pesticide application in fruit crops normally requires about 10% to 15% coverage. Above this level, there are enough point sources of the product to protect the crop from the targeted insect or disease (in most cases).

This experiment found the air blast and sonic spray treatments provided the most coverage – sometimes close to 100% – but also the most drift (near 40% in both instances).

The research conclusions were as follows:

Air blast: Over-coverage on the spray row

Sonic Spray: Adequate coverage with instances of over-coverage

Smart Apply: Reached minimum adequate coverage

Drone: Poor coverage due to distance from young trees to avoid trellises and inadequate compensation for crosswinds

All four of the options tested had some coverage above the 15% threshold. While some growers use the targeted drift technique to save time and inputs, it does reduce application efficacy and increases drift out of the orchard.

As a reminder, growers should consider tractor speed, nozzle type, disc core type, nozzle position and pesticide coverage needs when evaluating their own canopy coverage. These factors were not standardized across sprayer types in this trial and equipment applicator settings were used for each sprayer type. The researchers noted that future evaluations will consider standardizing these factors which may impact water use, canopy coverage and droplet size.