Perimeter Spraying For Grape Berry Moth Can Cut Costs

A team of researchers is working to develop cost-effective spray equipment that allows growers to spray vineyard edges for better control of grape berry moth.

A team of researchers is working to develop cost-effective spray equipment that allows growers to spray vineyard edges for better control of grape berry moth.

New research offers some insight into the most effective methods for combating grape berry moth, and the equipment necessary for grape growers to employ these methods in the vineyard.

The Grape Berry Moth Precision Application of Reduced Risk Insecticides project looked at various spray methods and found precision spraying works just as well as full cover sprays to control grape berry moth.

Advertisement

Grape berry moth tends to be more prevalent in vineyards situated next to woodland areas, and research conducted as part of the project in 2014 found border areas of vineyards suffered significantly more damage from grape berry moth (up to 70% damaged clusters) compared to just 10% to 20% damaged clusters in interior areas.

Rufus Isaacs and Keith Mason in the Michigan State University Department of Entomology found mid-season precision spraying around the edge of vineyards using a higher low-risk insecticide rate offered better control compared to standard full cover applications.

Top Articles
Have a Plan For Climate Change? Why Fruit Growers Need To Act Now

In addition, applying insecticides only at the border of the vineyard can reduce chemical input expenses to as little as 20% to 30% of the cost of a full cover application. By applying the insecticide during a scheduled fungicide application, the cost of the precision insecticide application would be minimal.

There are environmental benefits, too, because growers can target insecticides only where they’re needed. “This should result in a great potential for biological control agents to persist within the field, allowing for a more stable low pest population in the vineyards [and] orchards,” Isaacs says.

Equipment Considerations
In 2013, Mark Ledebuhr of Application Insight LLC joined the research team to find equipment solutions to make these types of precision applications possible for grape growers as part of other scheduled fungicide applications.

“Single Chemical Injection (SCI), or the ability to apply a single chemical selectively on an as-needed basis, is a mature technology in grains spraying, but adapting it to horticulture has some distinct challenges,” Ledebuhr says.

Scale is just one of the challenges. Because the boom swath is wide and speeds are fast in grains, the flows needed to apply undiluted products are relatively easy to produce and manipulate, he explains.

“In the applications we are looking at, the swaths are narrow and the speeds are slow, so when we’d like to apply, for example, 12 ounces to the acre of injected insecticide, that works out to a fraction of an ounce of undiluted product per minute. Injecting these very low flows uniformly is difficult; it falls below the flow ranges of the injection pumps.”

Ledebuhr and others working on the project came up with prototype systems for this kind of application, but they found they still had to dilute the products with water to get suitable flow rates.

“A system capable of undiluted flows in typical grape application conditions would just be too delicate and unreliable,” he notes. “Also, once diluted, some formulations can fall out of suspension and require constant agitation.” Commercially available equipment does not provide for this agitation.

Another challenge is pressure, Ledebuhr says. Commercial injection systems are limited to just 150 PSI, but horticulture sprayers often use high pressure, centrifugal, piston pumps that operate from at least 200 PSI. “Attempting to inject against those would render the injection system useless,” he says.

To address this problem, the researchers created a system that applied the SCI flow through a separate spray boom not connected to the main system. It instead sprays into the main spray stream and is mixed there, which proved effective.

Another challenge is latency – the time between when you inject and when the material actually comes out of the nozzle.
Boom valves in grain sprayers are usually right on the boom, which minimizes latency.

“Ideally, a properly installed SCI injects just above the boom valves,” Ledebuhr says. “The computer-controlled injector can then easily adjust the injected amount based on system flow rate and on how many valves are open with little extra hardware.”

The boom valves in a typical vineyard sprayer, on the other hand, are usually as far away from the nozzles as possible, which helps limit overspray exposure.

“This is a problem for injecting due to the volume of spray in the connecting hose,” Ledebuhr explains. “Depending on the sprayer design, travel time from the injection point at the boom valves to the spray manifolds can delay the spraying of the injected chemical eight to 12 seconds or more.”

A speed of 4 mph is 6 feet per second, he adds. At typical travel speeds, the chemical may not be released from the sprayer for 72 feet or even more. “When you only want to spray the first 150 feet of the row, that kind of lag just doesn’t work,” Ledebuhr says.

To overcome this problem, the team designed a system that has injection points on the spray manifold, which provides latency of less than one second. Another MSU-designed system, with a parallel spray boom, has no latency at all.

Economics and demographics present another challenge, Ledebuhr says. In the Great Lakes region, few juice grape growers use rate controllers. That means if growers wanted to employ perimeter spraying using a commercially available SCI, they’d have to buy a rate controller and all the associated control hardware as well.

“The install can be complicated due to the small footprint typical of these kinds of sprayers,” Ledebuhr says. “There’s just not a lot of real estate to work with, so for an install, a grower will need a competent serviceperson or be willing to make fairly extensive modifications themselves to the sprayer.”

These costs can add up fast, and there’s a learning curve, too.

“Rate controllers make spraying easier, but they also make the sprayer a more complex machine,” Ledebuhr notes.

Taking all of these challenges into consideration, the team has been working to develop relatively low-tech, stand-alone injection systems, Ledebuhr says. These systems would provide many of the benefits of a “true variable rate SCI system,” and also solve the problems outlined above.

“We’ve worked to keep it simple enough that the average grower can implement, use, and maintain one,” he adds. “We now have created prototypes that are capable of working effectively and easily in juice grapes with most types of sprayers. These same systems should translate easily into winegrapes and other woody crops.”

Commercial Availability
As for the future commercial availability of the prototypes, many growers have said they’d be interested in building the equipment from kits with instructions, which would be a more affordable option than purchasing a complete piece of equipment.

“This would change the economics to where there would likely be less of a cost gap between a currently commercially available SCI and what the MSU systems would likely retail for as a short-run specialty product,” Ledebuhr says. “Based on this, we’re re-evaluating the path forward a bit.”

Currently, the team is looking at different commercialization options and also reevaluating strategies for overcoming some of the challenges of implementing the currently available SCI units in grapes.

“The bottom line is that we want to figure out as many ways as possible to help growers succeed with precision perimeter spraying,” he says.

0