As the tree fruit industry continues to shift to high-density plantings, one of the biggest challenges has been making sure that the technology growers are using in the field matches their tree canopy designs and row spacings. Unfortunately, Matthew Grieshop, an assistant professor in Michigan State University (MSU)’s Organic Pest Management lab, says the current technology for applying pesticides has not adapted to what is happening in the orchard. In addition, the use of softer, reduced-risk materials means that efficiency is more important than ever.
It is for these reasons that Grieshop got involved in a collaborative research project that is based around a new spray delivery system. Using funding from a USDA Specialty Crop Research Initiative (SCRI) grant, the research team, which includes individuals from MSU, Cornell University, and Washington State University (WSU), is evaluating an application approach that’s been dubbed the “solid set canopy delivery system.” The system is based on a central pumping station that pushes material down the row through polyethylene tubing running at varying heights along the tree canopies, where it is then emitted via microsprinkler nozzles. If early results are any indication, the new system could present a wide range of benefits to growers, including bloom management, better coverage, and potentially much more.
Art Agnello, a Cornell entomologist who serves as the project leader in New York, first started evaluating this type of system 15 years ago at the New York State Agricultural Experiment Station in Geneva. Along with his colleague, Cornell Senior Extension Associate Andrew Landers, Agnello set up a fixed spraying system to measure efficiency at applying crop protection materials and controlling pests. While the scope of these early trials was small, the results showed insect and disease control that was at least equal to that of a conventional airblast sprayer. However, Agnello notes that “a number of engineering challenges were encountered that needed to be addressed to optimize performance and facilitate grower acceptance and implementation.”
In 2008, a core group of MSU researchers who had seen the project results presented at meetings opted to pull together a multi-disciplinary team and apply for a grant for funding. MSU entomologist David Epstein was the original leader of the project, and when he left the university to join USDA’s Office of Pest Management Policy, Grieshop stepped in. It took three attempts (as well as the incorporation of a team at Washington State University led by Jay Brunner, director of the Tree Fruit Research and Extension Center), but in 2011, $2.6 million in funding was secured through the SCRI grant, with an additional $2.8 million in matching funds provided from university and private sources.
Currently the teams from MSU, WSU, and Cornell comprise a wide range of specialties, from entomologists to ag engineers to plant pathologists to economists. John Nye of Trickl-eez Irrigation is also a member of the team, providing irrigation design expertise. “He has been a great resource, and he’s come up with most of the exciting ideas in terms of putting the system together,” says Grieshop. This will allow them to assess the system from a biological, technical, and economic standpoint.
According to Grieshop, the only complicating factor at this point is the lack of a long-term Farm Bill. “We have two years of funding right now and are waiting on another call for proposals,” he says. “It’s out of our hands right now.”
How It Works
According to Agnello, with the solid set canopy delivery system, pesticide sprays are applied through a system of microsprinkler nozzles attached to polyethylene tubing running along the tops of tree canopies and supplied by a central tank and pumping station. Spray nozzles supplied by tubing are attached to a support wire above the trees; single or double microsprayer nozzles are suspended on 8-inch or 28-inch lengths of tubing reservoirs alternating every 3 feet along the lateral tubing, and are fitted with anti-drip devices.
The reservoirs, which are in effect just sections of wider-diameter tubing, are large enough to hold a pre-determined amount of spray solution necessary to adequately wet the area of tree canopy beneath each nozzle. The spray solution is first pumped from a tank through an input manifold, and at a pressure sufficient for just filling all the tubing reservoirs without opening the nozzles; then, compressed air at a low pressure is used to push the excess liquid through return lines and back into the tank. Finally, compressed air at a higher pressure is used to open the check valves and spray out the liquid onto the trees. This leaves the system empty after the application, and ensures the recovery of unneeded spray solution.
Grieshop notes that with the reservoir approach, “we’re hoping to charge the system and use air instead of water as a carrier to decrease leftover material at the end. Down the road, as we get away from pre-mixed solutions we pump out and toward a direct injection system, that will also help with efficiency.” Agnello echoes Grieshop in this area. “We were able to determine that, without the use of a reservoir system in the microsprayer assemblies, about three times as much water would have been needed to fill and spray out the tubing used in these tests. The reservoir design can affect a considerable time reduction in spray operation.”
Bloom Delay, And More
The benefit of working across different regions, says Grieshop, is that “because we are so focused on different problems, sometimes the solutions we come up with for an unrelated problem can help another region.” For example, perhaps the most significant advantage the solid set system might bring for growers in Michigan is bloom delay through manipulation of orchard microclimate. “In Washington, they looked at sunburn damage, which is a big problem for them. The evaporative cooling they use for sunburn is what we can use to delay bloom.“
Based on the data they’ve seen so far, Grieshop thinks they can delay bloom by seven to ten days, which can make all the difference in the world in a year like growers experienced in 2012. “Delaying bloom is a risk-avoidance way to protect ourselves. If we delayed bloom for three days here in Michigan this past year, we would have had at least 50% of our crop, as opposed to losing 80%. It’s a matter of a few hours.”
Delaying bloom has another advantage. “From a marketing standpoint, if you can delay bloom in some of your blocks and not others, you might be able to stretch harvest for some varieties,” says Grieshop. “That could be great for sweet cherries since they don’t keep as long.”
Of course, efficient pest management is the ultimate goal of the project. Grieshop notes that for so long, the limiting factor in pest control has been that there is not enough equipment to cover enough acres in a timely manner. “If we can change the system so it takes 10 minutes to apply on 1 acre, you could make applications every three days, and put on a lighter coat with better coverage and less active ingredient. This helps the grower’s bottom line, and is also environmentally friendly because there should be less runoff. There’s also the issue of maximum residue levels to consider. “The less material you put out, the less it shows up as residue,” says Grieshop. “That’s important for growers in international markets.”
Out in Washington, Brunner says the system could be a potential replacement for tractor-drawn airblast applications for insect and disease control, crop load management, and sunburn protection. “Because pesticide applications could be applied quickly, it would be possible to use conventional pesticides at reduced rates, or soft pesticides with short residual life, like codling moth virus, more frequently and still achieve acceptable pest control,” says Brunner. “In other words, an effective system could revolutionize how pest control is implemented in tree fruit orchards.”
Aside from pest control, trials in Michigan and elsewhere are also weighing the issue of wind versus dead air, as well as the placement and configuration of nozzles and how they affect deposition. In cherry trials in Michigan, which are taking place under tunnels, the dead air led to good coverage on the tops of leaves, but poor coverage below. Grieshop notes that a light breeze may actually help pick up particles and cycle them through the air. “We need to think about the optimal range of wind speed, and how to account for that,” he says.
In terms of nozzle placement, it seems like both vertical and horizontal orientations may be necessary. In the Michigan trials, MSU entomologist John Wise has used dyes and water sensitive paper to determine percent coverage on the target area. “We need to think about how to tweak the system for 2013 to take advantage of what we have learned and counteract any susceptibility to drift,” says Wise.
Next Steps Critical
It is important to note that this project is only in its early stages, and it will take more work before the system is widely accepted (see “When Can You Use It?” sidebar). In Washington, Brunner’s team will be looking more at crop load management incorporating bloom and post-bloom chemicals delivered through the solid set system and by airblast sprayer. “We will continue to work with the engineering group to identify different emitters to incorporate into the system and evaluate the coverage provided by the different emitters using dyes, water sensitive cards, and bioassays.”
Grieshop says they also need to demonstrate to the irrigation industry that there is a huge potential market, and they will need to engineer products specialized for these purposes. One simple modification he notes are a couple of plastic arms that hook up over the top of the pipe and hold it in place. “If you need 1,000 emitters per acre, that means you have a million units per 1,000 acres that someone could be manufacturing,” he says. “If we can show it works and where we need better engineering, the industry will do it. It seems like a no-brainer for them.”
Grieshop is optimistic about refunding the project. “I’ve been impressed with the work we’ve gotten done in the first year. We produced more data than I thought we would, especially given the weather of this past year.”
The MSU team is putting together a news report available on their web site (canopydelivery.msu.edu). They’ve also been posting summaries of field days and some research reports. “I am impressed with how well we’ve produced. Having the teams in different states has helped us learn from our mistakes, and figure out how to fix them.”
When Can You Use It?
So how close is the solid set canopy delivery system to being used on a commercial basis? It depends on who you ask. Grieshop notes that early adopters will be key. “We are already working with some growers putting this into small plantings, one- to six-acre blocks, to try it out. For this to be widely adopted, I’m thinking a decade.”
Brunner says some growers could implement the system immediately. However, “the solid set canopy delivery system remains a concept in need of optimization. We have identified some major limitations using current off-the-shelf technologies, mainly dealing with coverage of foliage and fruit surfaces. We also do not have a good handle on the potential economic cost, and there remain questions about the long-term reliability of such a system.”
Perhaps Agnello sums it up best when he says there is a difference between getting the system operational and making it practical and economical. “We recognize that, in its current form, this system is not yet optimized for large-scale adoption by most commercial growers, although having a few industry leaders involved and committed to working with us on this will certainly facilitate the process,” he says.
“I would think that we could have a fairly reasonable set of recommendations for commercial growers who might wish to try this approach on their own after the third year of our work (2012 was Year 1). By the completion of the project, we should have a very realistic grasp of the costs, strengths, weaknesses, and overall time/labor requirements of implementing it on a commercial scale.”