When it comes to making the most effective, most efficient and most environmentally friendly use of the latest chemical tools available for controlling diseases and insect pests in orchards, it may be time for California tree nut producers to re-think the way they manage their sprays, says Franz Niederholzer, University of California Cooperative Extension orchard systems farm advisor for Sutter and Yuba counties.
That may mean adopting new technology.
“The game is changing and tree nut growers may find value in the way other growers are improving their spray management techniques,” he says. “Some of the most intriguing technological developments are occurring in highly managed tree systems, like the dwarf apple orchards in the Pacific Northwest.
While some of these advances may not apply directly to tree nut orchards, they might point the way to developing better equipment and practices for managing sprays when treating almond and walnut trees, Niederholzer notes.
Among the possibilities:
Canopy sensing spray systems — Available for about the past 15 years or longer, this technology uses ultrasonic sensors that turn on all or some of a bank of nozzles when they detect a tree canopy as the sprayer moves through the orchard and off again once they pass the tree.
These systems, which attach to standard air blast sprayers, are very effective in young orchards and in older blocks with a number of younger, replanted trees, Niederholzer says.
However, the electronics have a higher maintenance requirement.
“Some growers say their smart sprayers can save them 25 percent of their chemical costs,” he says. “But, they are willing to do the extra maintenance these systems need. Others who have bought them wish that they hadn’t. Acceptance of this equipment often depends on how a farm is operated. Owner operators love them, but big operations with hired labor often don’t have good success with this technology.”
Tree sensor spray systems — This technology operates on the general principle of a smart spray system, but sells for about one-third the price. Used almost exclusively in young orchards, it reduces chemical costs by controlling the spray when it detecting the presence or absence of a tree. The units turn on/off one side of the sprayer only, and have their best fit in an orchard with uniformly-sized trees.
Tower sprayer — A conventional air blast sprayer sprays a mixture of air, water and chemicals up through the tree canopy. The spray may end up 10 feet to 30 feet above the canopy, where as much as 10 percent of the chemicals can be lost in the wind. A tower sprayer, on the other hand, blows the spray horizontally and can produce a uniform curtain of spray from the bottom to the top of the tree, and reduces drift.
Using this technology with almond or walnut trees would require the use of a mechanical hedger/topper unit to create a slot, about 6 feet wide, through the tree branches above the row middles, to allow passage of the tower and to provide adequate spray coverage, Niederholzer says.
Electronic flow control — Popular in tower and conventional air blast sprayers used in the Pacific Northwest, these units electronically adjust the flow of chemicals as ground speed of the spray rig changes to maintain the desired application rate.
“This works nicely in the dwarf apply orchards and would also work with tree nut crops,” Niederholzer says. “You know exactly how much chemical you’re putting out so that you’re not over- or under-spraying. This saves money in chemicals or poor pest control.”
Venturi or air induction nozzles — Replacing existing nozzles on conventional hydraulic air blast sprayers, these nozzles are designed to produce bigger drops that don’t drift as far.
They produce a little more spotty coverage than conventional nozzles and may require a little more spray volume to give uniform coverage, Niederholzer says.
“The jury’s still out on the value of venturi nozzles in orchard crop spraying in California,” he says. “Some growers report they work fine; others say these nozzles don’t work as well.”