While the California almond industry pursues various ways to reduce the dust associated with the crop, a group of engineers at the University of California, Davis is testing equipment designed to monitor the amount of particulate matter released during harvesting.
One of them, Ken Giles, a professor in the biological and agricultural engineering unit, recently described the experimental device during a regional almond day program at Coalinga. Basically a sensor originally designed to measure power plant smokestack emissions and attached to an almond harvester, the unit uses a pulsing light beam directed across air-flow tubes as the nuts are picked up.
It indicates the amount of dust interrupting the light, and the data is saved in a computer. Termed an "in-line sensor," it serves the same purpose as equipment used to measure emissions from motor vehicles.
"There is information that says harvesting is one of the most dust-intensive operations," Giles said. "One of the problems in monitoring air quality is it is very, very time consuming with setting up and weighing filters placed around a field. It can take years to collect data.
"Our purpose is to provide something more practical and efficient for growers and to help machinery manufacturers develop new machinery. Growers know there’s dust out there, but we are beginning to get some numbers to apply to it."
He went on to say they looked for something "off the shelf," a commercially available sensor, without having to "re-invent the wheel" from scratch. Collaborating with Flory Industries, the UCD team attached the sensor to a Flory 850 PTO nut pick up machine and tractor and fitted a computer to collect data. Part of the challenge, Giles said, was adapting a device designed for stationary use to a mobile application.
Variables affect dust
In limited trials last year, the equipment showed that several variables in harvesting operations, including ground speed, machine adjustment, soil type, and yield intensity, affect the amount of dust generated. This coming season they plan to continue collecting data with a separate, trailer-mounted device operated near the pick up machine.
"It may be that in some parts of an orchard, reducing speed might have a big effect on reducing the amount of dust generation," he noted, adding that, on the other hand, reducing speed and prolonging the operating time may cancel out that benefit. "We are looking for some balance between them."
He said this year they plan to investigate windrow preparation, the amount of spider mites and leaves present, and perhaps nighttime operations, while they collaborate with other scientists observing irrigation practices and use of polyacrylamide compounds to reduce dust.
Support for the project has come from the Almond Board of California and USDA.
Another speaker, Rich Coviello, Fresno County farm advisor, told the group the almond industry’s problems, particularly at hull split, with its premier pest, navel orangeworm, are greater than they were when he took his post 37 years ago. And although the insect hasn’t changed a bit, the industry, and host crops grown around almonds, are significantly different and the NOW problem has become area wide, not confined to individual ranches.
"Some 30 years ago, a large almond acreage was 300 to 400 acres, and the average was about 150. We started working with the winter sanitation program and it was quite successful in orchards of that size," he said.
Today, in contrast, some almond ranches have expanded to thousands of acres, making spray applications and other practices more difficult to accomplish in a timely manner.
The management strategies and cultural techniques based on removing all the mummified nuts from trees and destroying them, he said, were sound then and remain so now in interrupting the NOW’s breeding cycle.
"Winter sanitation eliminates hosts for NOW for two generations, the overwintering brood and the first generation in the spring, and you can’t spend money much better than that."
But changes in cropping on Fresno County’s west side have given NOW new havens outside the almond orchards. Examples of other expanding acreage of hosts are pomegranates, pistachios, walnuts, citrus, and prunes that also have to be purged of NOW infested mummies. "Remember, in dealing with NOW, it’s a numbers game. The more of them you get rid of, the fewer problems you have," he said.
If a good job of winter sanitation has been done, there will likely be no need for a May spray, but if the sanitation is not complete, the May spray, when populations are smaller and more synchronized, Coviello said, may be more effective than a spray at hull split.
Early harvest of almonds, or, in most years, having them on the ground prior to the third generation of NOW during late July or the first week in August, is another practice that also remains sound. "If you get those nuts on the ground before that generation starts, you can reduce damage. We know from previous research that damage can increase one-half of one percent each day after the start of the third generation," he said.
The combination of winter sanitation and early harvest can confine NOW damage to 2 to 3 percent where it would otherwise be 10 to 20 percent.
Turning to the issue of shell seal and its relation to NOW, Coviello said a lot of the pollinator varieties that have tight shells do not become as infested with the pest compared to Nonpareils. Research suggests that avoiding large applications of fertilizers and using smaller doses with more frequent irrigation can help promote smaller nuts with tighter shell seals to discourage infestations.
Larger nuts tend to have more open shell seals, and, given this spring’s wet weather and poor pollination, the lighter almond crop suggests larger nuts, which will likely have more open shells, and greater pressure for NOW infestation this year.
Another way to manage NOW is ensuring more thorough coverage of chemicals. Older compounds were more forgiving because of their fuming action, but newer products are more selective and require precise placement.
Although the adoption of greater tree densities, he said, has many other virtues, it favors NOW. Standard spacing allows better penetration for both sunlight and sprays, while close spacing, especially when trees are not topped, promotes shading and a later and more prolonged hull split, making timely sprays more difficult and the nuts more vulnerable to NOW.