To paraphrase Bob Dylan mightily, you don’t need a weatherman to tell which way the wind blows, but some tape placed in trees can help you determine the speed at which you should drive your sprayer through an almond orchard.
University of California farm advisor Franz Niederholzer gave some advice in a blog posting on a simple way to evaluate sprayer air movement in the canopy tops of trees at different ground speeds.
His advice takes on particular importance as growers apply sprays during hull split in a year in which they face an especially tough battle with the Navel Orange Worm.
While the San Joaquin Valley has a particularly acute challenge in this fourth drought year with strings of hot days, growers whom Niederholzer advises in Colusa, Sutter and Yuba Counties are also seeing earlier pressures.
“The target is to get good coverage at the fastest speed at which you can do that,” Niederholzer said. “At petal fall earlier in the season, you can drive faster. There are fewer leaves. Now, at hull split, the leaves are out and the branches are bending with a big crop. Now is the time to be most careful because you have to spray through barriers.”
Working with UC horticulture intern Luke Milliron, Niederholzer came up with videos that show how surveyor’s tape can provide a good air movement indicator. Milliron shot two videos that display variability of efficiency in applications depending on the vigor and rootstocks. Another was shot by Stan Cutter, farm manager of Nickels Soil Lab in Arbuckle.
Niederholzer and Milliron credited Kim Blagborne, president and CEO of Slimline Manufacturing in Penticton, B.C., Canada, with coming up with the flagging to trace sprayer air movement.
The researchers say it basically works like this: Foot-long to 24-inch lengths of tape are tied to the top of a length of PVC pipe threaded through the branches in the middle of the tree row into tree tops. Or a pruning tower is used so that someone can get up in the tree tops and tie several lengths of tape onto the highest shoots.
Fill the sprayer half full of water, turn on the pump, close the spray booms and run the sprayer down the row at a set speed with the fan on at operating tractor RPMs.
Have someone record a video of the movement of the tape(s) in the three tops with a smart phone or iPad. Review the video after the spray moves past the pole or tape on branches.
Did the tape move at all? If not, then the sprayer air didn’t reach the tape, and neither will pesticide. The sprayer operator needs to drive slower, or you need a sprayer with a larger fan in that orchard.
Did the tape stand straight up? You might consider driving faster, as air moved past the tree tops at good speed, likely moving pesticide above the tree and creating spray drift.
If the length of tape just rustles at 45 to 90 degrees from vertical, you are probably getting the ground speed you want.
Niederholzer said coverage can be double-checked with the use of yellow paper cards from Syngenta that turn blue where water droplets touch the cards. Or droplets can be seen on Surround clay, a kaolin clay powder that is a form of whitewash that helps protect against sunburn. He refers to both products as “tracers.”
The videos that were shot were posted on YouTube. In all, they last under one minute.
They show a standard air blast PTO sprayer with a 36-inch axial fan. All sprayers travel at 3 miles per hour.
The first video shows sprayer output in a vigorous Nonpareil on Lovell rootstock at hull split. The lower branches thrash around and the iPad is buffeted, but at 20 feet up in the tree row, the flagging barely moves. The sprayer must slow down to provide better coverage, Niederholzer says. That video is at https://www.youtube.com/watch?v=d8ac7Bk1Ndw&feature=youtu.be.
The second video is in a low vigor Butte on Marianna plum rootstock on the same day as Video 1. The flagging at 20 feet off the ground is lifted almost vertically by air from the sprayer’s fan. Here, Niederholzer says, 3 miles per hour or faster should work to get pesticides into the tree tops. That video is at https://www.youtube.com/watch?v=gkpVFcHFHpo&feature=youtu.be
The third video was shot in a moderate vigor Nonpareil on Lovell planting at petal fall in late February. This speed looks to deliver good air movement in the tree tops of this orchard at that stage of development, Niederholzer says, adding that at hull split the sprayer is run at 2 miles per hour in the same orchard. That video is at https://www.youtube.com/watch?v=FzWOdG9cB7M&feature=youtu.be
“Speed doesn’t kill, but time is money,” Niederholzer said “Match the sprayer speed to the orchard and time of year for good spray coverage with the fastest ground speed, a combination that is vital to effective, efficient pest control.”