Timothy J. Smith
There are very few new methods of application that a tree fruit grower must learn in a lifetime. One new method of application has come along with a relatively new material adopted by both conventional and organic cherry growers in Washington State.
This new material is a bait that must be slightly diluted, then lightly spattered on the tree, very unlike other control materials, which are applied in 80 to 400 gallons of water per acre. The bait speckles are discovered by the ever-foraging cherry fruit flies as they move about the trees each day, and, when they feed, the very small amount of organically-accepted active ingredient (spinosad, 0.01%) controls them. This approach has been rapidly accepted, but many growers are asking how to build a sprayer and apply the bait. Both operations are less complex than most of the mechanical work and application growers frequently do. Below is my first effort to describe the bait sprayer and how to use it:
Construction of the Bait Applicator:
(Click on underlined words for a picture)
If you don’t want to do this, the ready-made versions are for sale from various local sources.
First, gather all your parts:
An auxiliary sprayer with 12 volt pump, either 45 or 60 pounds per square inch will work, usually about 12 to 15 gallon capacity.
Nozzle and boom parts. Actually, there are many ways to configure this boom. The important factors you must include are the ability to change the angle of the spray stream so you can adjust to different tree sizes and row widths, the ability to use a Disc style nozzle tip (D2, D1.5 or D1) and a valve to allow either side to be turned off while you cover the outside row. The example will use two adjustable angle single swivel nozzle bodies. I wish now I had used one double swivel nozzle body, as it is not important to separate the nozzles on the boom. The bait mixture stream shoots 15 – 22 feet, starting near the middle of the drive row just does not matter.
You will also need a heavy duty 12 volt switch you can attach on your ATV handle bar, so you can turn off the sprayer while turning at row ends, etc., and some wire to splice into the switch wire on the sprayer, and whatever clips you think you’ll need to securely connect the sprayer’s power lead to your ATV battery. Oh yeah, and an ATV. If you don’t have one, you now have a reason to get one. It is impossible to apply this product properly with the standard air-blast sprayer. An ATV is far less expensive to run, and easier to get into the orchard after the fruit pulls the limbs down.
Build Away…… Ours looked like this because we wanted it to be extra portable, so we could run tests at various orchards quickly. We later lowered the boom to get it out of the way a bit more. You probably can do without the PVC pipe cage. Clamp your boom onto your ATV any way you wish. Don’t scratch the new paint…….. Putting the nozzles on the front of your ATV will make them easy to watch while you spray, but you’ll get speckled with the sticky bait.
There is a certain amount of trial and error that you must go through before you get the rate just right. The following tips will get your rate per acre very close to the require 20 ounces. You can adjust the nozzle tip size, the dilution somewhat, or your speed to get it correct on subsequent applications. I suggest you do 2 – 4 acres at first to check your application rate.
MIX THE PRODUCT OUTSIDE OF THE SPRAYER, OR ELSE! This bait is a thick, sticky substance, and will remain in a “blob” at the bottom of your tank if added directly without mixing. Most report a 5 gallon pail and a paint mixer attachment on an electric drill simplifies mixing. Warm water works much better than cold..
The per acre rate of product is 20 ounces. As it is a bait, it must dry to little “bait stations” on the foliage to be effective, so you must avoid over-dilution with water. The dilutions that have been reported effective on other fruit fly pests range from 1 part bait to 2 parts water (1:2), up to 1 part bait to 5 parts water (1:5). I did my research on cherry fruit fly at 1 part bait to 3 parts water, and have applied most of the ATV treatments at 1:4, mainly to allow for slower application speeds. The rate of dilution will make quite a difference in flow rates out of the small nozzles you will be using. Stay consistent once you get the calibration worked out.
So, at 1:4, I used a D2 disc nozzle, and mixed 20 ounces of bait to 80 ounces of water for each acre with 20 foot row spacing to be sprayed at about 6.2 MPH on every other row middle. This 1:4 dilution allows you to drive a reasonable speed with the D2 nozzle. You must count on an extra 50 ounces of mix that will remain in the tank when the pump begins to suck air. If you keep this mix, it will ferment unless refrigerated.
With a D1.5 disc nozzle, I mixed 20 ounces of bait to 60 ounces of water for each acre with 20 foot row spacing to be sprayed at about 6.8 MPH. This allowed us to apply the product at 1:3 dilution, perhaps a “better” dilution rate. You will also be able to cover more acres with one tank load. It is a bit difficult to find the D1.5 nozzle size, so you may have to special order them. I believe there are advantages with this nozzle tip size.
Aim the nozzles so the stream hits the bulk of the tree in young plantings (smaller trees) or the upper 1/3 of larger trees. The CFF will find the bait if it hits the foliage or fruit, but they may do so sooner if the bait is in the upper 1/2 of large trees.
With the D2 nozzles, and 20 foot wide rows, and 1:4 bait dilution, the rate per acre came out just right when the applicator drove at 6.2 MPH on EVERY OTHER row. Alternate row spraying is fine, as the spray seems to penetrate to both sides of the tree. You may want to wear a helmet to protect your eyes and noggin.
With the D1 nozzles, we could drive much slower in low hanging limbs, but this nozzle tip seems a bit small to apply the proper speckles of bait. At the 1:4 dilution, and at 20 foot spacings, we could spray every other row at 3.7 MPH.
The suppliers often will have helpful hand-outs to guide you for other dilutions and row spacings.
NOTE! CLEAN AND FLUSH THE SPRAYER AFTER USE! The bait will glue the parts of the pump together, and the next time you want to use it, it won’t work.
Question: How do I determine the speed of an ATV without a speedometer?
Answer: People tell me that they use GPS devices to calibrate speed, if they have them. I guess you can get a MPH read-out on the GPS unit. Then you note the rpm and gear that gets you in the neighborhood of the correct speed.
You can also time yourself over a distance. At 6 mph, it should take about 10 seconds to drive 88 feet. 8.5 seconds/88 feet is 7 mph. So, this is part of the “trial-and-error” phase of getting it right. Take a few runs with the ATV at certain gear, rpm settings. Get a “running start at the course, and use a course longer than 88 feet to be certain that you get an accurate timing. Example:If your trees are planted on 20 foot in- row spacing, keep track of the time it takes to cross 9 tree spaces (180 feet). If your ATV is traveling at 6 mph, this will take about 20 seconds. At 7 mph, this will take 17 seconds.
6 – 7 mph is the speed suggestion for the D2 nozzle tip, 20 foot row spacing, and 20 oz. bait to 80 ounces of water per acre. If your rows are different spacing, (18?), you use the D1.5 nozzle tip I am now going to recommend, and you mix the bait at 20 ounces bait to 60 or 70 ounces of water, all of this calibration will be somewhat changed. This is why you have to adjust this by the “trial and error” technique the first time you apply it. You will be high or low on the first load. Speed up or slow down slightly to adjust the rate. Keep the bait mix at 20 ounces of product per acre, no less than 60 ounces water per acre, no more than 80.