Occasionally it becomes necessary to apply fungicides to an area too small for treatment with a tractor-mounted sprayer. Below, I share my thoughts on examples of equipment that might be used to treat small areas.
Let’s consider an example where one wants to apply a fungicide for management of Botrytis gray mold on tomatoes in a greenhouse. First, make sure that the product is labeled for tomatoes, gray mold and the greenhouse. (Some labels have statements that prohibit pesticide applications in a greenhouse. In other cases, the label is silent on the matter of greenhouse applications. In the latter case, greenhouse applications may be made-with care! See page 40 of the 2014 version of the Midwest Vegetable Production Guide for Commercial Growers <mwveguide.org> for more information. ) Make sure to read all the label statements for precautions such as worker protection clothing, Re-Entry Interval (REI) and Pre-Harvest Interval (PHI). What type of sprayer should one use? Let’s review a few different types of sprayers.1. The hand sprayer-This is the type of sprayer that one would buy at the local garden center or hardware store (Figure 1). Most have a capacity of 1-2 gallons. I like the hand sprayers that have a quick release valve on the side. After the application is complete, this valve can be used to release pressure prior to opening up the tank. The release of pressure makes it less likely that pesticide will escape out of the tank when the pump handle is unscrewed.
Figure 1: The common hand sprayer may be
purchased at the local hardware or
garden store. Note that this one has
a quick release valve.This type of hand sprayer is readily available, inexpensive and easy to use. However, using a hand sprayer to apply fungicide to a row of tomatoes, for example, can be difficult. Applications with a hand sprayer are often made with an up and down motion while moving down the row of plants. It can be difficult to apply the same amount of spray to every plant in this fashion. In addition, the nozzle of most hand sprayers is adjustable from a thin stream to a wide spray. The wide spray is more useful to fungicide applications; however adjustment of the nozzle may be inadvertently altered, thus changing how the spray is applied. 2. Backpack sprayers may be ordered through catalogues or on-line (Figure 2). Many backpack sprayers may be pumped up by hand while applications are being made. Sprayers with a pressure gauge on the handle make it easier to apply fungicide with a consistent pressure/amount to each plant. Some backpack sprayers have a flat fan or hollow cone nozzle. These types of nozzles are made for fungicide/pesticide applications, unlike the adjustable nozzles described above which are multi-purpose (Figure 3).
Figure 2: This backpack sprayer has a pressure
gauge on the wand and a separate
pump handle so that pressure can be
maintained while spraying.
Figure 3: The top nozzle is a flat fan nozzle
designed for pesticide applications.
The bottom multi-purpose nozzle
may be adjusted from a thin stream
to a wide spray and may be changed
inadvertently during a pesticide application.
3. CO2 sprayers can be purchased that are worn as a backpack (Figure 4). Instead of pumping up these sprayers by hand, a CO2 cylinder is used to propel the spray. This allows for a more consistent spray. Typically, these sprayers utilize a boom sprayer with hollow cone or flat fan nozzles. Using a boom with 3 or 4 hollow cone or flat fan nozzles makes it much easier to apply fungicide consistently to a large section of plants compared to applying the same product with a wand.
Figure 4: Here the use of a backpack
CO2 sprayer is demonstrated.
Advantages of this sprayer are
the CO2 propellant that allows
a consistent spray and a boom
of 4 nozzles that makes applications
easier and more effective.
4. Growers may want to devise a system of their own. Here I describe a piece of equipment that Dennis Nowaskie, superintendent of the Southwest Purdue Agricultural Center, created to apply fungicides to tomatoes in our high tunnels (Figure 5). The sprayer consists of a tank and pump which was manufactured to be used on the back of an ATV. The tank is mounted to a flat piece of aluminum which is mounted on wheels so that the entire unit may be pulled-sort of like a wagon. The pump is powered by a 12 volt battery which has a small trickle charger attached in order to charge the battery when not in use. Two booms are attached vertically on either side of the pump. Either boom or individual nozzles can be turned on and off to spray the crop on either side or any height. Either boom can be lowered so that crops close to the greenhouse wall can be sprayed. The sprayer is pulled at a consistent speed between the rows.
Figure 5: This greenhouse sprayer,
designed by Dennis Nowaskie
at the Southwest Purdue Ag Center,
can be pulled between the rows of
tomatoes. Each nozzle may be
turned off and on and both booms
can be lowered if necessary.
This sprayer is an example of the
type of equipment that can be
fabricated to apply fungicides to
a small area.
Choosing the right piece of equipment is just a part of the battle. Next, the sprayer needs to be calibrated. While most growers understand how to calibrate a tractor mounted sprayer, it may not be obvious how to calibrate a sprayer that is powered by a human. In my next blog, I will describe one way in which hand sprayers of the sort described here can be calibrated to deliver the right amount of fungicide to the plant.