How do you know how much product you are putting out if you haven't calibrated your sprayer??

At the recent ARS field days in Froid and here in Sidney, I did a session on calibrating spraying equipment.  While there has already been a good portion of pesticides applied in the county, a little reminder about applying the right amounts never hurts. 

It used to be that calibrating a sprayer was a long, difficult, drawn out process that seemed like a person needed a degree in mathematics to do, but that is not the case anymore.  Now, calibration of both boom sprayers and hand-held sprayers can be done easily with very little math involved.  When applying pesticides, whether it be with a large boom sprayer or a hand-held sprayer, it is important to know how much product (in gallons per acre) is being applied.  Here is how to do that.

With a boom sprayer, this is done in 4 easy steps; 

 1.       Determine the length of the course that you need to drive.  This is done by dividing 340 by the nozzle spacing (in feet) of your boom.  For example, if the nozzles on your boom are 18 inches apart, the equation would be 340÷1.5 which equals 227.  So your course would be 227 feet.

2.       Time how long it takes you to drive the course at a constant spray speed.  You should make sure you are up to speed prior to starting the course and should travel it 2-3 times and take an average.

3.       Collect liquid from a nozzle at a constant RPM/pressure for the amount of time found in step 2.  Prior to doing this, you should make sure that your nozzles are putting out the same amount of product by averaging all nozzles on the boom and either cleaning or replacing those that are putting out product at 10% above or below the average.

4.       Determine Gallons Per Acre (GPA) by converting ounces of liquid obtained in step 3 into GPA.  If 20 ounces where obtained then you would be putting out 20 GPA.

For handheld or backpack sprayers, the process is essentially the same, just done on a smaller scale.

1.       Measure an area 18.5’ by 18.5’.  This represents 128^th of an acre.

2.       Time how long it takes you to walk and spray (at as much of a constant pressure as you can) the 18.5’ by 18.5’ course.  Just like with the boom sprayer, you will want to do this a couple of times to determine an average.

3.       Spray liquid (water) into a measuring container for the length of time determined in step 2.  Again, you will want to try as best as you can to maintain a constant pressure.


4.       Determine GPA by converting the ounces collected in step 3 directly to GPA.
Now this may appear to be time consuming but it really does not take too long and may help in the long run financially as you may not need to add as much product as you thought.
I would suggest visiting http://msuextension.org/publications/AgandNaturalResources/MT200915AG.pdf for more information about calibrating different types of sprayers and determining nozzles.  I also have a couple of digital readers that I am happy to let you borrow that will tell you how many gallons per minute your sprayer is putting out and makes it a little easier to get a good recording.

Wet conditions are favorable for disease development.

 

In case you have never seen the image above, it is called the disease triangle.  Like any triangle if one of the points does not exist, the triangle does not exist.  Typically, in Eastern Montana, we may have the host and pathogen present in our crop fields but because we do not normally receive much in the amount of rainfall and therefore, our crops do not remain constantly wet, we do not have the correct environment for most diseases to get established.

Well, this year we have had a wetter than normal spring and, because of this, I have received a few calls regarding patches of diseased winter wheat stands.  Here is an article from the recent issue of the NDSU Crop and Pest Report.

Tan Spot (06/06/13)

Tan spot is beginning to be found in several areas of the state. Growing degree accumulations across the state indicate that wheat fields planted from May 1 to May 10 are in the 3 to 5 leaf stage now. 

 

Tan spot is the common fungal disease caused by Pyrenophora tritici-repentis, which infects winter wheat and spring wheat regularly in all the counties of North Dakota. The greatest likelihood of a yield loss to tan spot occurs when spring rains favor disease development with temperatures above 10°C (50°F), a susceptible or moderately susceptible variety is planted, and when the crop is planted into wheat residue.
Tan spot showed up in winter wheat fields in regular weekly scouting in some counties of ND (McHenry and Ward) already.
The early infections are small tan to brown spots surrounded by yellow halos often referred to as lens shaped lesions (Figure 1). These lesions coalesce into large blotches as they age, resulting in a premature senescence. The tan spot pathogen commonly infects leaves (Figure 1) and stems (Figure 2) contributing to severe yield losses.
There is an excellent disease forecasting system available in North Dakota. NDSU coordinates with North Dakota Agricultural Weather Network (NDAWN) sites across the state to make fungicide spray decisions.

 

The continued rain showers have resulted in long dew periods at many NDAWN sites, which are favorable for infection and disease development.    Disease models are confirming a risk of tan spot infection in many areas in the state.
The NDSU small-grain disease forecasting system also information for the risk of late season tan spot and other Leaf spot infections in the web: www.ag.ndsu.nodak.edu/cropdisease/
On appearance of tan spot, an early season fungicide application may be warranted for disease management. Quite a few fungicides from triazole and strobilurin groups are available for early season sprays to manage tan spot (refer to 2013 North Dakota Field Crop Fungicide Guide for the latest options). Generally for early season tan spot control, half the full label rates can be used. Sprays can also be tank mixed with early herbicide application, generally at the 4-5 leaf stage.  For more information about tan spot refer to NDSU Extension bulletin PP-1249