Calibration
Calibrating
Calibration of equipment used to distribute poison bait is important for effective pest control and protection of the environment and human health. Calibration also helps to assure that you are not wasting resources by distributing too much bait.
You can use a variety of rotary spreaders available at your local hardware or farm supply store.
In the event that the operator chooses to forgo the most precise method, follow the calibration directions below to determine a quick and relatively accurate application rate.
Calibrating bait spread.
Calibration directions:
Before you begin, you must calculate how many kernels per sqaure foot you need for the desired application rate.
application rate (lbs./acre) x # of kernels per lb. of grain = ___kenels/ sq. foot
43,560 (sq. feet in an acre)
If your application rate is 10 lbs./acre, and the # of kenels per lb. of grain is 18,000, your desired #of kenels/ sq. foot is:
(10 x 18,000)/43,560 = 4.13 kernels per sq. foot. (goal)
4.13 kernels per square foot is your goal to achieve the desired application rate.
Note: The number of bait kernels or pieces will vary according to the bait type and, with natural grain baits, the inherant variablility in grain lots. Often the number of kernels/lb is not easily available. However, we feel an average for oats of 18,000 kernels/lb is adequate for most situations.
Now, on to the actual calibration:
1. Find a clean, flat area or lay out a tarp that is at least 25 feet long and about 4 ft. wide. This will be your test area.
2. Fill the hopper of your spreader with clean oats (like the bait material) and walk over the middle of the test area (the short way) while turning the crank at a set rate per step. (Be sure to start turning the crank before you reach the test area and continue until you have cleared the test area.)
Calibration square.
3. Count the number of oats in 1 square foot sections the entire length that the oats are distributed in the test area or on the tarp. Document these numbers found. If the oats span 20 feet long, you should have counted between 10 and 20 random squares from end to end. (It is important that you count random squares and not just the areas where the most kernels lie.)
4. Repeat #2-3 at least 4 more times.
5. Now find the average number of oats per square foot for each trial run. Average all five trials. Compare this average # oats/ sq. foot to your goal # of oats/sq. foot calculated above. Adjust the spreader accordingly until your average and your goal are close.
Note:
- In trials conducted at U.C. Davis using this method for clean, rolled oats, it was found that with any given spreader, there may be anywhere from 0 to 15 kernels in the random squares that were counted. However, if the proper application rate of 10 lbs. per acre is reached, then the average of the random squares was always within 4-6 kernels per square foot.
Broadcast baiting by hand. - The current label for broadcasting chlorophacinone 0.01% and diphacinone 0.01% recommends that the bait be applied at a rate of 10 pounds per acre; this works out to just over 4 kernels of grain per square foot. However, due to the tendency of the rotary spreaders to distribute the bait unevenly, it is unlikely that you will get exactly that rate in each square foot. Multiple trials are recommended to ensure an average of approximately 4-5 kernels per square foot.
- The curent recommendation for zinc phosphide is that it be distributed at a rate 5-10 pounds per acre. Then the average number of kernels per square foot should be 2-5 kernels.
Frequently Asked Questions
- What if I can't reach an average of 4 kernels per square foot?
Open the spreader to a wider setting.
- I still can't get 4 kernels per foot. Now what do I do?
You may have to overlap your passes with the spreader, or walk at a slightly slower pace.
- What do I do if I get over 6 kernels per square foot at the lowest setting?
Walk at a slightly faster pace and widen your passes.
*With the small hand held spreaders purchased at a local hardware store, the desired output was reached when the spreaders were on the highest setting and the operator was walking at a speed of 2.5 mph, turning the crank at about one rotation per second.