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The Global Invasive Species Team | |
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Global Invasive Species Team listserve digest #031 Tue, 18 May 1999 12:20:27 -0700 (PDT) --CONTENTS-- 1. Setting concentrations in backpack sprayers 2. Weed spraying conversions 3. Invasion-proof communities? --------------------------------------- 1. Setting concentrations in backpack sprayers From: Barry Rice (bamrice(at)ucdavis.edu) Chris Helzer wanted to know about how to convert herbicide application rates (usually expressed in quarts or pounds per acre) to dilution rates in backpack sprayers. There is a long and a short answer to this, depending upon the intended use. -Short Answer (for spot spraying) If the application rate calls for X lbs acid equivalent of herbicide per acre, just change that to a dilution rate of X percent. For example, if you want to apply 1.5 lb a.e. Roundup, dilute it to 1.5%. Spray the plant so it is wet, but not dripping. Thanks to Tom Lanini and Joe DiTomaso (both UC Davis) for these approximations. -Long Answer (for larger jobs and more area coverage) If you are using the backpack sprayer to cover a larger area (such as a dense monoculture infestation of grasses, iceplant, groundcover, etc.), you must calibrate your application rate carefully. This is how you do it. Step 1: Get your backpack sprayer ready just as you would for an herbicide application, but use water in your tank instead of herbicide. Carefully measure how much water you put in the tank (I will assume you use 1 gallons). Step 2: Use your rig to spray the ground until you run out of water (doing this on asphalt or concrete will help you see if you skip spots). Measure the area you covered: the area=length x width (for a rectangular area). It is crucial you do this calibration spray just like you would in the field, walking the same speed, spraying at the same height, keeping the pressure in the tank the same, etc. Step 3: Perform the following calculations The number of acres you sprayed is: (Area you sprayed in square feet)/43,560 = acres you sprayed The gallons/acre you sprayed is: 1 gallon/(acres you sprayed)=gallons/acre you sprayed If you used a volume of water other than 1 gallon, use it in the equation above. Step 4: Making your tank mix. To calculate your dilution rate, divide the desired herbicide application rate (e.g. oz per acre) by the spray rate (gallons per acre). For example, if you wanted to apply herbicide at 32 oz per acre, and you are spraying at 10 gallons fluid per acre, your tank mix should be: 32 oz/acre / 10 gallons/acre = 3.2 oz/gallon If you are using a 5 gallon tank, you can use 3.2 x 5 = 16 oz in your tank, diluted with water. Sorry for doing this in non-metric systems, but that's how it appears on most herbicide labels. --------------------------------------- 2. Weed spraying conversions From: Becky Waegell (bwaegell(at)cosumnes.org) Looking at my Roundup label I see that the general recomendation for perennial weed control is 1 qt per acre (broadcast) or 2% solution for backpack sprayers. 2% equates to 2 2/3 oz per gal. I however don't know if this conversion is something that can be applied across the board to all other herbicides. I would suggest that when in doubt on these things contact a Certified Pest Advisor (most ag chemical companies have them) and get them to provide an appropriate concentration for the herbicide you are using. --------------------------------------- 3. Invasion-proof communities? From: Barry Rice (bamrice(at)ucdavis.edu) An old notion regarding invasive species was that habitats with a large number of native species resist invasion by non-natives. It seems this may not be correct. New research indicates that any habitat with plenty of resources may be ripe for invasion. For a summary article on this research, turn your web browser to: http://www.usgs.gov/public/press/public_affairs/press_releases/pr820m.html |
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