Canola Watch quiz – Herbicide-resistant weeds Jay Whetter June 13, 2019 Leave a Comment 1. An 'Economics of Herbicide Resistance' factsheet at manageresistancenow.ca says that approximately what percentage of Canadian farmers are affected by herbicide-resistant weeds?20406080 2. Patches of herbicide-resistant weeds usually develop through a process of 'selection'. The website manageresistancenow.ca describes the development of herbicide resistance in four steps. Step 1: A very small number of weeds in the populations are naturally resistant to certain types of herbicides. Step 2: When the herbicide is used, it controls almost all the weeds in a population. Step 3: Survivors are resistant to the herbicide and lead to the next generation of resistant weeds. What does the website describe as Step 4?Applying herbicides with the same mode of action repeatedly enables the resistant population to multiply.Environmental conditions allow these resistant weeds to flourish.Harvest practices distribute these weed seeds all across the field.There is no step 4 if farmers use mowing or tillage to remove suspicious weeds. 3. Group 1 clethodim can be tank mixed with Group 10 glufosinate to enhance grassy weed control in Liberty Link canola, but what if the field has a lot of Group-1 resistant wild oats? Growers can improve glufosinate activity on grassy weeds by using the 10-gallon-per-acre water rate and _______________.Slowing down to reduce water pressureSpraying on a cloudy day to reduce evaporationSpraying on a warm, sunny dayUsing nozzles with a wide spray pattern 4. Important clues that a patch of weeds are herbicide resistant include:The patch has a distinct tear drop shape and has lots of weed species present.The patch contains weeds that are not on the label for the product applied.The patch is at the edge of the field where new weeds tend to enter.The patch has no clear shape and has only one weed type remaining while other weeds are dead. 5. If you suspect a patch of weeds is resistant, what can you do?Use a localized spray with a different product to get rid of it.Collect a few for analysis.Use mechanical means (tillage, mowing, rouging) to remove it before the weeds set seed.Adjust herbicide and cropping practices so that weeds can be sprayed with multiple modes of action that are effective on that patch and other at-risk weeds.All of the above Loading...
