To spray today or not to spray today: that is but one of many questions. I won’t name the tank mix used, but see if you can relate to these considerations for weed control in my flax crop.
Crop staging is an issue for the broadleaf herbicide. The best crop tolerance is between two and four inches of height, but best control is when weeds are less than two inches in height or diameter. Since crop and weed growth are often variable, the best timing is a judgment call.
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To complicate the issue further, this particular broadleaf product on this particular crop (flax) shouldn’t be applied when the daytime high temperature exceeds 27 C two days before or after application. Otherwise, there’s increased risk of crop injury.
But the broadleaf herbicide is being mixed with a grassy weed killer and that product, according to the chemical rep, should only be applied when the overnight low temperature is 7 C or higher. Otherwise, wild oat control could be compromised.
This temperature advice isn’t on the product label or in the Crop Protection Guide, but the herbicide rep should know what he’s talking about. Good thing I ran into him.
So now there’s crop staging, weed staging, a maximum temperature and a minimum temperature. Oh, and if you read the product labels, reduced weed control and increased crop injury could result if there’s drought stress.
Let’s see. Virtually no rain in the past six weeks. Yup, that would probably qualify as drought stress, but the crop will be stressed a whole lot more if those weeds aren’t killed.
Ready to spray. It’s a few days since the last overnight frost. Expected high temperatures are just below 27 C. The flax is nearing the best stage for tolerance. Some is still a bit smaller than two inches, but everything is stunted in dry conditions.
The wild oats are running rampant in some parts of the field, stealing moisture that’s in critically short supply so there’s some urgency to get them stopped.
Better get up early to beat the wind. Whoops. The Crop Protection Guide says spraying during early morning may increase the risk of flax injury. Wonder what their definition of “early morning” is.
Got the mixing order figured out. Both products are emulsifiable concentrates, so it shouldn’t matter which one goes in the tank first, but the adjuvant has to go in the tank last.
The rep and the retailer both note there’s some antagonism between the two products so rather than 40 acres per jug of the wild oat killer, the rate should be increased to 30 acres per jug. Didn’t see that on the label or in the book.
The water volume recommended for the broadleaf product is 20 to 40 litres per acre. The wild oat chemical is a minimum of 40, so 40 it is.
I hope I haven’t sprayed too early. I hope the day doesn’t get too hot. Just after mid-morning, it’s too windy and I stop spraying. Clouds pass by and 10 raindrops fall. Don’t have to worry about rainfall reducing efficacy.
Resume spraying early evening. As I leave the field, I notice the first-sprayed flax is tilted over and not looking very happy. Hope it recovers.
Need to finish the flax and move on to other crops, other products with different restrictions and worries. I hope it rains or none of this will matter.
