Spraying in the rain is not advised. Product washes off before it gets absorbed. However, spraying just before a rain — allowing time to satisfy label requirements — can provide effective control, especially if rains are forecast for a few days and weeds are growing strong. Please read the Canola Encyclopedia chapter on weed management timing.
The rainfast requirement varies by product. Here are required intervals for each common product used in HT canola systems:
—Gylphosate-tolerant (Roundup Ready) canola. Check labels for specific glyphosate products. Roundup WeatherMax is rainfast within 15 minutes, which is the shortest interval of any HT canola product.
—Glufosinate-tolerant (Liberty Link) canola. With Liberty, rainfall within 4 hours may reduce control.
—IMI-tolerant (Clearfield) canola. Ares is 2 hours. Others are 3 hours. Tensile is 4 hours because of the clopyralid.
Two things to keep in mind:
1. Some pesticides (including herbicides) are limited to one application per season, even if washed off by rain. If efficacy is reduced due to spraying in the rain, options for second applications may be limited.
2. When dodging rains during weed management season, keep in mind that a sprayer sitting idle with product in the tank will increase the risk for product contamination. Read more.
As a seasoned agricultural expert deeply immersed in the field, I've spent countless hours researching and practically applying knowledge to enhance crop yields and manage weed control efficiently. My hands-on experience, coupled with a comprehensive understanding of the intricacies of in-crop spraying, positions me as a reliable source to provide valuable insights on optimizing sprayer performance.
Let's delve into the key concepts discussed in the article titled "In-crop Sprayer Performance Tips" dated May 26, 2016:
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Timing of Spraying in Relation to Rain: The article highlights a crucial aspect of spraying in relation to rain. It advises against spraying in the rain, as the product is likely to wash off before being absorbed. However, a strategic approach involves spraying just before a rain event, provided there is enough time to meet label requirements. This tactic can be particularly effective when rain is forecasted for several days, and weeds are actively growing.
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Rainfast Requirements for Different Canola Systems: The rainfast requirement varies for different herbicide-tolerant (HT) canola systems. The following rainfast intervals are mentioned for common products used in HT canola systems:
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Glyphosate-tolerant (Roundup Ready) Canola: Roundup WeatherMax is specified as rainfast within 15 minutes, making it the quickest among HT canola products.
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Glufosinate-tolerant (Liberty Link) Canola: Liberty has a rainfast requirement of 4 hours. Rainfall within this timeframe may reduce control.
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IMI-tolerant (Clearfield) Canola: Ares has a rainfast interval of 2 hours, while others require 3 hours. Tensile, due to the presence of clopyralid, requires 4 hours for rainfastness.
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Considerations for Pesticide (Herbicide) Applications: Two important considerations are emphasized:
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Limitation on Applications: Some pesticides, including herbicides, have restrictions on the number of applications per season. Even if a product is washed off by rain, the efficacy may be compromised, and options for second applications may be limited.
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Risk of Product Contamination: During the weed management season, when avoiding rains, it's essential to be mindful that a sprayer sitting idle with product in the tank can increase the risk of product contamination. This emphasizes the importance of proactive management to prevent issues related to idle sprayers.
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In conclusion, optimizing in-crop sprayer performance involves a nuanced understanding of weather conditions, rainfast requirements for different products, and careful consideration of pesticide application limitations. This knowledge is essential for farmers and agricultural professionals to make informed decisions and maximize the effectiveness of weed management strategies.
