Residual Herbicides in Sprayers Can Cause Serious Crop Damage
Penn State Extension is highlighting the importance of thoroughly cleaning spray equipment throughout the growing season to reduce the risk of pesticide contamination and protect crop health. As weather conditions continue to vary across, growers are moving into a busy period of herbicide, fungicide, and insecticide applications.
This season has brought a mix of excessive rainfall and flooding in the midwest, while some areas have experienced excess heat and dry weather. With narrow opportunities for field applications, producers often need to complete treatments quickly, making proper sprayer maintenance even more important.
Residual herbicides left inside tanks, hoses, booms, filters, screens, and nozzles can damage sensitive crops during later applications. Because many modern herbicides are effective at very low use rates, even tiny amounts remaining in spray equipment may cause symptoms such as leaf cupping, twisting, and plant deformities. A quick rinse after spraying is generally not enough to eliminate these residues.
Sprayer cleanout also plays an important role before fungicide applications. Fungicides are commonly mixed with insecticides, foliar nutrients, biological products, and adjuvants. These combinations may loosen herbicide residues that remain inside the sprayer, increasing the chance of unintended crop injury.
Penn State Extension educators Tosh Rung Mazzone and Stephen Campbell recommend carefully following the cleaning instructions listed on each pesticide label, as requirements differ among products.
Effective cleanout includes draining the sprayer completely, flushing the system with clean water, circulating an approved cleaning solution through the equipment, cleaning filters, strainers, nozzles, and screens separately, and performing a final rinse before the next application.
Maintaining detailed equipment cleaning records, wearing the required personal protective equipment, and properly disposing of rinse water according to regulations are additional practices that help support safe pesticide applications, protect crop performance, and reduce environmental risks.
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