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Growers make many decisions every year about what chemicals to use for pest prevention and/or control. These are very important and, often, expensive decisions to make. Unfortunately, sometimes we get less than desirable results from chemical applications.

Many factors influence the efficacy of chemicals. One simple factor we often overlook is coverage. We assume we are getting adequate coverage when we really are not. It is important for growers to pay close attention to their spray equipment. When spraying fungicides it is imperative to get thorough coverage.  Vegetables crops typically have dense foliage which can be difficult for spray droplets to penetrate. Most fungicides recommend using at least 20-30 gallons of water per acre on vegetable crops.  In order to achieve higher spray rates without run-off you must also adjust sprayer pressures accordingly. Increasing sprayer pressure will create finer droplets resulting in better coverage; however, smaller droplet sizes will increase the risk of off-target drift issues.  Therefore, growers need to pay close attention to environmental conditions when spraying.  It is also a good idea to add anti-drift aid products to your spray solutions.

There are many types of sprayers to choose from, I feel one of the best sprayers for vegetable production is an Air Blast Sprayer. Air blast sprayers use a large fan to create a powerful column of air that blows the spray solution onto the crop. Air blast sprayers come in many different configurations. In general, they typically put out a large volume of spray solution, and can easily handle rates of 50 + gallons of solution per acre.  The column of high velocity air produced by this type of sprayer not only creates very fine spray particles it also causes the spray to penetrate deep into the crop canopy, resulting in excellent spray coverage. 

Obviously not all growers have access to air blast equipment; however, I have seen many homemade sprayers that do an adequate job as well. By utilizing different types of sprayer tips and playing with spray pressures growers can increase the performance of their existing sprayers.  Just keep in mind that it is imperative to accurately calibrate your sprayer before applying any chemicals.

Regardless which type of sprayer is used growers must pay close attention to sprayer tip selection, pressure and calibration to ensure proper coverage. By eliminating just a few of these potential problems, growers can help ensure they will get the most out of their chemical applications.        


Neil Kelly

Regional Extension Agent 


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