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To spray or not to spray?

Keep these considerations in mind to avoid making unnecessary pesticide applications.

June 12, 2024

2 Min Read
A sprayer applying pesticides to a field
IS IT NECESSARY? Before you decide to spray herbicide, fungicide or insecticide, consider if the economic threshold for that pest is met. Tom J. Bechman

by Tony Bailey

Scouting early and often is key to any disease or Integrated Pest Management program. For a plant disease to occur, three elements must exist simultaneously: a susceptible host, a disease-causing pathogen and an environment suitable for disease development. It’s important to properly identify all diseases and pest species. 

Application considerations

If economic treatment thresholds have been met and foliar fungicide applications are planned, be sure to follow these recommendations, as applicable: 

  • Determine if spray tank water quality — hardness and pH — is an issue and address it.

  • Pay attention to different product formulations.

  • Determine the application rate and correctly measure the amount of product needed.

  • Calibrate the sprayer.

  • Determine the proper coverage, spray solution volume and pressure.

  • Select the proper nozzle.

  • If applicable, select the proper spray additives, like AMS or surfactants.

  • Identify and follow the proper mixing order of products to be used.

  • Beware of potential antagonism between pesticide products and additives. 

To reduce the potential of pests developing resistance, it is important not to use the same class of fungicides repeatedly. Plus, the fungicides need to be available if an outbreak occurs. Are applications being made for cosmetics or need? Be sure to leave test strips to confirm if applications paid for themselves and were warranted. 

If scouting determines that a foliar fungicide application is justified to treat a crop disease, do not add insecticides to this treatment unless economic thresholds also have been met for an insect or other pest. Even if your neighbor down the road has an issue, it doesn’t mean you do. Different management systems and field conditions will affect the likelihood of a pest being present in your field and at what level it will impact you. 

Natural defenders

Properly identify and consider all beneficial organisms while you are scouting for pests. This will give you the status and potential of your natural defenses against insect pest outbreaks. These beneficial species will be impacted by an insecticide treatment, and you may end up removing your natural crop defense system while trying to treat another issue.

If the targeted pest has not reached the economic threshold level, you may do more harm than good with an insecticide treatment. Encourage beneficial species with a soil health management system, including conservation practices such as no-till and strip till, cover crops, and buffers. Buffers provide habitat and a food source promoting beneficial organisms and pollinators. 

Proper identification and treatment of problematic disease and pests along with IPM strategies can help to reduce damage from making unnecessary pesticide applications. IPM is important to maintain the gains that have been made in conservation agriculture and to improve all conservation cropping systems. 

Bailey is state conservation agronomist with the Natural Resources Conservation Service in Indiana. He writes on behalf of the Indiana Conservation Partnership.

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