Should you be using some of the modern reduced-AI copper fungicide products on YOUR treefruit crops in 2021?

Tucked away in Upstate New York with countless old farm homes that scatter the area, Wayne County is the 4th largest apple growing acreage in the US. Jeff consults for a vast majority of the growers in the area through his company called agr.assistance. On a weekly basis, he publishes an e-newsletter… here is a recent article he made regarding new copper fungicide products!

You’ve been hearing plenty the past few years about new and improved reduced-AI copper fungicide technologies- products like CS 2005. This newer copper formulation can both somewhat reduce the risk of fruit russetting and also lower the long-term elemental copper buildup in orchard soil environments. A potential win-win… So should you be using these reduced-AI copper fungicides on YOUR treefruit crops in 2021?

The QUICK answer is YES you should- at the very least in dormant sprays on your treefruit crops… * But a lb. of copper is a lb. of copper regardless of the formulation- right? – Apparently not quite and I’m not saying this because I’m a trained chemist- which clearly I am not. My opinion is based on both our trial results plus our first-hand commercial experiences with many of these new lower-AI copper fungicides over the past several growing seasons. They have performed quite well.

C’mon now- isn’t this just a way to sell me less actual copper for the same amount of money ? No doubt that’s one of the reasons that these reduced AI copper fungicide technologies were first developed. But they also address environmental concerns about heavy metal buildup in agricultural soils as well as looming concerns with excessive copper fungicide residues on harvested crops. * But seriously— how can applying LESS actual metallic copper fungicide possibly work as well? – It may seem like alchemy— but it’s actually nano-technology. All of these modern copper products consist of dramatically smaller particle sizes than older copper fungicide formulations- resulting in both improved fungicide coverage and potentially extended residual activity. * So what have WE actually seen out in real-world commercial orchards with these reduced AI new-and-improved copper chemistries?

CS 2005 (Magna-Bon II)- We’ve recommended plenty of CS 2005 in dormant sprays on apples over the past 10 seasons in western NY- with consistently excellent and cost-effective results as a key step in integrated fireblight control programs. (Dr. Kerik Cox Fire Blight Research Trial Results Here) And it has been very successfully used in Michigan as well. CS 2005 is a 100% water-soluble systemic copper sulfate pentahydrate formulation.

* So should you be using reduced-AI copper fungicides on YOUR treefruit crops? The FULL answer: • YES you should- at least in dormant sprays. You should be using them because they’re easier to apply, cost-effective and safer for the environment — plus they just plain work…

• However, I’d still proceed cautiously with potential bloom or post-bloom use of ANY copper fungicide products due to the risks of fruit russeting- especially on fresh market crops. I do believe that these new copper products are indeed somewhat “safer” to both plant foliage and to fruit than older higher-AI copper fungicides. And we have witnessed first-hand some surprisingly good apple fruit finish results where some of these new reduced AI copper products have been applied post-bloom. But we have also experienced some commercial apple fruit finish concerns where newer low-AI copper materials have been applied post-bloom. Always walk before you run…

Interested in having CS 2005 helping you in the orchard fight disease? Send us an email to for the closet distributor near you!

Jeff Alicandro of agr.assistance.

Crop Consultant in Wayne County, New York.