In her weekly newsletter, Growing Wonder with Felicia Alvarez: Simple Tips for Thriving Roses, Gardens & Homes, Felicia offers expert advice to help you cultivate stunning roses, vibrant gardens, and welcoming homes. Each edition features a subscriber-submitted question, where Felicia provides thoughtful answers to your rose, garden, and home-related queries. This Q&A was originally featured as a highlighted question from one of our subscribers, published in the newsletter.
Q: "Is it safe and possible to mix dormant spray (copper liquid) and insect and bug treatment (horticultural oil) in a sprayer and treat both at the same time?"
Submitted by: Lucie from New Fairfield, Connecticut - Zone 6A
- Liquid copper (copper fungicide) and horticultural oil can sometimes be mixed for dormant sprays, but ONLY if the product labels explicitly state they are compatible.
- Some copper formulations can react with oil, potentially causing phytotoxicity (leaf burn or bud damage).
- To minimize the risk if you aren't sure if more than one product can be tank mixed together, many growers apply copper first, allow it to dry and then follow up with horticultural oil a few days later.
- Always read and follow the product labels for mixing guidelines.
- If the labels indicate compatibility you can perform a jar test (mix a small amount in a jar to check for any reactions).
- When in doubt, apply the products separately—copper first, oil a few days later.
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