Hello,

Thank you for reaching out to MSU’s Ask Extension. According to the National Pesticide Information Center through Oregon State University, neem oil is practically non-toxic to plants, birds, mammals, and bees. However, Azadirachtin, a component of neem oil, is moderately toxic to fish and other aquatic animals. It is important to remember that insects must eat the treated plant to be killed. Therefore, bees and other pollinators are not likely to be harmed. Bees are most active during the day, so it is best to spray neem oil late in the evening or in the early morning when pollinators are not present to minimize contact. Another approach to combating aphids is to start checking your roses now as new growth is emerging to see if aphids are starting to show up. If you do see them, spraying with a strong stream of water early in the morning can kill them or at least dislodge them effectively reducing their population. A strong blast of water can also damage their bodies while knocking them off the rose and they will not be able to return. I’ve included a few links below with additional information.

https://www.canr.msu.edu/news/how-to-control-invasive-pests-while-protecting-pollinators-and-other-beneficial-insects

https://ipm.ucanr.edu/PMG/PESTNOTES/pn7404.html

https://solvepestproblems.oregonstate.edu/plant-problems/rose/aphid

https://npic.orst.edu/factsheets/neemgen.html

Thank you for your question!

Linda P, MSU Extension Master Gardener Volunteer

You may also contact the toll free MSU Extension lawn and garden hotline at <personal data hidden> with your gardening questions or visit www.migarden.msu.edu for Smart Gardening resources.