Leaf Curl

Question: I have a plum tree that I planted about 2 years ago and this year like last year the leaves are doing this Leaf Curl thing. The leaves coming out now are curling up. I am using Safer Brand insecitidal soap. Just did 2 sprays on the new leaves. this is the only tree I see this happening on.

responder: Best Regards,   Replied May 01, 2023, 7:30 PM EDT
response: Dear Reed,  Thank you for contacting Ask Extension about the curled leaves on your plum tree.  It is most likely that your tree has leaf curl plum aphids (Brachycaudus helichrysiI ). Insecticidal sprays are only effective if you are able to spray the insects directly, but leaf curl plum aphids protect themselves by hiding inside the curled leaves. Here is information about their life cycle: https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=46524#:~:text=Unlike%20leaf%20curl%20in%20peaches,leaves%2C%20causing%20them%20to%20curl.  It may be too late to actually control the aphids this year. They will move on in a few weeks. But, as indicated in the article, avoid over-fertilizing especially with nitrogen fertilizers that stimulate new foliage.   Early next spring, steps can be taken to control the pests. Before the leaves are large enough for the aphids to hide in, use a strong jet of water to knock the aphids off the leaves. Alternatively, you can spray the tree with horticultural oil just as the leaf buds are swelling.   I hope this information is helpful. Please write again if you have additional questions.

responder: The Question Asker Replied May 01, 2023, 10:09 PM EDT
response: Re: Leaf Curl (#0097756) Is there any particular Horticultural oil I should get? I am seeing that there are so many types of this oil, it's dizzying. Monterey seems to be out there a lot, but there seems to be different types. Dormant oil, all season oil etc. Thanks so much for all of your help. Its truly appreciated. Stay Well and Be Blessed.REED BUCKLEY<personal data hidden>Rndfakefoodplus.comOn Mon, May 1, 2023 at 4:30 PM Ask Extension <<personal data hidden>> wrote:

responder: Best Regards,   Replied May 02, 2023, 2:16 AM EDT
response: Dear Reed,  Horticultural oils that are applied for cool-season control of overwintering pests on trees and shrubs have historically been referred to as “dormant oils.” Those used during the growing season have been referred to as “summer oils.”  Many horticultural oils currently on the market can be used in any season so long as you follow the label directions. Be sure to read the label completely to use the product effectively without harm to bees, fish, waterways, etc.   Note that these oils work by suffocating the pest and must come in direct contact with the pest. It will not be effective once the aphids are hidden in their protective leaf curl. This is why I recommended applying horticultural oil when the leaf buds are swelling in early spring as the aphids are initially present.  As a matter of policy, Extension does not allow us to recommend brand-name products. However, product labels will give you the information you need. It should list the specific plant you are treating, the type of pest, and the season. Using this information, any reputable brand will do.  I hope this answers your question.