The organic tree specialist..i wonder now...was here to spray same mixture on my Leyland Cypress trees as a cure for Mites...I saw the product he used ..actually watched him mix it up in his truck...Against my wishes he sprayed the weeping cherry when he had finished the cypress treatment..The tree looked the best it had in 24 yeras its been there..so i said leave it alone...he said the spraying would be preventative...and did it anyway....within two days and now a week..and well over half the leaves have turned yellow and fallen off..Did he kill it?

I am assumng the products used are actually Impede and Neem oil :-)) And neither one should have much of a negative effect on a weeping cherry (although Lord knows they have enough other issues!!). Impede is just an insecticidal soap although at a somewhat higher concentration. And Neem oil is a go-to organic control for a variety of insect, fungal and mite issues.

Both of these are contact insecticides, so "preventative" is a bit wishful thinking. But even so, unlikely to do much harm I would guess that the timing of the spraying may be playing a role. A wide variety of plants can develop phytotoxic reactions to insecticidal soap (or other pesticides) if sprayed during sunny conditions. This can cause them to lose foliage or it to burn and dry. If provided with sufficient moisture, they will often releaf rather promptly, given reasonable weather conditions.

Thank you so much Gardengal48 for responding...You have the correct spelling on the products...sorry..i just spelled them as the tree guy pronounced them..figuring someone who knows about organic treatments...as you do...would understand...I am very upset with this problem.,,as this large beautiful tree is the focal point of the plantings around my pool...and I told him not to spray the tree, as it was fine...anyway..as per your post...will it releaf this year..Long Island NY...or next spring?...and can I now assume that the tree is not going to die from this...even with so few leaves?..And yes he sprayed it in sunny conditions...wish i had communicated with you before he did his work...ahhh depressing. Thank you very much again...look fwd to your post.