..... one of the dissectum variants of
Acer palmatum (Japanese maple). It's not clear what damage or issue needs remediation, but high heat, too much sun, and too little water can cause appearance issues with foliage that includes necrotic leaf tips and margins or entire leaves or branches dying or being shed.
"Neem" covers a lot of territory. There are good products and snake oil that touts the product as containing neem oil even though the extraction (of the oil) process might well have destroyed the chemical nature of the active ingredient (azadirachtin) which provides the products insecticidal and anti-fungal properties.
As an insecticide, neem oils doesn't have much in the way of instant knockdown. Its effectiveness as an insecticide is as an anti-feedant (upsets digestion of the insects that feed on sap), an anti-feedant, an oviposition deterrent (anti-egg laying), a growth inhibitor, a mating disruptor, and a chemosterilizer. Azadirachtin, a tetranortriterpenoid compound, closely mimics the hormone ecdysone, which is necessary for reproduction in insects. When present, it takes the place of the real hormone and thus disrupts not only the feeding process, but the metamorphic transition as well, disrupting molting. It interferes with the formation of chitin (insect "skin") and stops pupation in larvae, thus short-circuiting the insect life cycle. It also inhibits flight ability, helping stop insect spread geographically.
The product with the most active ingredient is pure, cold-pressed neem oil, with no additives or vehicle (helps facilitate applications) added. If you decide to use it, ask how to use with the greatest efficacy. The product is highly reactive to alkaline hydrolysis, which means it should be used with water from a reverse osmosis filtration system, distilled water, or otherwise deionized water - air conditioner or dehumidifier condensate, rainwater or snow melt, e.g., and the water should be acidified with white vinegar or citric acid.
What benefit were/are you expecting from neem oil applications? It's also a so-so fungicide and like most fungicides it works best as a prophylactic as opposed to a remedial measure.
Al
