Want to protect several cornus floridas from dogwood borers in zone 5/6 northwest NJ. Arborists explained that our favorite 15 foot Cornus florida native just died from borers. It was a native that was probably damaged by construction 20 years ago and died a long slow death. Was hoping for a clean simple solution avoiding nasty spraying. But my on-line research seems to indicate that Bayer Advanced Tree & Shrub does not work for clear winged dogwood borers. It does appear to work great for Pieris japonica lacebugs though. What is the best way to protect the Cornus floridas? Also have some kousas. Do these need to be protected from the borers if they are otherwise very healthy?
The arborist was kind enough to mention that there was a systemic that I could apply myself to save money while we focused my remaining budget on things his people could do better than me. When I went to Lowes, a pretty knowledgeable fellow (but not an expert) said he thought that the Bayer Advanced Tree & Shrub systemic would do the job. I sent an email to the arborist requesting which systemic to buy but he hasn't responded.
I forgot to mention that the arborist did mention that the best thing I could do for the general health of the Cornus florida was to each year add shredded leaves to the area within the drip line or so and then put the mulch back on that.
for borers I believe the latest chemical products would contain Lindane or Endosulfan. at least up here those were the last ones I saw labelled for borers. You could consider Dimethoate but I dont think it did much vs borers. mulching may keep the tree a bit happier but certainly wont eradicate a borer infestation. There may be injectable products that would help, check the Mauger website for potential products then find a reputable company to apply them for you if that seems your best recourse.
