Gloomy Scale :(

[Dabbler]

I've been dealing with gloomy scale on this maple for a couple years now. While the tree doesn't stop growing like mad and doesn't seem to be affected it, it's really annoying to think I got all of them to see they it comes back in a few months Anyone have any advice as it has never gotten onto any of my other tree's.

 

[Wires_Guy_wires]

There are two types of bugs I use systemics for:
Scale aphids and wooly aphids.
Contact insecticides just don't work on them here, and I don't like spraying poison if it doesn't work.

Two consecutive treatments, 3 weeks apart, kills them all.

I'm combining lambda-cyhalothrin and acetamiprid in a single mixture and it works. Acetamiprid is being banned here though, so you might want to look at something else.

 

[Shibui]

Scale are hard to beat. You can kill the adults but eggs that hatch after treatment are free to recolonise.
Horticultural oils kill adult scale insects but does not affect eggs so if you use oils, retreat several times a few weeks apart.
Systemic insecticides circulate through the entire tree so anything that bites or sucks on the tree after treatment will die. many systemics are also active for a few weeks after treatment so will kill adults feeding as well as new hatchings for about a month. Note that systemics are not discriminatory and will be in every part of the plant including flowers. Systemics have been implicated in beehive deaths so please don't use these within a month of flowering.
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