is insecticidal safe for Chinese Elms ?

Hello All,

I have a Chinese Elm tree that was infested with scale (or possibly aphids) mid summer of last year. Because of the infestation I had a bad case of Sooty Mold that grew on what I assume was the Honey Dew secretions from the insects. I sprayed the tree with "Rotenone Pyrethrins" once a week for a three weeks. This seemed to clear up the bug problem because as I watered the sooty mold began to disappear, mainly on the lower portion of the tree.

It is now spring here in New York State. The buds on this Chinese Elm are just beginning to appear. I would like to do something to kill any larva that may have overwintered. Assuming some of the scale larva survived it safe and effective to use Insecticidal soap in the hope of suffocating the scale ? I am also considering using a soft bristle tooth brush with the insecticidal soap to scrub off a lot of the remaining sooty mold. Is this a good idea ?

Many thanks,
Gregg

Since we have no idea where you live, there's no way to know whether anything could have overwintered. But you likely had aphids. Scale isn't often the source of sooty mold. And if you had aphids, there was nothing to overwinter.

There's no point in spraying anything when there are no insects present. Modern insecticides do not have enough residual action to make preventative spraying useful -- much as people would like to think it does do something.

If you see aphids again -- and they're most likely to appear while all the leaves are young -- your Pyrethrin-Rotenone spray is ideal for the job. But please spray in the evening; your tree won't care and daytime spraying with that stuff also kills a lot of good bugs -- pollinators, etc.

Thank you for your response to my question regarding the use of insecticidal soap.

In the body of my message I did say that " it is Spring here in New York State.

thanks again
Gregg

New York State ranges from Zone 3 to 7.
Iris