Yes, it will harm it. Your tree isn't going to enter protective dormancy during a period of increasing day length, so it needs to be protected from frost and rapid temperature drops. Plants can suffer severe injury from cold, even if they don't freeze. An example might be moving a tree from a 70* house to a front porch when it's 35* - not enough to freeze the plant, but more than enough to cause chill injury.

My guess is that you weren't using cold-pressed neem oil and the damage wasn't from the neem itself, but from the vehicle or other additives in the concoction.

Why do you have it indoors in the first place?

Al

I have kept them inside this year becuase they were simply looking to beautiful to put into dormancy. Since they are Chinese elms they can skip a dormancy period every now and then. I have only placed them from indoor to out when the overnight low wont drop under 40.

FWIW - your trees will wake up with a LOT more energy in the spring and put on a LOT more growth in the next growth cycle if you give them a long, cold winter's rest. That's not to chastise you, it's simply informational.

You didn't mention what neem product you used - something other than cold-pressed oil?

Al

I wasn't taking anything you said hurtful. Sorry if i came off that way. The neem oil i have been using is "Neem 2" The maker is Green Light. I have tried a few otc brands and am having the same problem with most of them. I'm thinking of just buying a concentrait next time. Any suggestions?

Yes - The pure, cold-pressed neem oil that Dyna-Gro packages is a great product for use on insects with sucking/rasping mouthparts.

Al

Great. Just placed my order. what ratio would you mix it at? And also thanks for the advice