Is it ok to spray my garden with Neem oil or insecticidal soap early in the morning or will it burn the plants as the sun gets more intense as the day progresses?
If there is a need to spray early morning is a good time to do that so the sun light will not adversly react with your spray and the insects are still too sluggish to move around to avoid the spray. 6 or 7 am should be early enough so the spray would dry before the suns intensity could cause harm.
Don't forget, kimmsr...Neem doesn't act as a contact killer. It needs to be ingested by the pest insect in order to be effective. As a matter of fact, if you spray over the top of the pests, you'll be disappointed in that they don't fall over and die right away.
The best time to apply Neem is probably in the evening. However, if you aren't having severely hot summer temperatures, the early morning would be fine. Make sure that the plants are well hydrated, as you would with any product.
If Neem Oil coats an insect and prevents it from breathing it is a contact poison. That is what is described by this article from the people at UCONN.
Here is a link that might be useful: How Neem Oil Works