Tiny white flying insects
My outdoor plants are infested with tiny, white flying insects that primarily live on the underside of leaves. They also collect in the soil. I have been spraying with a water and Neem oil insecticide but it doesn't seem to keep them away for very long. What are these insects? Should I up the concentration of the spray?
The tiny white insect you describe is most likely greenhouse whitefly and can be transported from the greenhouse to the garden via transplanted plants in the spring and will not survive outdoors in Colorado during the winter. There are several different species but all can be treated in a similar manner. This fact sheet from Colorado State University will give you helpful information on the identification and control of whitefly. http://extension.colostate.edu/topic-areas/insects/greenhouse-whitefly-5-587/