Steven,

Thanks for contacting us about your crabapple tree. The white spots appear to be woolly apple aphids. The white fuzz is actually waxy threads the insect produces to protect itself from other insects, birds, etc. Aphids are sucking insects that eat the sap within the tree – very often found at twig/branch junctures like your pictures indicate. All of the sticky stuff you are seeing is honeydew – aphid poop – that they secrete (the tree is not oozing – the aphids are!). Because what they eat (sap) is high in sugar, so is the honeydew (thus the name). The honeydew often attracts wasps, ants and other wildlife that lap up the sweet treat. Fascinating, really. Nothing going to waste…Those insects will not harm the tree, but the aphids can when there are high enough populations of them. These aphids overwinter on elm trees, and move to apple, crabapple, and mountain ash for the summer to feed and reproduce. You may start seeing other life stages. Lots more details in the second fact sheet below.

An effective way of controlling them is to use horticultural oil, which smothers the insects and interrupts the feeding (which can introduce viruses into the tree). See https://extension.colostate.edu/topic-areas/insects/insect-control-horticultural-oils-5-569/

Another fact sheet on aphids has multiple options for controlling aphids (see the bottom area on management). https://extension.colostate.edu/topic-areas/insects/aphids-on-shade-trees-and-ornamentals-5-511/

Karin