Knowledgebase
Sick apple tree #585979
Asked August 03, 2019, 11:32 AM EDT
Denver County Colorado
Expert Response
It is difficult to tell from the photos what disease or insect is attacking your tree. Coddling moth is a common disease in crabapple trees in this region.
CSU fact sheet:
https://extension.colostate.edu/topic-areas/yard-garden/backyard-orchard-apples-and-pears-2-800/
But other diseases including fungal diseases are also seen in the apple trees. A Neem oil with an appropriate insecticidal spray would potentially provide the best control of the disease or insect. Included with this answer is a fact sheet on history and controls for crabapple diseases and insects.
Suggest taking some of the diseased leaves and the white substance on the trunk to a local nursery for identification. There are at least two sites in the Denver area for diagnosing the exact attacking agent: Jefferson County Fairgrounds has a CSU site and 888 Iliff is the Denver CSU site.
Probably impossible but If the hive could be moved away from the crabapple tree, the potential for harming bees during spraying treatments could be reduced.