Large mature azalea problems

Asked April 27, 2016, 12:40 PM EDT

I have a very old 5-6 foot azalea. Has two 5" caliper stalks at base, with additional smaller -- healthy looking. It is in a bed of similar large, old azaleas which seem fine. Unlike others, the affected azalea normally has larger, more fragile blossoms and slightly furry leaves. This azalea faces east and its east side is open to air and light; the other azaleas are adjacent on its west and north sides. Bed is at SE corner of our front porch (which faces south). In the last 4 years, we lost a nearby 200 year old oak, so azaleas have gotten more sun in recent years. Last fall, we noticed some dead branches on this one. Bark looked sooty; spots on leaves on both sides; no shininess. We took a cutting to Behnke's who identified the soot as insect poop and recommended Bonide All Seasons Horticultural & Dormant Spray Oil (active ingred 98% mineral oil). We sprayed once in the fall. Azalea looks the same this year and we THINK we saw tiny tiny white flying insects last week. It is drizzly this morning, and we see none. I have taken pictures from street (east facing west), closeup with hand, and from front porch - facing south (with rail - see dead branch emerging from center). Base branches look good and green; top has dead wood. What is the problem? Should I remove the dead branches? What else should I do? Thank you. PS forgot to mention. We sprayed Hort oil again about 2 weeks ago.

Montgomery County Maryland azaleas shrubs lichens dead branches

3 Responses

Based on your photos we cannot make an accurate diagnosis. We notice some lichen on the branches in the middle photo. Lichen can be common on mature shrubs but are not the reason for any decline. See more

Overall, the shrubs look pretty good. We do not see signs of insects or damage. Do not spray unless the pest has been identified and you know what you are spraying for. At this point, prune all dead wood. Scratch the branches with your fingernail and look for green tissue. If you see it, the branch is viable. If brown, prune back to healthy tissue. Azalea bark scale can cause sooty mold on bark, yellow leaves and twig dieback but we do not see it. It would be helpful to look at the attached publication for more information
Monitor the shrub throughout the growing season and when you notice
symptoms, send us photos so we can see what you are dealing with.

I have taken additional pictures to show insects. When we moved branches, there is a flutter of tiny flying white insects (see pictures). The damaged/dead branches are blackened (see pictures from first email) with some white spots. There are ants crawling on branches. Any additional thoughts? Thank you!

Thanks for the additional photos. The insects depicted in those photos are white flies. These are sucking insects that feed on the xylem of the plant, and like aphids and other sucking insects, they produce a waste product known as honeydew. As the name implies, the substance is sweet and sticky. It attracts ants and will usually promote the formation of a mold known as 'sooty mold'. Your description seems to corroborate this diagnosis.
Azaleas are also susceptible to lace bug damage. So, be sure to review the publication suggested in our earlier response.