Austrian Pine needle die back.

Asked October 12, 2017, 9:32 PM EDT

For two seasons in a row my Austrian Pines have exhibited needles dying starting from the trunk end of the branches in late summer. If I pull off the the brown needles my hand is covered with many tiny insects that are long and slim in length and appear to have wings. When smashed they leave an orange smear. The branches below have a black residue on the bark. I have sprayed Malathion and Bayer 3 in 1 Mite control but they are back in force in a week. I live in Castle Rock, CO and this same thing is occurring on Austrians on many of the trees on streets and in yards throughout the area. I wish that I could at least identify the insect and find a solution. So many Austrians are being defoliated, can you help?
Bob R

Douglas County Colorado trees and shrubs

2 Responses

I will have to see pictures of the trees to know if they have a problem. However, one of the most common questions people ask me is why their pine’s older, innermost needles are falling off at the end of the growing season. In nearly all cases it is the normal fall needle drop that happens every year at this time. The needles last 3-5 years and then die and fall off. Google “fall needle drop”and look at the pictures there and you will see lots of examples.

I was asked to chime in on this question. As Michael noted, fall needles browning in pines is normal, if browning needles are the oldest, innermost needles furthest back on twigs/branches. See Austrian pine photos attached.

As for black residue on bark, you are probably seeing it on topsides of branches mostly. It sounds like "black sooty mold", which grows on the honeydew (sugary waste product) secreted by aphids and other piercing/sucking insects. When aphids or related insects secrete honeydew, it drips down like sap onto the needles and tops of branches below (photo of aspen twig with black sooty mold).

So, my guess is that the needles drop is normal, not caused by the insects found in your Austrian pines. If this problem continues next year, bring in some of the insects for ID. The Extension office is on the Douglas County Fairgrounds in Castle Rock.