Dark Foliage Like Oil On Conifers

Question

Hi we have 4 of these trees about 1m to 2 m apart. They are dark on the bottoms like an oily residue. What cam it be? Can we save them

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Answer 1

It could be sooty mold, a result of an insect infestation such as aphids or scale. The insects leave a honeydew film that can develop sooty mold. It also could be a type of blight or canker. Blight can produce grayish leaves. These articles should help:

https://extension.colostate.edu/topic-areas/insects/scale-insects-affecting-conifers-5-514/

https://ipm.ucanr.edu/PMG/PESTNOTES/pn7408.html

https://www.gardeningknowhow.com/ornamental/shrubs/juniper/juniper-twig-blight-disease.htm

https://www.gardeningknowhow.com/ornamental/trees/tgen/brown-conifer-needles.htm

https://www.gardeningknowhow.com/plant-problems/disease/cytospora-canker-disease.htm

https://hgic.clemson.edu/factsheet/leyland-cypress-diseases-insects-related-pests/

https://www.gardeningknowhow.com/ornamental/trees/arborvitae/arborvitae-plant-varieties.htm

https://www.gardeningknowhow.com/ornamental/trees/tgen/scale-leaf-evergreen-varieties.htm