Dear Master Gardener,
Over time, wood-colored protrusions have developed at the base of each branch (please see picture), and I am wondering if they are a sign of disease? Please help me identify the issue. I don’t detect any scale, or aphid infection. The indoor plant is several years old. I am aware that it may need more light. The soil is kept relatively dry, though the humidity in the room remains about 60%. Thank you for your time – I really appreciate it.
Norfolk Island Pines (Araucaria heterophylla) prefer a moderately heated room, sun during the winter but some shade during the summer and do not like to be touched as their needles are delicate. Although these plants can be fussy about their environment, they are relatively free of diseases and pests. As you have mentioned the most common ones, scale and aphids, don’t appear to be the problem. There is a scale called an armoured scale that is known to be a pest of Norfolk Island Pine trees. Take a look at the photos in the following link to see if they match what is on your plant. If so, they include a description of how to deal with them. In your case, since it is on a single plant, removing them mechanically should suffice.
https://hortnews.extension.iastate.edu/scale-insects
I have not been able to find any other diseases that fit what is on the base of the branches. I have, however, seen some photos that show a similar formation and conclude that if it isn’t an armoured scale, it may just be a natural growth. If your plant continues to look healthy otherwise, I would not worry about it.
http://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?taxonid=276626