With some pests, no matter how closely one looks at the foliage, no signs of active infestation come to light. Slide the same tree out of its pot and it’s another story.
Root adelgid on young black pine roots
Root aphids and adelgids are insects that feed primarily on their hosts’ roots. There exist numerous species that feed solely on the roots of conifers. Deciduous varieties too succumb to their own root adelgid and aphid species.
Treatment isn’t exactly like it is for their above-ground counterparts as you can’t always remove the trees from their pots. And because roots are sensitive, it’s important to consider the phytotoxicity of any pesticides.
As with other infestations, keeping trees healthy is the best preventative. I often find infestations in overgrown specimens that dry out quickly, but root-feeding insects can show up anywhere.
Systemic pesticides can work well when necessary, though I usually scrape away what I can during repotting and watch the watering carefully through winter. If the tree is healthy, that will often do the trick. Additional stress caused by radical root work or severe cutback and bending can slow a tree’s recovery from infestation, so I’m likely to take a light approach when I see lots of the critters and postpone more stressful work for when the tree is healthy.
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will you please post a picture of affected foliage? thanks jonas!
zack Clayton says
I think what is concerning here is that looking at the picture most people I know would say, “Oh, it has nice microrhyza.” For those people how would you differentiate fungus from adelgids?
Jonas Dupuich says
Good point Zack – I’m looking to write about the difference between micorrhizae and the root pests, as well as non-beneficial root fungus before too long. All are similar with subtle differences between them. The very brief version is that micorrhizae I’m used to seeing on my pines looks white and “web-like” whereas the adelgid infestation looks more like clusters of small white puffs.
@mybabyciv – there’s no sign of infestation in the foliage when the bugs are below the surface. In bad cases, the foliage would turn weak or yellow, however these are symptoms of a number of maladies.