Once a month I have been following a tree, this year it is the turn of the Larch tree.
There are two Larches I am following one a Japanese Larch and the other a Common Larch.
You can see my monthly post here so far.
The cones have changed quite a bit over the past few month.
Now we are into May/June one of the biggest things to happen to this tree is it gets covered in
Woolly Larch Aphid
It is not on all the trees at the park, and I have not recorded many on the Japanese Larch. Some are covered more than others.
It's easy to spot...a bit like when you have left a white tissue in with your darks when washing, they come out covered in bits !!
The Strange Life of Adelgids: Adelgids have one of the most complicated life cycles you will find in the animal kingdom. All of the adelgid species have as their primary host one of the 35 or so species of spruce trees (genus Picea) and a secondary host that is another conifer, such as larch, hemlock, pine or fir. You’ll need a scorecard, but let me see if I can run through this quickly. It’s a cycle, so there’s no real beginning, but let’s start with the tiny winged adults that fly from the secondary host to the primary spruce tree host. Once they land on a spruce tree, the adelgids lay eggs and die, sheltering the eggs with their wings. The eggs hatch into males and females that lack wings, which go through four developmental “instars” before becoming adults that mate. The mated females lay a single large egg, which hatches into a wingless female. The female feeds and then induces the spruce tree to create a “gall,” which resembles a small cone. The gall is destined to become an adelgid nursery. In the spring, the female, after going through several instars, lays a clutch of eggs that hatch and move into and are enveloped by the growing gall. These larvae feed on the gall and go through several more instars. By mid-summer, the gall dries out and opens. The adelgids emerge and moult into winged adults, which migrate to the secondary host, a non-spruce conifer.
Got all that? Good. But stay tuned. There’s more.
Once the flying adelgids have settled on the secondary host, they lay eggs and die. The eggs hatch into females and grow, through several all female generations. It is these adelgids that feed with sometimes destructive result on larches and hemlocks. These are also the generations that lay eggs covered by waxy “wool.” Some of the eggs that hatch develop into the winged adults that fly back to the original spruce host to start the cycle all over again. Others develop into wingless females that stay on the secondary host (larch or hemlock). In the spring, these females grow and lay eggs and continue the generations on the secondary host. In this way, the infestation on the secondary host can grow and eventually kill the tree without ever needing the primary spruce host.
Phew! And we thought human life was complicated.