Lake Tahoe’s shrubs, willows a reminder of youth
A couple of years ago, I began noticing red growths on the manzanita leaves which appeared to be part of the leaf. I sent a picture of it to a friend who is also a genius when it comes to finding information and he discovered that it is a manzanita leaf gall aphid, Tamalia coweni.
Gall aphids are small, grayish or greenish insects that feed on plants, the process of which creates a gall.
A gall is an unusual growth of plant cells, occurring in late spring, when plant growth is most active. This active growth is stimulated by chemicals injected by the insect, along with its eggs. The chemicals stimulate the plant cells into a rapid and abnormal growth, forming a protective gall around the developing insect, which in turn, secretes more chemicals. In this way, the insect is protected from the elements and predators while it feeds and develops until fully mature.
The manzanita leaf gall will contain a tiny opening, which causes the gall to split open as it dries, allowing the mature insect to escape.
Gall-inducing insects are species-specific and there are many. I noticed the manzanita galls because they are bright red, easy to spot on the green leaves. These aphids are parasitic; however rarely do they do significant damage to the host plant.
And actually, the aphid galls are often invaded by another parasite, the Tamalia inquilina, an obligate parasite which cannot complete its lifecycle without a host.
Again, this parasite does not damage its host; rather they co-exist within the gall, initialized by the aphid. The two together are known as communal parasites, a form of mutual cooperation and passive tolerance.
When I first discovered these showy galls, I never would have imagined all the action taking place within.
Tiny wasps are perhaps the most common gall initiator, occurring mostly on oak trees and rose bushes. Rose galls form on the canes, a wild protrusion of hair-like growths. I haven’t seen one, but next time I find a thicket of rose bushes, I’ll examine it more closely to try to find one. The mature wasp emerges in the spring.
Dried and powdered, the rose wasp gall can be used to cure colic, as a diuretic, as a remedy against toothache and as an astringent.
Oak galls, when dried are called gall nuts, contain high levels of tannin which can be used in the tanning of leather; extracts are used in pharmaceuticals, as feed additives, dyes, inks and metallurgy — the science of studying the chemical and physical behavior of the elements.
While I was discovering manzanita galls, I saw the same phenomenon on the willow leaves. Willow is very susceptible to galls by many different kinds of insects. I believe the red galls in the photos to be made by the sawfly, a small fly with caterpillar-like larvae. It gets its common name from the saw-like appearance of its ovipositor, the organ used for depositing eggs. The female also uses this ovipositor for cutting into the leaf.
Willows are prone to midges and mites, as well as more than 100 species of aphids, with each type of insect creating a different type of gall.
Early last spring, I was walking in an area that is usually inaccessible in at that time of year, due to snow, mud or standing water, but because of the dry winter, I was walking there and found some long catkins, hanging from a willow that had yet to grow leaves.
The catkins emerge in very early spring and since willows tend to grow in wetter areas, I hadn’t seen them before. The catkin, which is actually a flower cluster, emerges before the leaves and this day they were abundant on the tree.
Willows are cross-fertile, making it possible to create hybrids in the wild, which may explain why they are difficult to identify. The willows I am seeing have different types of leaves, sometimes on the same branch. They also grow easily from cuttings. They spread widely and aggressively, seeking out water.
In ancient times, the leaves and bark of the willow tree were used as a remedy for aches and fevers. Native Americans relied on willow as a staple for their medical treatments.
I had a giant weeping willow, which is an ornamental hybrid, in my yard as a child so seeing the willows takes me back to the carefree days of barefoot childhood.
Toree Warfield is an avid nature lover, and writes this column to teach and stimulate interest in the marvels that surround us. See the new website: saveourplanetearth.com to read columns and to find links to bird song recordings, additional photos and other content.