The gall of it all
If plants were to get busted, they'd all have GUI's.
Every plant can be charged with growing under the influence of bugs, mites, fungus, nematodes, and a host of other creatures. The irrefutable evidence of GUI is the presence of galls.
What's a gall? You've probably seen a gall or two - those bizarre bumpy things on oak twigs, the swellings on goldenrod stems, blisters on hackberry leaves, and spiky projections on cherry leaves. A gall can be caused by any number of insects, an assortment of arachnids, and myriad microorganisms who enter or injure the plant, thereby triggering an orgy of plant cell reproduction.
From the invader's perspective, galls are a way of making a nursery for its young. From the plant's perspective, a gall is a response to an irritation.
Take the goldenrod gall fly, for example. Very cool little insect. Eurosta solidaginis, as it is known in some circles, is a small fruit fly - about 7 to 9 mm long - and a weak flier who would rather crawl than take wing. After mating in early summer, the female looks for a goldenrod plant. She searches visually but then tastes to be sure she has an appropriate goldenrod.
"The female fly walks over the bud 'tasting' it with chemical sensors on her feet and antennae," explains Dr. Warren Abrahamson and Paul Heinrich of Bucknell University. "If the plant is acceptable, she will then attempt to (puncture) the bud."
She does this with a structure called an ovipositor - the female's tool for laying eggs. Once her eggs are successfully deposited in the goldenrod, off she goes, leaving her future young to their own devices.
The goldenrod gall fly egg, safely ensconced in the goldenrod plant, develops into a larva. The larva secretes a chemical that induces plant cell reproduction. A riot of growth ensues. The resulting gall is a complex structure with a hard, corky outside and an interior of soft, nutritious plant food.
The goldenrod gall is a perfect fortress - and pantry - for the developing fly. Slowly munching away on the food inside the gall, the larva grows and grows. By fall, it excavates an exit tunnel but it's not yet ready to leave home. A thin layer of plant tissue remains at the end of the tunnel to protect the still-developing larva from the cold, cruel world outside the gall. The larva retreats back into the center of the gall to spend the winter in diapause, a form of dormancy.
Life gets a little dicey at this point for the goldenrod gall fly larva. Woodpeckers and chickadees seize the opportunity for a cold-weather snack and peck away at the hardened galls, often scoring a larva snack. Larvae that avoid this fate hang out inside the gall till the first hint of spring.
At this point, the larva enters its pupal stage. After two to three weeks, the pupae emerge as adult flies, and the goldenrod gall fly cycle begins again.
Another cool gall maker on goldenrod plants is the goldenrod gall midge, or Rhopalomyia solidaginis. This little insect lays eggs in leaf buds, inhibiting upward growth yet stimulating leaf production. The result is a dense spiral cluster of leaves, often referred to as a "rosette gall."
It's hard to find the critter in the mass of leaves, but if you work at it, you can part the leaves and feel the hardened center. Open it up with a pocket knife and take a look. Therein hides the gall midge larvae.
Other plants are hosts to a motley assortment of crazy looking galls. Hackberry trees are "galled" by psyllids, small insects that look like miniature cicadas. These little guys induce the hackberry to produce "nipple galls" which are common in summer and into the fall. Oaks are sought by many gall wasps, resulting in Gouty Oak Gall, Wooly Oak Gall, and Spotted Oak Apple Gall, to name a few.
Although unsightly, most galls do not injure the plant in the long run. There's no need to eradicate them for aesthetic or health reasons. An exception to this rule, however, is the fungus Gymnosporangium juniperi-virginianae. This gall-inducing fungus is a serious problem for apple growers.
In winter and spring, Gymnosporangium induces the juniper (also known as eastern red-cedar) to produce a pair of brown, kidney shaped galls on the branches. When spring rains comes, these galls transform into "gaudy bright orange masses of gelatinous spores (which) swell to several times their original size," as described by Jim Chatfield, Stephen Nameth, and C. Wayne Ellett in a paper published by The Ohio State University Extension Service.
"Spore masses are several inches in diameter, with a central core and radiating hornlike tendrils," they wrote.
These hideous-looking galls do not damage the juniper, but the juniper is only half the story. Those orange gall's spiny projections produce a prodigious quantity of airborne spores which then infect every apple tree within a two-mile radius. Once on apple trees, the fungus leads to leaf drop and fruit infection, thereby ruining the apple crop.
If most galls are harmless and some are destructive, are any useful? You bet! Galls are high in tannin, and gall tannin mixed with iron sulfate, gum Arabic and water, produces an durable and indelible ink.
Leonardo da Vinci, J.S. Bach, Rembrandt and van Gogh all used iron gall ink in their work.
The tannic acid in galls also lends itself to tanning hides and making dyes. Oak galls, for example, have long been used by Native Americans to produce a jet black dye for basket making.
In Great Britain, Rose Bedeguar galls historically had a wide range of medicinal uses. A dried form of the gall was given to babies to relieve colic. The powder was also used as a diuretic and a dental aid. Long before Rogaine, a paste made of Rose Bedeguar gall and honey was painted on the scalp to prevent hair loss. For health issues at the other end, the oak marble gall was ground into a powder and mixed with hog's lard, then applied to hemorrhoids. Rose Bedeguar galls were also used as a sleep aid. Place a gall under your pillow and enjoy peaceful night's sleep.
There's no shortage of superstition and folklore associated with galls. For example, if you open an oak apple gall and find a spider inside, your crops will be ruined in the upcoming year and you will suffer food shortages. If the opened gall has nothing in it, there will be disease and pestilence in the year to come. If, however, a fly is found inside the gall, you can look forward to a pleasantly uneventful year.
And of course, someone somewhere must have experimented with edible properties of galls. Yes, some people do eat the larvae inside galls as survival food. In a pinch, however, I'd be more inclined to use the larvae as bait for fish, and then eat the fish to quell my hunger.
The ecology, form, diversity, and uses of galls make these fascinating structures. Check them out. Take a walk in your local forest preserve this fall and keep your eyes open for galls of all shapes and sizes among the splendor of fall colors.
• Naturalist Valerie Blaine can be found in the woods and weeds searching for galls and other oddities of nature. You can contact her at blainevalerie@kaneforest.com.