While visiting my sister’s family, we took a stroll (as I often ask to) around the landscape. They’ve owned their home for a little over a year now. The variety of previously installed trees and plants are plentiful, though placement has at times left us scratching our heads. One of the trees on the property is a River Birch (Betula nigra). As we approached the tree, I noticed something odd about the leaves.

Why are my river birch leaves covered in pink velvet?

A lot of people would immediately assume the tree is sick, buy a pesticide, and douse the tree in hopes of saving it. Mature trees cost quite a pretty penny to replace in a landscape. However, the more economical and ecologically-safe way to handle the situation is to first identify what is going on with the plant. It doesn’t make much sense to take a round of steriods if all you have is a chipped fingernail, right?

Even though my sister wasn’t sure if the pink areas meant the birch tree was diseased, she was on the right track by asking questions. What was this pink fuzz? What causes it? Was there any need to worry about the tree’s health? So began our sleuthing…

Clues to Determine Plant Disease

First we would need to identify the type of tree we were examining, which we already knew. The River Birch is a native to the Eastern United States, loves acidic soils, is at home in wet ground, and is one of the few heat-tolerant birches. It also has a beautiful, self-exfoliating bark which makes it a highly sought after landscape tree.

Next, we pulled some branches down toward us to take a closer look at the top side of the river birch’s leaves. The surface of the birch leaves were covered in what appeared to be a pink fuzz. The leaves were not chewed up and there weren’t visible insects present on the top or bottom of the leaves.

Next, it was to The Internets to find the culprit! Usually, university websites are most reliable when trying to identify plant pests and diseases. With the tree’s name and a description of it’s affliction, I was able to solve the mystery of the pink fuzz and what caused it.

Erineum Gall

According to the University of Minnesota Extension site, “galls are formed by insect/mite feeding or egg-laying activity.” Galls are plant cells that have increased in size or number due to the insect or mite. Further reading categorizes galls into leaf galls, stem and twig galls, and bud / flower galls. The pink fuzz is a type of leaf gall, specifically a Erineum Gall as those are characterized by “(hairy felt-like growths) on the upper or lower leaf surface.”

What Causes Erineum Galls on River Birch?

The Mississippi State University Extension site points out that galls are host-specific. More digging around found articles on the University of Minnesota and the Wisconsin Department of Agriculture site identifying eriophyid mites as the cause of erineum galls on river birch. The Ohio State University Extension site goes further to identify the mite A. brevitarsus as the eriophyid mite that “generates pinkish-red erineum patches on the upper leaf surface of birch leaves.” These tiny mites overwinter on the tree and begin feeding on the plant tissue in the spring when the tree leafs out.

Are eriphyid mites harmful to the river birch? All state extensions sites I referenced had the same answer; “no.” The mites do not effect the overall health of the river birch and often the damage is purely cosmetic.

Pest Control for Eriophyid Mites

When I find a pest or disease on a plant to be purely cosmetic, most of the time I just let it run its course. According to the Missouri Botanical Garden site, the use of a miticide could kill predator mites as well and worsen the outbreak. Many chemical treatments do not work because precise timing of applications is needed before mite activity begins. By the time the erineum galls are visible on birch trees, there is no effective treatment (chemical or otherwise) to control the mites since they are protected by the galls.

If the landscape owner feels it is absolutely necessary to try to control the eriophyid mites, The University of Minnesota Extension site recommends  applying a horticultural oil at bud break right before mite activity begins.

Things I thought I would never say during my life: “It was quite interesting to read fifty-three pages of course material about turf and then attend a class solely focused on the subject.”

I have spent the past two weeks making it clear if I fell asleep in any of my Master Gardener classes, it would be during the class about turf. A lawn to me is prime perennial real estate going to waste. The Lot is quite tiny, a fact I struggle with each time I want to bring a new plant home with me. We don’t have kids; we don’t play golf. The four-footed garden help prefer to imagine themselves as wild jungle cats while stalking among the shrubs and other various plants. Why would we want to waste space with grass?

However, even though it did not persuade me to yank my perennials in favor of a well-manicured lawn, the inner workings of the grass plants and the responsible ways to maintain one were pretty cool to learn about. Here are just a few things I learned.

Don’t Scalp Your Lawn

One of the keys to a great-looking turf is to keep the height of the mower set between 3-4″ high. That’s right…a short lawn can starve, get sick, loose to weeds, and generally stress out. A taller height allows grass plants to photosynthesize more carbs to build stronger root systems. It also creates a plant canopy to shade out the weeds that are trying to germinate. Short blade height also allows the hot sun to burn the grass plant’s crown. Ouch. The instructor had a great suggestion on how to embrace this new approach to mowing height.

Set your mower to the highest height, take it to a local auto shop, and have them weld the mower deck into place.

Buyer Beware

I’ve noticed throughout the Master Gardener classes that the fertilizer and pesticide companies LOVE an un-educated and/or lazy homeowner. There are a lot of resources available to a homeowner for common lawn problems like lack of nutrients in the soil or controlling pests like grubs. For example, when Spring finally arrives in MI, the box stores have huge end-caps advertising grub control products for the lawn. Spring is a horrible time to apply an insecticide to control grubs. The insect is not in the right stage of it’s life-cycle to be sufficiently curbed by pesticides.

Before randomly throwing money at a box store (they will take your $$$ without argument) and spraying the lawn with chemicals, check out a site like MSU Turfgrass Science and get informed. There are some handy lawn care product reviews on the site as well.

Can’t Make Chicken Soup Outta Chicken Sh*t

I know neither chickens nor soup have anything to do with turf here, but I am going somewhere with this. The quality of soil in the yard is the foundation of all things green and beautiful for a homeowner. If the soil is poor, more than likely the lawn will struggle. Before blaming a pest or disease, make sure your soil has what it takes to support the grass. A nutrient deficiency is just a likely to make a lawn look terrible. Most state extensions offices offer a soil test for residents to figure out what exactly is going on with your soil. The MSU Extensions Office provides the service to Michigan dwellers here.

Screw the Joneses

Your lawn does not need to be a golf course. Period. I have friends who live in a wealthier subdivision and they have fully embraced this concept. My chest swells a bit with pride each time I pull up to their home during the summer and observer their naturally dormant lawn. I can’t imagine how much their neighbors must spend in blood-pressure control meds.

It is completely up to the homeowner to what level they maintain the lawn. If you want to imagine yourself on a putting green while walking across the yard, you can do so. Just be smart about the resources expended to accomplish this… Inform Yo-Self. If you do not want to spend the money and resources and rather just make sure the grass plants survive a season (they’ll bounce back in the Fall anyway, right?), that is okay also.