Concerns about oak trees have been common this spring. Careful observers have noticed that some of the leaves on white oak trees appear more brown than green, especially the leaves on the lower branches. Some of these leaves have even curled and fallen to the ground. The question on everyone’s mind is “Is this a serious condition or something superficial?”
Say the word “fungus” and most people think of negative things—moldy bread, deadly toadstools, plant diseases in the garden or nasty skin infections. Although many fungi can be harmful to people, animals and plants, the vast majority are actually essential to the functioning of the ecosystem. These helpful fungi are the overlooked, “unsung heroes” of the natural world.
Homeowners are reporting green or brown clusters hanging from the trees that look like a cocklebur. These clusters are caused by an eriophyid mite, and the damage is commonly called the ash staminate flower gall.
Sooty blotch and flyspeck may be as old as apples themselves. Drawings of apple varieties from the 1820s clearly show sooty blotch on every fruit. It wasn’t until sprayed-on pesticides, such as lime sulfur and lead arsenate, became popular around 1900 that consumers began to expect to buy apples without a heavy coating of sooty blotch and flyspeck. The cosmetically perfect apples found in today’s supermarkets weren’t common until the middle of the 20th century, when more effective organic fungicides appeared.
Willows and poplars are common trees for use in windbreaks or privacy screens because they grow very fast, providing effective screening within a few years. One of the most popular willows is the Austree, a hybrid willow (a cross of white willow and corkscrew willow) developed in New Zealand. However, many people are dismayed when these beautiful screens start declining and dying after a dozen or years, or even sooner. These fast-growing trees exemplify the saying, “live fast, die young” because, despite their fast growth, they are highly susceptible to several lethal diseases.
A walk through the forest at this time of year may lead to the discovery of what appear at first glance to be giant marshmallows. A closer investigation reveals that the spheres are composed of a soft spongy material – rather than a soft sticky material. These objects are puffballs, produced by certain soil-dwelling fungi. There are a number of different species of fungi that form puffballs and they can be found growing on the ground in forests, pastures and lawns.
The first “side” of the triangle is so obvious it may be overlooked. In order to have a plant disease, you must have a plant. More specifically, you need a susceptible plant, one that is able to get a particular disease. Each plant species is prone to a unique set of maladies. Crabapples and oaks get different diseases. Within a species, plant varieties differ in their susceptibility to various diseases. For example, some crabapple cultivars are decimated by apple scab while others are unaffected. The overall health and vigor of an individual plant also affects its susceptibility to disease.
Fungi and molds are popping up and out in Iowa lawns and gardens thanks to cool, wet conditions the past few weeks. Horticulturists with Iowa State University Extension and Outreach tell gardeners how to identify and manage some of the more common ones.
The Iowa State University Plant and Insect Diagnostic Clinic can help Iowans identify the mushrooms growing in their backyards and elsewhere, but cannot say whether they’re safe to eat. Multiple factors may contribute to wild fungi being potentially poisonous, most of which are beyond the control of the experts who identify the specimens brought into the clinic.