Gall on Virginia Pine

Wednesday afternoon, this sample of Virgina Pine came into the Master Gardener Info line. The gall on this branch is caused by a disease known as Pine-Oak Gall Rust. This fungal disease, caused by Cronartium quercuum, requires two different hosts to complete its life cycle. It lives part of its life-cycle on pines and part of its life-cycle on oaks.

Symptoms on pine include swollen areas on the branches, lumps or galls measuring up to 4 inches across, and slowed growth. Trunk galls on young trees may result in death or breakage of the trunk or branches at gall location. Galls on branches may girdle and kill tissue beyond the infection. Symptoms on oak leaves include small dark brown spots with yellow borders on the upper leaf surfaces, and reproductive structures develop on the underside of infected leaves.

In the spring, mature galls on the pine host release windblown spores, which infect expanding oak leaves. About one week after infection, orange spores are released from the underside of infected oak leaves, causing additional oak leaf infections.

The above photograph shows the orange spores produced by the pathogen and being released on the surface of the gall.

Control measures include removal of infected branches on pines to remove the source of inoculum (spores) available for infecting oak trees. No control measures are feasible on oak trees.

Entertaining Video form Utah State Extension

I got a great chuckle out of this video produced by Utah State University Extension. Take a few minutes and enjoy the hard work put into this video of "Gnome Control in the Garden".

No Spray Roses for Southeastern US

Black spot (Diplocarpon rosae, Marssonina rosae) is one of the most common and important diseases of roses throughout the world. Black spot will cause a general weakening of the plant so that progressively fewer and fewer blooms are formed if the disease is left unchecked. Spots are nearly circular with fringed or feathery margins and vary in size. Surrounding leaf tissue turns yellow before dropping. Bottom leaves are normally affected first. Conditions that favor the development are 75-85 degrees F, temperatures with relative humidity above 85%, overcrowding and reduced air flow.

Cercospora leafspot (Cercospora puderi, Cercospora rosicola) is characterized by the appearance of numerous tiny maroon to purple oval spots scattered randomly across the leaf surface. Later the center of the spot turns tan to gray in color while the margins remain maroon to dark purple. Heavily spotted leaves will turn yellow and prematurely shed. This infection can be easily confused with Blackspot. Same weather conditions that produce Blackspot will provide optimal growing conditions for Cercospora.

A homeowner may use a fungicide labeled for control of Blackspot to control both of these fungal infections. Fungicides, such as Daconil and Immunox, which are recommended as weekly treatments for blackspot control, should also provide good protection from Cercospora leaf spot when applied on the same schedule.

The University of Tennessee has been conducting a no-spray rose trial for the last two years. A total of 136 cultivars were evaluated for their resistance to black spot and cercospora leaf spot in 3 test locations across the state. Below you will find a listing of the most resistant cultivars of shrub roses. If you would like a full listing of rose cultivars tested, please contact me for a handout.

o Carefree Sunshine (Yellow)
o Hansa (Mauve)
o Homerun (Flame Red)
o Knockout (Cherry Red)
o Palmengarten Frankfurt (Mauve Pink)
o Pink Knockout (Pink)
o Wildberry Breeze (Mauve)

Information provided by Alan Windham, University of Tennessee Extension Service.
American Rose Society http://www.ars.org/

Devil's Dipstick

Many people enjoy feeding birds. They fill their feeders each day and birds showed up for the feast. Their yard provides food and cover for her birds. It’s interesting that we do the same thing for fungi. We mulch our landscape beds with bark mulch. Yet we seem surprised when fungi show up to feed on or live among the remnants of trees. What some view as unnatural is one of the most natural processes in nature. Take a walk in the woods after a rain and you’ll see a plethora of fungi growing on rotten logs and fallen branches. It’s been estimated that there are 400lbs/acre of fungal biomass in some woodland soils.

Most of our wood rotting fungi are basidiomycetes, capable of breaking down cellulose or lignin. Many fungi that we see on mulch are not feeding on wood. Indeed, most of the fungi encountered in mulch are not plant pathogens and are harmless to plants. Some of the more common fungi observed on mulch are slime molds, stinkhorns, bird’s nest fungi, and various higher fungi that produce a fruiting structure called a mushroom or toadstool.

Above is a photo of a stink horn. The fruiting body of this fungus is brightly colored, but you will probably smell it before you see it. One of the more common stink horns is Mutinus elegans, called the elegant stinkhorn or the “Devil’s Dipstick”. The smell of the elegant stink horn has been compared to rotting meat. It’s the smell that attracts insects which aid in spore dispersal.

Photo and Article taken from "Ornamental Pest and Disease Update - July 2007". Written by Alan Windham, UT Extension.

Slime Mold - "Dog Vomit"

Each year we know that with the summer comes a vast array of slime molds (also known as dog-vomit fungi) appearing in mulch. They appear in several sizes and colors with no definite shape.
I have watched those in my mulched landscape beds change on a daily basis from a bright yellow netting, to a tan powder, to a dark brown dried blob.
Slime molds get their nutrients from dead organic matter, such as mulch. Although slime molds may occasionally grow on plants such as turf, they do not harm plants.
Slime molds will eventually disappear on their own. If you want to speed this process, rake the mulch to promote air drying.