diseases affecting English laurels

I have some laurel bushes that are developing black or
dark brown leaves. It starts at the top and then works down.
Trimming them off seems to help but then another bush develops the
problem. I want to take care of this before it gets out of control.
A neighbor had an entire laurel die–it was probably 15 feet tall.

While I cannot diagnose a plant problem via e-mail,
it might be a bacterial or fungal problem, or an environmental
disorder. I am assuming your laurels are English laurels (Prunus
laurocerasus), not Mountain laurels (Kalmia). According to the
Oregon State University Extension’s Plant Disease database, English
laurel can suffer from leaf spots and shothole. Excerpt:

Cause: Shothole symptoms are commonly observed on Prunus sp. and
can be caused by a variety of factors. The bacterium Pseudomonas
syringae pv. syringae and several fungi including Cercospora sp.,
Blumeriella sp., and Wilsonomyces carpophilum (Coryneum blight) can
cause leaf spots and shothole on cherry laurel (English laurel,
Otto Luyken, or ‘Zabeliana’). Copper spray injury and boron
toxicity can also cause leaf spotting and shothole. When symptoms
are advanced, it is not possible to identify the cause
specifically.

Cherry laurels (English laurel, Otto Luyken, or ‘Zabeliana’), P.
laurocerasus and sometimes other Prunus sp. including cherry and
plum, commonly show shothole symptoms resulting from cultural or
environmental stress. Research has failed to identify what specific
stress is responsible. Both container- and field-grown laurel can
develop symptoms.

Symptoms: Necrotic leaf spots with circular to irregular margins.
Bacterial spots are brown surrounded by a reddish border with a
yellow halo. Abscission layers develop around necrotic leaf spots
causing the injured tissue to drop away, leaving holes and tattered
areas in the leaf (as if someone fired a shotgun at the leaf-thus
the name shothole). After tissues drop, most often it is difficult
to determine specifically what caused the initial injury.
Observations of early symptom development, signs, and symptoms on
other areas of the plant may help make an accurate diagnosis. Note the holes in the leaves.

Cultural control: No management practices have been shown to help
reduce physiological shothole. For disease-induced shothole, try
the following cultural practices.

Avoid overhead irrigation.

Remove and destroy fallen leaves.

Do not plant near other flowering or fruiting Prunus sp.

If the problem is shothole, this is usually an environmental
disorder, and infected parts of the plant should be removed and
destroyed.

Here is more information from U.C. Davis Integrated Pest Management on bacterial blight, which in laurels
usually affects only the leaves.

If you want to be sure of what the problem is, I suggest
bringing samples of the affected leaves to one of the Master
Gardener Clinics in our area.

managing mummy berry on blueberries

We have 5 acres that are covered in 50-year-old fir and cedar forest,
with lots of salal and evergreen huckleberry. The huckleberries have
what looks like mummy berries that I have seen in photographs of
blueberries before. They have a dry grey peeling that feels like old
garlic skin with a very hard brown inside. There doesn’t appear to be
any problem with the foliage. These bushes are naturally growing, and
are all over through the property. Mulching and cultivation would be
nearly impossible on this scale, and I’d really prefer not to spray if
possible. Can you suggest a safe method of control that would be
possible on this large scale? Or is this something that nature will take
care of on its own? Or do we even need to worry about it since we don’t
harvest the berries? I can live with a few shriveled berries. I just
don’t want it to spread wildly or kill off half of our underbrush.

If mummy berry is what you are seeing (and it does sound like it), it is
caused by a fungus which overwinters in the fallen berries, so anything
you can do to collect them might help. The following, from Ohio State
University Extension, describes the life cycle of this fungal problem.

The Organic Gardener’s Handbook of Natural Insect and Disease Control by
Barbara Ellis (Rodale, 1996) recommends removing the berries and in
spring, cultivating around the bushes to bury any fallen mummies, or
adding mulch to cover fungal spores.

Beyond the good hygiene of removing the fallen fruit, there may be a
chance that wettable sulfur spray might help, as described in this information from McGill University. Excerpt:

“Clean cultivation can reduce the incidence of mummy berry disease. This
practice destroys the fallen mummified fruit, which harbors the inoculum
for the next season’s infection. Wettable sulfur sprays have also been
effective in reducing mummy berry infection. In New Jersey, researchers
used three sprays roughly one week apart with the first spray timed for
leaf emergence in the spring.”

However, I found Ohio State University contradicting this information,
indicating that organic fungicides such as sulfur and copper were
ineffective against mummy berry.

Here is additional information from National Sustainable Agriculture
Information Service. Excerpt:

This fungus overwinters in mummified berries that have fallen to the
ground. Sod or moss directly under the plant will contribute to spore
production. To control this fungus, remove infested fruit (“mummies”)
from the plant, rake and burn mummified berries, or cover the fallen
berries with at least two inches of mulch. Cultivation during moist
spring weather will destroy the spore-forming bodies. Strategies that
lead to early pollination of newly open flowers may be useful in managing
mummy berry disease in the field, since studies show that newly opened
flowers are the most susceptible to infection and that fruit disease
incidence is reduced if pollination occurs at least one day before
infection.(Ngugi et al., 2002)

The fungus survives the winter on dead twigs and in organic matter in the
soil. The disease is more severe when excessive nitrogen has been used,
where air circulation is poor, or when frost has injured blossoms.
Varieties possessing tight fruit clusters are particularly susceptible to
this disease. Remove dead berries, debris, and mulch from infected plants
during the winter and compost or destroy it. Replace with new mulch, and
do not place mulch against the trunk of the plant.

I’m afraid there is not an easy solution for such a large expanse of
huckleberries. Then again, if you are not concerned about harvesting the
fruit, then you can probably just let it be. Since the fungus seems to be
a problem primarily for plants in the blueberry family, I do not imagine
it will harm other plants on your property.

yellow houseplant mushroom called Leucoprinus

I have a potted plant with a fungus growing in the soil. It
is bright neon yellow and grows like a mushroom, but with no cap on top.
The plant is in the basement near a window. The soil is damp and I’ve
avoided watering for awhile to let it dry out. What do you think the
growth is, how to get rid of it, and will it be harmful to my plant? I
keep plucking them, but they grow back.

I have had questions about the yellow houseplant mushroom before, and I
am guessing you are seeing the same thing. It is called Leucoprinus
birnbaumii.

Michael Kuo’s website, MushroomExpert.com has information about Leucoprinus. Excerpt:

“This little yellow mushroom and its close relatives are the subject of
many frantic e-mails to MushroomExpert.Com, since it has a tendency to
pop up unexpectedly in people’s flower pots–even indoors! The brightness
of its yellowness exhibits some rebelliousness, but it often creates a
striking contrast to the green houseplants that surround it.

“Leucocoprinus birnbaumii won’t hurt you, unless you eat it. It won’t hurt
your plant. It won’t hurt your pets or your children, unless they eat it.
There is no getting rid of it, short of replacing all the soil in your
planter (and even then it might reappear). Since it makes such a
beautiful addition to your household flora, I recommend learning to love
it–and teaching your children to love it, too.

“You might also impart the idea that mushrooms are very, very cool–but
shouldn’t be eaten. Perhaps your child would like to become an awesome
and famous mycologist some day. I would love to encourage your child’s
interest in mushrooms by putting his or her drawing of Leucocoprinus
birnbaumii on this Web page (at least temporarily).

“Leucocoprinus birnbaumii is probably poisonous; do not eat it. Handling
it, however, won’t hurt you.”

diseases that affect peony plants

I planted some peony bulbs last year and they grew nicely until they reached about 10 inches high. One was in the ground, and the other is planted in a medium sized pot outside. The one in the ground is now dead, and the other one is not looking good. It gets dark spots on the leaves, and then the leaves die. Can you help?

Without additional details, it is difficult to say what may be wrong with your peonies. The Penn State Extension has information on different diseases that can affect peony plants. What you describe sounds somewhat like peony leaf blotch or measles, as shown in Iowa State University’s Plant Pathology webpage on peony diseases. Here is an excerpt:
“Peony leaf blotch is also known as measles or stem spot. Warm, humid weather provides optimal conditions for infection by the causal fungus, Cladosporium paeoniae.

The leaf spots are glossy and purplish-brown on the upper sides of leaves. On the lower sides, spots are chestnut-brown. Infection is generally more pronounced at the margins of outer leaves. Leaves may become slightly distorted as they continue growing.

Fungal infections on young stems first appear as elongated, reddish-brown streaks. As plant growth continues, infected tissue near the crown may darken and become depressed. Stems on the upper portion of the plant may show individual, raised spots.
To manage peony leaf blotch, cut the stems at ground level in the fall or early spring. Rake the area before new shoots appear. Fungicides are available to help control the disease, but must be used in combination with other management practices. Also, providing good air circulation and avoiding wetting the leaves when watering can help reduce disease severity.”

There are other possibilities, including peony blight, also known as Botrytis blight. The Royal Horticultural Society discusses this problem:
“Peonies collapse at soil level and the stem bases are covered in grey mould. In a severe attack the leaves are also affected and the plant may be killed or so badly weakened it fails to sprout again next spring. Infections also occur frequently behind the flower buds just before they open.

This is a disease that affects both herbaceous and tree peonies. It is caused by a fungus (Botrytis paeoniae) related to grey mould (Botrytis cinerea), which may also attack peonies in a similar way.

Wilt is encouraged by high humidity which builds up around dense clumps of peonies. Increase the circulation of air by thinning out overcrowded shoots. Also avoid over-feeding, especially with nitrogen-rich fertilisers, which encourages lush, disease-prone growth.

Cut out all infected stems well below soil level, as soon as you notice them. Don’t put infected material in the compost bin but burn it or put it in the dustbin, preferably in a sealed bag. If whole plants are badly affected lift and destroy them in their entirety along with the soil surrounding the roots. This total destruction is essential as the fungus can produce black resting bodies (sclerotia), which survive for long periods in the soil ready to re-infect new peonies.

There are no fungicides available to amateur gardeners at present.”

I recommend taking plant samples to your local county extension agent for diagnosis.