Botrytis On Gladiolus Plants: How To Control Gladiolus Botrytis Blight


By: Mary Ellen Ellis

Related to irises and sometimes called ‘sword lily’ for its spikes of blooms, gladiolus is a pretty, striking perennial flower that brightens many beds. Unfortunately, there are some diseases that can strike these plants and destroy them for a season.

Gladiolus botrytis diseases are not uncommon, so knowing the signs and how to manage them is vital to your plants.

Identifying Botrytis on Gladiolus

Botrytis is a fungal infection caused by Botrytis gladiolorum. The infection is also called neck rot or corm disease. The fungus infects and damages leaf, flower, and corm tissue. The corm is the tuber-like storage organ of the roots of the plant.

Above the soil you’ll probably first see glads with botrytis by noticing spots on the leaves and stems. Leaf spots caused by botrytis may be small, round, and rusty red. They may be yellow to brown or the spots can be larger, more oval in shape, and with a red brown margin. Look also for rot at the neck of the plant stem, just above the soil.

The flowers will first show signs of infection with water-soaked spots on the petals. Decline is rapid in the flowers and these spots will quickly transform into a slimy, moist mess with grayish fungal growth.

The corm, which is under the soil, will rot with botrytis infection. It will become soft and spongy and grow black sclerotia, the body of the fungus.

How to Control Gladiolus Botrytis Blight

Botrytis blight affects gladiolus around the world, wherever it is cultivated. When planting this flower, use corms that have been pre-treated to prevent getting the disease in your soil.

If you do have the disease in your garden, it will spread through infected corms and decayed plant matter. Destroy all affected plant material.

If you haven’t been able to prevent gladiolus botrytis diseases in your plants, treating gladiolus botrytis requires the use of fungicides. Your local extension office can help you choose and learn how to use the right fungicide. Generally, botrytis can be managed with chlorothalonil, iprodione, thiophanate-methyl, and mancozeb.

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Treating Gladiolus Botrytis Blight - What To Do For Glads With Botrytis - garden

How To Treat Botrytis and Mildew

BOTRYTIS (Grey Mould)
A very common disease for many plants and vegetables. Botrytis is first noticeable as brown spots, which are followed by a furry grey mould. The cause of the disease is too much dampness in cool conditions - growing plants in over-fertile conditions also encourages botrytis.

How to Treat Botrytis
Remove the conditions which caused the disease in the first place. Avoid over-watering and ensure that the plant or seedling has plenty of air circulating - if the plant is congested with leafy growth, prune away some of the growth (especially in the centre of the plant) to permit air to circulate. Reduce the amount of fertiliser being applied.

All infected growth should be removed and burned - do not put it on the compost heap. Where the garden pest botrytis persists, spray with Copper Fungicide (Bordeaux mixture) which is safer for you and garden life than most other chemical sprays available in garden centres.

MILDEW (Powdery and Downy Mildew)
The symptoms are light grey powdery patches on the leaves, shoots and flowers, normally appearing in spring. The flowers will turn a creamy yellow colour and will not develop correctly.

Powdery mildew remains on the surface of the plant downy mildew will get right into the plant, eventually killing it. The causes of the disease are exactly as for Botrytis - cool and over-damp conditions.

How To Treat Mildew
Treat exactly as for Botrytis above.


Ground cover diseases

Ground covers often make our jobs as gardeners easier by preventing weeds, holding soil in place, and helping to moderate soil temperature extremes. Ground covers, however, are not maintenance free. Like all plants, they can be susceptible to disease problems. In fact, ground covers are frequently used where conditions are favorable for disease.

  • They grow low to the ground and fairly close to each other, which can limit air circulation.
  • Their leaves are often wet, favoring fungal infections. This is the result of frequent rains, overhead watering, crowded plantings, and heavy shade.
  • They are often grown in less than optimal conditions where other plants won’t grow. Plants grown in a stressful environment are more prone to disease.
  • Fallen leaves from overhead trees are often left on top of ground covers. This promotes wetness and provides a favorable environment for disease to grow and overwinter.

Some of the more common diseases of ground covers are described below.

VOLUTELLA STEM BLIGHT OF PACHYSANDRA

Ornamental ground cover Japanese pachysandra (Pachysandra terminalis) is susceptible to a serious, destructive stem and leaf blight called Volutella blight. The native Allegheny pachysandra (Pachysandra procumbens) is reported to be more tolerant of the disease.

Symptoms

This disease, caused bythe fungus Volutella pachysandricola, will cause leaf blight and stem cankers on most pachysandra species. Symptoms, first noticed in early spring as brown to tan leaf spots, can be confused with winter desiccation. The spots will enlarge and may eventually cover the entire leaf. Concentric circles form within the spots. Leaves eventually turn yellow and fall off the plant. Stems turn dark and die. During extended wet periods, orangish-pink fungal spore masses may be visible. Eventually, large patches of the ground cover may become infected and die.

Conditions Conducive to Disease

Volutella is an opportunistic pathogen. It can infect a plant any time during the growing season but is more common during periods of rainy weather. Infections tend to diminish as the weather becomes drier in the summer, but the high humidity created by heavily mulched beds can promote the blight. Stresses, such as overcrowding, winter injury, or shearing, also may increase susceptibility to stem blight. Older and injured plant parts of Japanese pachysandra are more susceptible to the disease. Consider whether the site is one in which pachysandra can thrive. Pachysandra prefers filtered sun to full shade more than full sun conditions, and will be stressed by the latter and more susceptible to blight.

MANAGEMENT

See cultural control recommendations at the end of this leaflet.

Contact the Plant Clinic (630-719-2424 or [email protected]) for current recommendations.

PHOMA STEM BLIGHT OF VINCA (PERIWINKLE)

Stem blight is a serious disease of periwinkle (Vinca minor), also known as myrtle.

Symptoms

Stem blight is caused by Phoma exigua var. exigua, a fungus that can live indefinitely in moist soil and plant debris. Dark brown to black lesions appear on stems of overwintering runners at the ground line. These lesions girdle the stem. Soon after growth begins in spring, the new stems may also wilt, turn dark brown to black, and die. In just a few weeks, entire clumps of plants may die. The fungus frequently spreads from the stem lesions onto the leaf petioles and the base of the leaf. This is a difficult disease to control once plants are infected, so prevention is important. Rhizoctonia blight appears similar to Phoma but no fruiting bodies are produced on the lesions. Be sure of which disease you have to increase your likelihood of growing healthy plants.

Conditions Conducive to Disease

Phoma blight is more common in cool, wet weather. Thinning overcrowded plants to improve air circulation and drying is helpful.

MANAGEMENT

  • See cultural control at the end of this leaflet
  • Some cultivars are more resistant than others, although little has been published on this. For example, Vinca ‘Darts Blue’ is reported to resist the blight.

Contact the Plant Clinic (630-719-2424 or [email protected]) for current recommendations.

BACTERIAL OR FUNGAL LEAF SPOTS OF ENGLISH IVY

Although over forty pathogens cause leafspots on the popular ground cover English ivy (Hedera helix), the two most common foliar diseases are caused by a bacterium and a fungus. If you are using chemical control, it is important to determine which of the two pathogens are the cause because chemicals used for bacterial leaf spots are different from those used to treat fungal leaf spots. Fortunately, it is not difficult to determine if an ivy leaf spot is bacterial or funal.

Symptoms

Bacterial leaf spot, caused by the bacterium Xanthomonas campestris pathovar hederae, is more common in warm weather. Initially, the leaf spots look light green and “water-soaked”. Later, the spots appear dark and greasy-looking and may have definite margins and a yellow halo visible when the leaf is lifted up to light. Often the spots crack with age and bacterial ooze may emerge from lesions when the conditions are wet and warm. Severe infection can cause leaf distortion, blight, and premature defoliation. Bacteria can also cause black cankers on stems, killing them. Fungal leaf spots are tan to brown and may be irregularly shaped. Often they produce concentric rings as the spot enlarges. You may be able to see fruiting bodies that look like black pepper within a spot. If fruiting bodies aren’t present, place the leaves in a plastic bag with a moist paper towel overnight. If the leaf spot is fungal, fruiting bodies should appear in the spot the next day. Fungal leaf spots do not cause stem cankers.

Conditions Conducive to These Diseases

These diseases require a wet leaf surface for an extended period of time, often more than 24 hours. For fungi, this allows spores to swell and germinate, and penetrate the leaf surface. Bacteria will multiply and enter through leaf stomata (a natural surface opening) or colonize in plant wounds. Leaf spot diseases may be more severe if leaves are infected when they first emerge in the spring. If the weather is dry during bud break, infection may occur later during wet weather after the leaves have expanded. Late infections are unsightly but rarely harm the plant.

MANAGEMENT

See the cultural control at the end of this leaflet.

Contact the Plant Clinic (630-719-2424 or [email protected]) for current recommendations.

BOTRYTIS BLIGHT OR GRAY MOLD

Botrytis blight is a common fungal disease of many plants, including vinca, pachysandra, and ivy, as well as hundreds of trees and shrubs. There are several species of the fungus Botrytis that can cause blights. The most common is Botrytis cinerea.

Symptoms

Botrytis can affect leaves, stems, flowers and flower buds, seeds, seedlings, and bulbs. The fungus often colonizes dead plant parts first, and then spreads into living ones. Infected plant parts look blighted or dark with lots of gray fuzz in the infected area. This fuzz is actually fungal mycelia. Clouds of air-borne spores may be released from the mycelia in wet weather. Tiny, black specks may be visible in the gray fuzz. These are sclerotia, which are the fungal structures in which the disease overwinters. The fungus also overwinters in diseased plants.

Conditions Conducive to Disease

This disease is most prevalent in cool (55-65 degrees F), humid to rainy conditions. It attacks plants that are weakened by poor nutrition, low light intensity, low temperatures, or senescence (aging).

MANAGEMENT

See the cultural control at the end of this leaflet.

Contact the Plant Clinic (630-719-2424 or [email protected]) for current recommendations.

CULTURAL CONTROL FOR GROUND COVER DISEASES

  • Purchase healthy plants that are free of disease.
  • Purchase species or cultivars that are considered disease tolerant or resistant.
  • Select plants that are right for the site conditions. Plants growing in less than optimal conditions are more likely to be stressed and more susceptible to infection.
  • Plants should be watered during dry periods by using drip irrigation and/or by watering early in the day to allow foliage to dry out. In established beds, avoid overhead watering or watering in the evening.
  • Avoid working with plants when they are wet to prevent the spread of disease.
  • Remove and discard diseased leaves and plants immediately to keep infections from spreading to healthy plants.
  • Clean up fallen leaves and other debris that has accumulated on top of ground covers.
  • Thin, prune, and divide overcrowded plants in early spring, when weather is dry, to improve air circulation.
  • Avoid over-fertilization, which causes dense, succulent growth susceptible to infection.


Refer to the Illinois Urban Pest Management Handbook (University of Illinois Cooperative Extension Service) for a complete listing of chemical recommendations. Use pesticides safely and wisely read and follow label directions.

The pesticide information presented in this publication is current with federal and state regulations. The user is responsible for determining that the intended use is consistent with the label of the product being used.

The information given here is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement made by The Morton Arboretum.


Cultural Prevention

To prevent the drooping of flowers as a result of wind damage or weak growth, stake your gladioli or provide other structural support at planting time to promote upright growth from the beginning and to avoid root damage, suggests the University of Minnesota Extension Service. For cultural prevention of botrytis blight, irrigate soil directly through a method such as drip irrigation overhead sprinkling creates standing water, which encourages the proliferation of fungi and subsequent disease development and droop.


Reader Comments

Botritis

Submitted by jim on October 10, 2018 - 6:22pm

all plants in my greenhouse are finished but whats left is heavily infested with botritis. when i remove the plants, spores are going to fill the air. the soil will be covered with spores. my question is can i use that soil again? can i take the soil outside and add alot of nitrogen to start it composting?

Botrytis Spores

Submitted by The Editors on October 12, 2018 - 2:54pm

Botrytis spores can be cooked away in a compost pile, but only if the pile reaches upwards of 131°F (55°C) and stays at that temperature for several days. That being said, we wouldn’t recommend using the soil in your greenhouse again, just in case the composting didn’t do the job completely.

Compost

Submitted by jim on October 12, 2018 - 4:22pm

thanks for the recommendation. what do you think i can add to the 5 yards of soil to get it hot enough to kill the botritis spores.
i'm thinking, cottonseed meal & straw. i want to be organic & economical.

Black rot on concord grapes

Submitted by ANN on August 17, 2016 - 10:03am

is there a natural remedy to correct this problem without using chemical sprays?

Natural Remedies for Gray Mold

Submitted by The Editors on August 17, 2016 - 11:49am

Unfortunately, it can be difficult to get rid of gray mold without chemical sprays. We would recommend following our tips like destroying all plants that are infected and making sure that your plants are not in an overly moist environment. The article provides some natural and easy prevention methods that might be able to keep you from having to use a chemical spray.

Hydrangea with shiny white patches on the leaves.

Submitted by Kathee on August 7, 2016 - 8:42pm

I just planted some hydrangea. Two days later when I went to water them they have large shiny white patches on most of the leaves. What is the problem?

Powdery Mildew on Hydrangeas

Submitted by The Editors on August 8, 2016 - 2:13pm

It appears that the problem might be powdery mildew. To find out how to prevent and control this fungal disease, go to our powdery mildew page.

I have a petunia in a hanging

Submitted by Patty Heiney on July 19, 2015 - 7:38pm

I have a petunia in a hanging pot and I noticed it has black spots on leaves and around small blooms. I don't know if they are bugs of some kind also found a small green worm or maggot on another bloom. Any suggestions on what to put on my plant? Some of my plant leaf ends are a pale light green is this not enough water?

Black specs might be

Submitted by The Editors on July 22, 2015 - 12:10pm

Black specs might be "frass". caterpillar poop. You may have a worm eating your plants. Blast the leaves with insecticide spray.

I have a hydrangea plant has

Submitted by Amy Kramarsic on July 19, 2015 - 6:04pm

I have a hydrangea plant has brown leaves and are falling off.We think it may have over watered.Is there any way I can save plant?

Are the hydrangea leaves

Submitted by The Editors on July 22, 2015 - 12:14pm

Are the hydrangea leaves turning brown around the edges? Usually, this is a moisture issue. Sometimes, the plant can be root-bound, too.
Gently dig the plants early in the morning to check for both conditions. If needed, lightly loosen the roots with your hand. You can also soak the root ball in water until it's moistened through. Make sure you maintain uniform moisture for your hydrangeas.
Location can also be an issue. If they're getting sun burnt, they'd do better with light shade.

I bought a spider plant all

Submitted by ruthe Fitzsimmons on March 9, 2015 - 8:10pm

I bought a spider plant all of the leaves are yellow and the tips are black and appear to be bent like an edge.
Could you please help?

It sounds like your plant may

Submitted by The Editors on March 10, 2015 - 10:00am

It sounds like your plant may be getting too much sun. Move it to a cooler spot in the house be sure it is not close to heat vents or on top of the television.

I have peonies that seem to

Submitted by Twiggs1221 on September 10, 2014 - 11:00pm

I have peonies that seem to have this gray mold on the leaves. It hasn't turned brown or wilted the leaves, but I've noticed that my hydrangea that is next to it doesn't look too good. I have 3 others in my gardens and they all look great still. Could whatever is on the peonies have affected my hydrangea too? Its not as green and lush as it should be and the edges of the leaves look like their browning. I live in zone 7 and my peonies are well passed bloomed. I usually wait til fall to cut the foliage down. Should I have cut that down sooner? And do you think I should move the peony because it is rather close to the hydrangea? When I put the hydrangea there it wasn't as big as it is now.

It's probably powdery mildew

Submitted by The Editors on September 11, 2014 - 11:53am

It's probably powdery mildew from humid conditions. It isn't pretty but it won't hurt the peony this late in the year. Cut it back in the fall and dispose of the leaves. Make sure your peony has good air circulation next year. It may be a good idea to move it away from the hydrangea. Go to our peony page for more information. www.almanac.com/plant/peonies

I have a question about my

Submitted by Sande Sanders on July 26, 2014 - 1:01am

I have a question about my garden and I think it is probably related to this article about gray mold. I recently moved to a northern California coastal town. Long growing season, very temperate climate. I'm living in my RV and am surrounded by asphalt, so I container garden, allot. I'm trying to keep the pots wet enough so that the plants don't wilt from the heat, but its humid here.
My sage plants turn yellow and get brown spots. My squash gets spots, turn brown and die. The gray webbing takes over. yuck,but the plant keeps trying. I have tomatoes near the squash, one looks like it rotted from too much water, but I don't water until the top few inches are dry. That's every other day here.
Any suggestions? I thought the plants were getting sunburned, maybe that's the damaged entry point for the gray mold. Some one suggested shade cloth. But doesn't that seem weird with tomatoes?

Vegetables and herbs can

Submitted by The Editors on July 28, 2014 - 11:02am

Vegetables and herbs can suffer from various problems due to high humidity, high heat, too much/too little water, etc. Too much water can cause sage leaves to yellow and form brown spots, but so can high temperatuers, etc. Sometimes squash gets downy mildew, powdery mildew, or white mold. Tomatoes can also get white mold, powdery mildew, root rot, etc. For some disease information, see:
http://www.ipm.ucdavis.edu/PMG.
http://www.ipm.ucdavis.edu/PMG.
http://vegetablemdonline.ppath.
In general, make sure not to waterlog the soil, and check the drainage at the bottom of the containers--be sure the drainage hole(s) are not blocked. Temperatures might get very hot if your containers are on asphalt, so a shade cloth during hot afternoons might be helpful, or positioning them to get partial shade in the afternoon. You can also add a little mulch on the soil surface--but keep the mulch from directly contacting the main stem of the plant, in case the humid air might encourage disease. Avoid overhead watering, which can encourage disease--water the plants at the base, or use self-watering containers.
If you could set up a fan to blow gently on the plants for a few hours each day, that might help to avoid diseases in humid weather. The more (gentle) air circulation, the better.

Some of my gladiola's florets

Submitted by jamil on February 2, 2014 - 2:05am

Some of my gladiola's florets did not open/ bloom on the top found them empty from indside. Is it a disece or under fed? Thanx.

It sounds like your gladiolus

Submitted by The Editors on February 6, 2014 - 4:43pm

It sounds like your gladiolus may have had thrips. They feed on the shoots and flowers.


Watch the video: How To Propagate Gladiolus Easy tips u0026 Gladiolus Updates


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