Fusarium Crown Rot Disease: Control Of Fusarium Crown Rot
By: Liz Baessler
Fusarium crown rot disease is a serious problem that can affect a wide range of plant species, both annual and perennial alike. It rots the roots and crown of a plant and can lead to wilting and discoloration on the stems and leaves. There is no chemical fusarium crown rot treatment, and it can cause stunted growth and even eventual death.
There are steps you can take toward fusarium crown rot control, however, that include prevention, isolation and sanitation. Keep reading to learn more about fusarium crown rot disease and fusarium crown rot treatment.
Fusarium Crown Rot Control
Many of the symptoms of fusarium crown rot disease take place, unfortunately, underground. There are, however, signs that affect the above-ground part of the plant, too.
The leaves may become wilted and take on a yellowed, scorched appearance. Also brown, dead lesions or streaks may appear on the lower part of the stem.
Usually, by the time fusarium is visible above ground, its spread is pretty extensive below ground. It can also be seen in bulbs that are shriveled or rotten. Never plant these bulbs – they may be harboring the fusarium fungus and planting them could introduce it to otherwise healthy soil.
Treating Fusarium Rot in Plants
Once fusarium is in the soil, it can live there for years. The best way to prevent it is to keep the soil well drained and to plant cultivars that are resistant to the disease.
If it has already appeared, the best method of treating fusarium rot is removing and destroying affected plants. You can sterilize soil by moistening it and laying down clear plastic sheeting. Leave the sheeting in place for four to six weeks during the summer – the intensified heat of the sun should kill the fungus living in the soil.
You can also leave an infected area unplanted for four years – without plants to grow on, the fungus will eventually die.
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How to Deal With Fusarium Wilt in Your Garden PlantsSteph Coelho
Steph is a certified Square Food Gardening Instructor who has been gardening for more than 10 years in Canada where the winters are long and cold, and the summers are unpredictable. She is a volunteer for her community's Incredible Edible project. In the past she created an educational gardening space for seniors and taught classes at a local community center where she created her own curriculum and activities. She participated in several local municipal garden days where she set up a booth to educate citizens about the joy of gardening.
Spotting yellowed, wilted leaves on your garden plants is a surefire way to ruin your day.
Yellow leaves can mean a whole bunch of things. You might have forgotten to water your plants. There may be a nutrient deficiency. Or maybe it’s a bit too hot for your plants to thrive.
Unfortunately, yellowed leaves may also be a sign of a disease like fusarium wilt.
How can you tell when a nasty fungus has overtaken your plant? How can you fix your sad-looking plant after it is infected by a pathogen? Read on to find out more about this plant disease.
10 Most Common Asparagus Diseases
1. Purple Spot
Purple spot is a disease that usually only affects asparagus plants, unlike many other diseases on this list that target plants of all kinds.
It’s pretty easy to diagnose. During particularly wet or windy weather, purple spots will develop on your spears. The good news is that the spots don’t affect the taste or texture of your asparagus spears, and they often disappear entirely during cooking.
The bad news is that, if you are trying to sell your spears or otherwise just care how they look, the purple spots will detract from their overall appearance.
Also, if left unattended, the spots can develop into full lesions and grow together into large blobs, ultimately killing affected tissue and defoliating the plants.
Most common in cool, damp weather, purple spots can be prevented by following good field sanitation. Cut back last year’s ferns and remove any plants affected by the disease.
Rust is one of the most common asparagus diseases. It presents several symptoms depending on the season.
It first rears its ugly head in the early spring or early summer, appearing as small, raised lesions that are generally light green.
Eventually, these turn a whiter or orange color and become more sunken in. You might not notice them at first, but as they progress, additional lesions will appear around the base of the stems.
Then, the namesake rust develops. This occurs as the weather warms later in the summer. The first set of lesions will burst, disseminating spores into the air and infecting other plants. You’ll know it’s rust for sure if you brush the asparagus ferns and come away with your hands covered in a reddish tinge.
The problem does not go away as the weather cools, with black overwintering spores being produced that can weaken the stems the following spring. It can cause the whole plant to die back.
The easiest way to prevent rust is to cut back the ferns as they die over the winter. Dispose of the infected pieces. Although crop rotation isn’t really possible with asparagus since it is a perennial plant, avoid planting new beds in the same general vicinity as the old ones. You may have to use a fungicide to kill existing spores.
Of course, fungal spores are more likely to infect plants when they are damp from rain or dew. Planting in a location that is sunny and somewhat breezy can help the plants dry out.
3. Fusarium Crown Rot
Fusarium crown root is generally caused by one of three species of Fusarium fungus: Fusarium oxysporum f. sp. asparagi, Fusarium proliferatum, and Fusarium moniliform.
This issue, also known simply as Fusarium disease, can cause yellowing, dry rot, wilting, and eventual plant death. It’s a soil-borne fungus that kills plants quickly after it infects them with red-brown lesions. It typically causes the roots to rot and die immediately, too.
Unfortunately, this disease is hard to prevent and get rid of. Crown rot can live in soil for a long period, spreading through infected air, soil, and seeds.
Plants that are stressed are more likely to be infected, so keeping up good cultural practices to avoid stressing your plants is essential. You should also work to improve drainage so that the soil does not remain soggy.
A simple way to prevent the disease is to keep the area around the asparagus beds free from weeds – these can harbor fungal spores and make it tough for you to get rid of the disease in the future.
Don’t harvest your asparagus plants continuously throughout the season, but let them rest periodically so that you don’t overstress them. Being consistent with fertilization and irrigation is also essential.
Blight, also known as Cercospora blight, is caused by Cercospora asparagi fungus. It causes gray or tan lesions to form on needles and small branches of plants, with each lesion surrounded by a red-brown border. These spores, like other fungal spores, are distributed by wind and rain.
As you might expect, this disease is more common during periods of wet weather. It can cause poor photosynthesis and a reduction in plant yields. Over time, it can reduce the longevity of your plants.
To prevent blight, water in the morning so that the foliage has time to dry off. Make sure plants are spaced in rows 6-feet apart so that air can move among the plants to dry them off. You may have to get rid of infected plants, but some fungicides can be effective at getting rid of this disease, too.
5. Dead Stem
Dead stem is a fungal plant pathogen that is closely related to the pathogens responsible for common root rot, stalk rot, ear blight, and other diseases that can affect asparagus and other plants like cereal grains.
Another soil-borne fungus, this disease can spread through infected seeds. Using sterilized equipment, seeds, and growing supplies is essential. There are several resistant cultivars to the dead stem that you can grow and again, making sure the soil is healthy and clear of disease before planting is also essential.
6. Phytophthora Crown, Root, and Spear Rot
This disease is also fungal, caused by the pathogen Phytophthora asparagi. It is most common when soils are wet and starts as soft, water-soaked lesions that begin on the plant just above the soil line. Plants that are infected often become yellow, and you may find that the crowns die off, too.
Crown, root, and spear rot, left untreated, can dramatically shorten the lifespan of your plants.
This disease is best prevented by avoiding planting in wet areas. You can also apply fungicides to get rid of it should it set in.
7. Watery Soft Rot
The good news is that this disease of asparagus is relatively uncommon. It results in watery-looking lesions on your plants that eventually enlarge to look like white mold. Advanced stages of the disease may cause hard black growths.
This disease is often confused with Fusarium rot – it’s only when the mold develops that you can truly tell the difference. It is often spread from plant to plant and is more likely to affect plants that have been wounded somehow. Avoid over harvesting your plants and use sterile tools when you do so. Again, maintaining proper watering and soil conditions is ideal.
8. Asparagus Mosaic Virus
There are few viral diseases to which asparagus is prone, but asparagus mosaic virus is one of them. This disease often goes unnoticed with very few visible symptoms. However, it can dramatically decrease your yields and make your plants more likely to suffer from other diseases.
Occasionally the virus will also cause a “mosaic” pattern of light and dark green mottling on the plant.
Removing infected plants can help, as can moving plants to new spots if the virus has been detected in the original planting location. The virus can sometimes be seed-borne, so make sure you are using certified seed stock to start your plants. Pests like aphids can also spread it, so you will have to control insects in your garden as well.
This virus can overwinter on your plants so clean up the garden after each growing season and keep weeds under control.
9. Zopfia Root Rot
Zopfia root rot is an asparagus-specific disease that can lead to root rot when plants are wounded or weakened. It spreads slowly in the rhizome at first, but then moves quickly in the roots, forming dark cankers.
Again, this disease can be tough to treat and prevent, but following good watering and ventilation practices can help keep it at bay.
10. Gray Mold Shoot Blight
Gray mold shoot blight, often known simply as gray mold, is caused by a fungus named Botrytis cinerea. It affects many kinds of plants in addition to asparagus, such as strawberries and wine grapes.
The most obvious sign of an infestation is the development of gray masses and rot. It is most common in wet, humid conditions and in soils with a low pH. Standing water harbors spores and makes it possible for the disease to live a long time in the soil.
Avoid placing your asparagus plants too close together and water first thing in the morning so the plants have time to dry out at night. Ventilation and airflow are crucial in preventing this disease. You should also avoid over fertilizing with excess nitrogen, as it can increase the incidence of disease.
Finally, be sure to harvest asparagus every year (after the first year, of course). There’s evidence that regularly pruning and purposely removing bits of plants can help keep this disease at bay. There are some fungicides you can use, too, but many strains of this fungus are resistant, so you’ll have to use them sparingly.
Fusarium crown and root rot of asparagus occurs wherever asparagus is grown. The pathogens Fusarium oxysporum f. sp. asparagi, Fusarium proliferatum, F. redolens, and Fusarium solani are ubitquitous in soil and on seeds. The review is structured to focus on management strategies that affect the three components of the disease triangle: pathogen, host, and environment. An analysis of each strategy is discussed in regard to knowledge gaps and future direction.
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Greenhouse Plants, Ornamental-Fusarium Damping-off, Wilt, and Root Rot
Cause Several Fusarium spp. are possible with Fusarium oxysporum the most prevalent, however, F. commune is common and damaging in conifer container seedlings. Many different plants are susceptible from woody perennials to herbaceous annuals. Damping-off (pre or post emergence) due to Fusarium has been a problem in the PNW on delphinium, Douglas-fir, petunia, and pine as well as vegetables, all grown in the greenhouse. Wilt and root rots have been a problem on these same plants and also carnation, cyclamen, marigold, and Zinnia. Basal rots of bulbs or corms grown in containers have been a problem for gladiolus, iris, and tulip.
These are soilborne fungi that infect plant roots or wounded cuttings. They survive in the soil as thick-walled, dormant chlamydospores, and on wooden benches used for plant production in the greenhouse. Chlamydospores germinate in response to exudates from nearby plant roots. Hyphae then penetrate the roots (wounded or not), colonize the cortex, and move into the xylem tissue which becomes brown. Small spores (microconidia) are produced and carried up into the plant. Infection of the vascular system interferes with water and nutrient absorption. As the plant dies, the fungus erupts through the epidermis and forms tuft-like structures called sporodochia. Spores formed on these tufts can become airborne and infect nearby soils and plants. These macrospores and mycelium in the host tissue convert to chlamydospores and are released into the environment as the tissue decomposes.
The fungus can be spread by soil, wind, water, infected cuttings and contaminated tools, equipment, and clothing. Growing media often gets contaminated by field soil when it is introduced via seeds, tools or even surface sources of irrigation water. Poorly cleaned containers from a previous crop may also contain enough of the fungus to affect the next crop. Fungus gnats may also spread propagules of Fusarium .
Warm temperatures and conditions favor these diseases. Fusarium are stimulated by high temperatures, near neutral pH conditions, and by nitrogen (especially ammonia) fertilization, particularly early in the growth cycle. Potting media with peat or coir fiber are also conducive to disease development.
Most Fusarium spp. can colonize seedling root systems without eliciting disease symptoms. Severe root disease symptoms often become evident when seedlings are stressed. This is especially true for woody perennials stressed to initiate bud formation and begin hardening. Stresses from media being too wet or fertilizer burn can induce disease development. Symptoms typical of Fusarium, however, can be due to other pathogens including Rhizoctonia, Pythium and Phytophthora. It is not easy to tell these organisms apart by visual inspection so send to a Plant Clinic for diagnosis.
Amendment of soil with compost or manure with high levels of organic nitrogen has reduced incidence of the disease in carnation production. Suppression of fungus gnats has been reported to prevent spread.
Symptoms Poor stand development or seedling collapse are indicative of damping-off. Seeds or emerging radicles may be rotted. After emergence, stem, root, and cotyledon may rot at or below the soil line. In petunia, darker-red lesions that become brown with reddish borders develop, or brown lesions with diffuse margins, or similarly discolored longitudinal streaks. It is difficult to determine which organism(s) is involved by causal observation so send into a Plant Clinic for an accurate diagnosis.
Wilt - Lower leaves of carnation yellow, wilt, and dry up one side of the plant. Symptoms progress up the plant. The stem often shrivels and turns grayish and the xylem tissues turn brown. Shoots may be stunted and grow abnormally. The top of the main shoot grows at a right angle to the main stem. Plants may curl when symptoms develop on one side of the plant. Cyclamen corms in cross-section shows patches of reddish-brown-to-black, or purple, discoloration in the vascular system. Roots exhibit vascular discoloration and may be totally discolored and darkened.
Root rots - Late in disease development carnation roots and stems rot and the plant dies. In marigold, root production is greatly reduced, and a dark-colored root rot may be observed. In wet weather, salmon-color spore masses may form on infected stems.
Basal rots - When diseased tulip bulbs are forced in the greenhouse for flowering, stunted growth and leaf yellowing occurs within a few weeks. Plants generally die before flowering. The basal plate and roots decay and become a dull gray. The decay spreads to the bulb scales and lower stem.
Cultural control Clean growing surfaces, clean water, sanitation and handling practices along with soilless media are all essential. Integration of several tactics is needed to manage this disease.
- Use culture-indexed plants free of the pathogen. Purchase new, clean seed.
- Use soilless potting mix or steam-treated soil and rooting media. Steam 30 min. at 180°F. Keep field soil out of contact with clean media.
- Avoid reusing pots or trays from a previous crop for propagation. If pots or trays must be reused then wash off all debris and soak in a sanitizing solution or treat with aerated steam for 30 min. Also disinfect any tools and equipment that might be used and contaminate the media.
- Maintain adequate fertility for moderate plant growth.
- Monitor soluble salt concentrations regularly. Use media pH and soil wetness appropriate for good crop growth.
- Water such that plants are not wet for extended periods of time.
- Remove plant debris during production and thoroughly clean and sterilize the greenhouse between production cycles.
- Control fungus gnats especially during rooting.
Chemical control All materials have shown inconsistent efficacy from trial to trial. Not effective as a sole treatment but must be integrated with cultural controls. Chemical treatment should be preceded by an accurate diagnosis since most of the chemicals are not effective against all possible pathogens. Use these materials preventively only at seeding or transplanting. Do not use to salvage the crop, as treatments are generally ineffective and only help increase the risk of developing resistant fungi. Rotate among fungicides from different groups with different modes of action. Be sure to check labels for crop safety before application.
- Heritage at 1 to 8 oz/100 gal water plus a non-silicone-based wetter sticker. Group 11 fungicide. 4-hr reentry.
- Medallion WDG at 1 to 2 oz/100 gal water. Use with oils or adjuvants may damage plants. Group 12 fungicide. 12-hr reentry.
- Terraguard SC at 4 to 8 fl oz/100 gal water. Group 3 fungicide. 12-hr reentry.
- Thiophanate-methyl-based products. Group 1 fungicides. 12-hr reentry.
- Cleary's 3336 EG at 8 to 16 oz/100 gal water.
- OHP 6672 4.5 F at 7.5 to 20 fl oz/100 gal water.
- Trinity at 8 to 12 fl oz/100 gal water is registered for crown and basal rots. Group 3 fungicide. 12-hr reentry.
Biological control Use in conjunction with other control tactics such as thorough sanitation. Although registered, data on their efficacy in the PNW may be lacking.
- Asperello T34 ( Trichoderma asperellum strain T34) at 0.35 oz/35 sq ft of substrate before potting. See label for details. 12-hr reentry. O
- Bio-Tam 2.0, Tenet WP, or Obtego ( Trichoderma asperellum and T. gamsii ) at 0.5 to 1.5 lb/cubic yard of substrate. See label for details. No restrictions on reentry when soil incorporated. O
- LALStop G46 WG ( Gliocladium catenulatum strain J1446) at 0.33 oz/5 gal water. Do not use with other products in the tank. 4-hr reentry. O
- LALStop K61 WP ( Streptomyces Strain K61) at 0.07 oz/100 to 200 sq ft. Apply with enough water to move product into the root zone. Can be used as a soil spray, drench, dip or incorporated into potting media. 4-hr reentry. O
- Mycostop ( Streptomyces Strain K61) at 1 to 2 grams/100 sq ft. Apply with enough water to move product into the root zone. Can be used as a soil spray, drench, dip or incorporated into potting media. 4-hr reentry. O
- Prestop ( Gliocladium catenulatum strain J1446) at 0.33 oz/5 gal water. Do not use with other products in the tank. 4-hr reentry. O
- RootShield Plus Granules ( Trichoderma harzianum Rifai strain T-22 and T. virens strain G-41) at 1 to 3 lb/cubic yard soil mix. Some California nurseries report it helps, but efficacy in the Pacific Northwest is unknown. IR-4 reports poor to mediocre efficacy. Zero-hr reentry. O
- SoilGard 12 ( Gliocladium virens strain GL-21) at 2 to 4 oz/100 gal water. Unknown efficacy in the PNW. Group BM02 fungicide. 4-hr reentry. O
- Subtilex NG ( Bacillus subtilis stain MBI 600) at 0.2 to 0.4 oz/100 gal is registered as a drench. Unknown efficacy in the PNW. Group BM02 fungicide. 4-hr reentry. O
- Triathlon BA ( Bacillus amyloliquefaciens strain D747) at 0.5 to 6 quarts/100 gal water. Group BM02 fungicide. 4-hr reentry. O
Reference Dumroese, R. K., and James, R. L. 2005. Root diseases in bareroot and container nurseries of the Pacific Northwest: epidemiology, management, and effects on outplanting performance. New Forests 30:185-202.
Borrero, C., Trillas, I., and Avilés, M. 2009. Carnation fusarium wilt suppression in four composts. European Journal of Plant Pathology 123:425-433.
Cultural Methods May Help Your Crop Survive
Since the pathogens that attack the crowns and roots of asparagus plants are ubiquitous in the soil, you cannot easily avoid them.
However, by carefully tending your plants to prevent undue stress, you may be able to produce a good crop in spite of the presence of these fungi and water molds.
Have you battled crown and root rot in your asparagus patch? If so, let us know in the comments!
And for more information about growing asparagus in your garden, have a look at these guides next:
© Ask the Experts, LLC. ALL RIGHTS RESERVED. See our TOS for more details. Product photo via ITS. Uncredited photos: Shutterstock. With additional writing and editing by Allison Sidhu.
About Helga George, PhD
One of Helga George’s greatest childhood joys was reading about rare and greenhouse plants that would not grow in Delaware. Now that she lives near Santa Barbara, California, she is delighted that many of these grow right outside! Fascinated by the childhood discovery that plants make chemicals to defend themselves, Helga embarked on further academic study and obtained two degrees, studying plant diseases as a plant pathology major. She holds a BS in agriculture from Cornell University, and an MS from the University of Massachusetts Amherst. Helga then returned to Cornell to obtain a PhD, studying one of the model systems of plant defense. She transitioned to full-time writing in 2009.