Monosporascus Cannonball Us - Pathogen Profile Review by Marcel Barbier

Review on a particular Ascomycete that

affects cucurbits

Monosporascus cannonballus

By

Marcel Barbier

University of Florida, Plant Medicine Program Monosporascus cannonballus, Pathogen profile

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INTRODUCTION

Monosporascus cannonballus is considered the main responsible agent of causing the

disease known as sudden wilt, sudden death, root rot and/or vine decline which is a

disease known in arid and semi-arid regions worldwide (4, 7, 16). This fungus has been

reported and investigated worldwide where melon and other cucurbits are commercially

grown in large scale Arizona, California, and Texas in the United States, Guatemala,

Honduras, Japan, Taiwan, Tunisia, Spain, Saudi Arabia, and Israel (3, 11, 14, 17, 19,

21, 24, and 30).

Pivonia, et al., in 2002 reported that fields in the Arava region of southern Israel, melon

(Cucumis melo L.) and watermelon (Citrullus lanatus) crops can be totally destroyed by

the disease in later summer, while disease incidence and severity in crops grown in the

same field during the following winter-spring season mostly are lower (21). Kim et al. in

1995 reported a similar phenomenon observed in Arizona (12). Barbier in 2008 reported

in Guatemala differences between soil temperature and relative humidity in the two

growing seasons (1). Wolff in 1996 also suggested that disease symptoms in melons

are affected by temperature stress in Texas. Pivonia, et al., suggested that soil

temperature differences between the two growing seasons could be an explanation for

these variations in incidence and severity.

Soil disinfestation by fumigation with methyl bromide has been a common and very

effective treatment for soil disinfection including soil pathogens. However, the United

Nations, through the Montreal Protocol, has signatures from over 120 countries banning

methyl bromide by the year 2015. Because methyl bromide depletes the stratospheric

ozone layer, the amount of methyl bromide produced and imported in the United States

was reduced incrementally through the Clean Air Act, and was definitely banned and

phased out in January 1, 2005. Alternatives to replace methyl bromide on controlling

Monosporascus cannonballus have not been as effective as methyl bromide was. In

1996 Martyn et al (16), reported that Metam-sodium, 1,3-dicloropropene, and a mixture

of ethylene dibromide and chloropicrin, were not effective on controlling M.

cannonballus when the products were applied alone without mixing. Since 1996,


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different products (chemical, biological and botanical) and products mixtures application

through the irrigation system, grafting, and solarization technique, has been evaluated,

without obtaining consisting results on controlling Monosporascus spp. in melon,

watermelon and other cucurbit species.

The risk that Monosporascus species continue spreading to other cucurbits cropping

areas is high.

Distribution:

Monosporascus cannonballus has been reported only members of Cucurbitaceae in

arid, hot areas. The most important hosts in the field are melon (Cucumis melo) and

watermelon (Citrullus lanatus) (18). According with the European and Mediterranean

Plant Protection Organization (EPPO), by 2010 Monosporascus cannonballus has been

reported in Europe (Italy, Norway, and Spain); Asia (India, Iran, Iraq, Israel, Japan,

Pakistan, Saudi Arabia, and Taiwan); Africa (Libya and Tunisia); and America

(Guatemala, Honduras, Mexico, United States, and Brazil). EPPO has Monosporascus

cannonballus in the Alert list formerly.

Map of areas in the world reporting Monosporascus spp. (2010)


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Monosporascus genus

During the sixty-second annual meeting of the American Phytopathological Society,

celebrated at Hot Springs, Arkansas, from the 4th to the 8th of October, 1970 Troutman

and Matejka (28) presented the study: Three Fungi associated with cantaloupe roots in

Arizona. They reported that since 1967 they studied the causes of root rots of

cantaloupe and indentified Rhizoctonia solani and Verticillium albo-atrum together with

an unidentified fungus to be responsible of this disease. They reported that the

unidentified fungus did cause the decay of secondary roots that were typified by

numerous scattered, small, round, black bodies (today these bodies are known as

perithecium).

Was not until 1974, when Pollack and Uecker (29) described Monosporascus

cannonballus on secondary roots of Cucumis melo Lineus (cantaloupe) that was grown

in Yuma, Arizona. The report describes the development of the perithecium and the

nuclear cytology of this unusual Ascomycete and compares it with other previously

studied fungi. They found that the development and cytology of Monosporascus

cannonballus is a typical xylarious fungi in most respects, but they also reported that

there are important differences between this fungus and typical xylariaceous fungi. The

ostiole is formed by digestion of the tissues just below the apex of the perithecium,

followed by rupture of the outer wall layers of the apex. Peryphyses are not formed,

and the perithecial wall layers open by a rupture. Every ascus contains nuclei in the

extrasporic cytoplasm as well as in the spore itself, and the number of nuclei initially

included in the spore appears to vary. These characteristics were found to be atypical

to xylariaceous fungi type.

After Monosporascus cannonballus was reported, three other species have been

reported. The first one was Monosporascus eutypoides in 1976. Hawksworth and

Ciccarone (9) indicated that Uecker and Pollack (29) noted a strong resemblance to

Rechingeriella eutypoides Petrak, a species described from decayed roots of some

unidentified plant in Pakistan and authentic material of which they were able to study.

These authors considered that the two were distinct because of the larger ostiolar beaks


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and apparently bitunicate asci in R. eutypoides; Uecker and Pollack agreed with

Hawksworth and Booth (8) that R. eutypoides was not correctly placed in Rechingeriella

Petrak, a genus united with Zopfia Rabenh; by Hawksworth and Booth (8). But was von

Arx in 1976 who considered that R. eutypoides and Bitrimonospora indica belong to

Monosporascus and transferred both to this genus, and since then are synonyms of

Monosporascus eutypoides. Some years later, in 1978 Hawksworth and Booth (8)

conclude that no similar taxon is known apart from Anixiella monospora Malloch & Cain

and was certainly incorrectly placed in the genus Anixiella Saito & Minoura ex Cain, and

consider appropriate to transfer A. monospora to Monosporascus as Monosporascus

monosporus (Malloch & Cain); M. monosporus is only known from Iris rhizomes

originating from Iran. Last Monosporascus specie was reported in 2002 as

Monosporascus ibericus by Collado, González, Stchigel, Guarro and Peláez. They

reported that this fungus is a pyrenomycete that was isolated as an endophyte from

roots and stems of three plant species growing on sand flats and salt marshes in the

Ebro Delta in Spain (6). The main characteristic of this fungus is the presence of a

higher number of ascospores per ascus (up to six), compared to the other species of

the genus: M. cannonballus, M. eutypoides, and M. monosporus; M. ibericus produces

a cleistothecial ascomata with a tomentose peridium and lacks an anamorph. In addition

to the morphological data, the comparative analysis of the ITS-region sequences of

Monosporascus ibericus and the other Monosporascus spp., has supported the

recognition of the new species. A phylogenetic study based on the sequences of the

18S rDNA did not allow us to assess clearly the taxonomic position of the genus

Monosporascus, although the results indicated the genus might have affinities to the

Xylariales rather than to the Sordariales.

Monosporascus species reported up to date:

Monosporascus cannonballus Pollack & Uecker 1974

Monosporascus eutypoides (Petr.) v. Arx 1976

Monosporascus monosporus (Malloch & Cain) D. Hawkswrth & Ciccarone. 1979

Monosporascus ibericus Collado, González, Stchigel, Guarro & Peláez 2002

http://zipcodezoo.com/Fungi/M/Monosporascus_eutypoides.asp

http://zipcodezoo.com/Fungi/M/Monosporascus_monosporus.asp

http://zipcodezoo.com/Fungi/M/Monosporascus_ibericus.asp


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Names:

Monosporascus cannonballus Pollack et Uecker

Classification:

Kingdom: Fungi; Phylum: Ascomycota; Class: Ascomycetes; Order: Sordariales; Genus:

Monosporascus; Species: Monosporascus cannonballus

Morphology:

Produces sexual spores

called ascospores

The ascospores are

produced within an ascus.

The ascus has a layer of

differentiated hyphae

around it, the perithecium

wall.

The perithecium is visible to

the naked eye as small

black bulges in the root

cortex.

Perithecium is imbedded in

or emergent on host roots.

Small necrotic roots 1-3 mm

in diameter often support

large numbers of

perithecium.


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Dimensions: Perithecium has a diameter between 222-568 µm; the base of the

perithecium is wide basally and measures between 74-148 µm, with a neck height that

could measure up to 148 µm. The ascus is between 50-110 by 35-50 µm. The

paraphysis is between 90-200 by 5-12.5 µm. The ascospores are between 32-47.5 µm

in diameter (31).

Main remarks between Monosporascus cannonballus and other species

Monosporascus species are: Monosporascus eutypoides as well as M. cannonballus

produced a perithecium, but M. eutypoides produced two ascospores per ascus instead

of one as happens in M. cannonballus. Monosporascus monospores and

Monosporascus ibericus produce a cleistothecium and not a perithecium, the ascospore

surface in M. monosporus has small pores on the ascospore surface.

Physiological symptoms

Aboveground

Field symptoms first reveal themselves

as underdeveloped plants.

The symptom may go disregarded if the

entire field is uniformly affected.


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Older crown leaves begin to turn chlorotic and then dry and necrotic within weeks

previous to harvest. The decaying of leaves advances very rapid to the end of the

vines, and end by causing the collapse of the vine. Dead of the canopy comes within 1

to 2 weeks after appearance of first foliar symptoms.

The bottom row in this

picture shows a group of

plants that received a

treatment with a botanical

fungicide that diminish

the ascospores

population. The front row

shows the control that did

not receive anything and

shows described

symptoms of

Monosporascus

cannonballus (1)

Fruit of diseased plants are smaller, may abscise from the pedicle before ripening and

have reduced sugar content. Fruit may also become sunburned due to lack of foliage

Number of fruits and size of it is directly correlated with fungus incidence and severity

(1).

Low Medium/Low Medium High


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Stem lesions are generally lacking and above ground symptoms may be confused with

other vine declines caused by Macrophomina phaseolina (charcoal rot), Didymella

bryoniae (gummy stem blight), Lasiodiplodia theobromae (Lasiodiplodia decline), and

Myrothecium roridum (Myrothecium canker) (16, 19).

Belowground Symptoms

Root lesions, root rot, loss of feeder roots and, in severely dry conditions, death of

taproot are results of Monosporascus root rot and vine decline.

Melon roots infected with Monosporascus

cannonballus showing lesions and loss of feeder

roots. Lesions are tan to red-brown. In severe cases

of Monosporascus cannonballus infection, most of

the root system may become necrotic and result in

death of the plant.

Lesions first develop as small areas of necrosis at

the joints between secondary and tertiary roots or at

the tips of young roots. Typically are dry, but with

excess of soil moisture they may appear as a wet

rot. Large, black perithecium form on dead roots and

are visible to the naked eye. The perithecium first

appear on smaller feeder roots in the first few

centimeters of soil and typically appear late in the

season.

Ruptured perithecium releasing ascospores. Shiny,

black, round ascospores are readily released from

the perithecium and are visible with a hand lens (16,

19).


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Disease Cycle and Epidemiology

Monosporascus cannonballus life cycle (1)

Infection of the roots occurs via germinating ascospores or active mycelium in the soil

(A). Barbier (1), suggest that initial infection can occur early in the season, from first

day after transplanting (cotyledons are completely unfolded and first soft not woody

roots are actively growing) up to the time inflorescence emergence (First flower initial

with elongated ovary visible on main stem). Tissue colonization (B, C) starts

immediately and when soil temperature rises is more aggressive. Tissue colonization

occurs during the flowering and production season. Perithecium formation in the roots

(D) occurs between flowering and fruit formation. The perithecium reaches it mature

stage when fruits are completely formed and start filling. The perithecium is ready to

release ascospores (E), when plant collapse happens. Ascospores are released (F, A)

after plant has collapsed and roots are dry.


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Ascospores are thought to be the primary inoculum, however their germination is rare

and the role in infection is unknown. Ascospores are believed to be the long-term

survival structures of the fungus. It is assumed that Monosporascus root rot and vine

decline is a monocyclic disease since no known asexual (anamorph) stage has been

identified (13, 16, 19).

Stanghellini et al (27) reported that ascospores of the fungus were recovered from soil

samples collected from native desert sites, and perithecia of the fungus was observed

on roots of a native plant, Lepidium lasiocarpum, growing in a native habitat.

Stanghellini concludes that Monosporascus sp. is an indigenous soilborne fungus.

Martyn (18) reports that Monosporascus cannonballus is homothallic (self-fertile) and

readily forms fertile perithecium in host root tissue and in vitro on artificial growth media.

Ascospores are thick, multi-walled spores and are extremely resistant to desiccation

and other factors. Germination of the ascospore is rare in vitro, however germination is

enhanced in situ when in the presence of root exudates from growing plants seedlings.

Soil microflora, most likely actinomycetes also are important in the germination of

ascospores in the field. Monosporascus cannonballus is adapted to hot, dry climates.

In vitro vegetative growth is optimal at 25 to 35°C (77 to 95°F), while perithecium are

formed most readily at 25 to 30°C (77 to 86°F). Monosporascus cannonballus may

survive for several days at temperatures up to 55 C°, but is killed within 90 min at 60°C.

Mycelial growth occurs over a pH range of 5 to 9, but is optimal from pH 6 to 7 and

inhibited completely at pH 4 and below. Monosporascus cannonballus appears also to

be adapted to slightly or moderately alkaline and saline soils. The fungus grows readily

on several standard laboratory growth media (e.g. potato dextrose agar, V-8 juice agar,

and water agar) and forms fertile black perithecium within 2 to 3 weeks. Perithecium are

readily visible against the light gray or dirty white mycelium.

Dissemination of Monosporascus cannonballus is unknown. It is likely that it is spread

by movement of infested soil or infected plant material. Ascospores may also be moved

via furrow water or heavy rains. Airborne spread is unlikely due to the large


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ascospores. Vegetative mycelium is effective at inhabiting decaying tissue; however

mycelium will not survive even moderate desiccation (13, 16, 19.)

Management

Management of Monosporascus cannonballus has proven to be difficult do to its heat

tolerance, thick-walled resting structures (ascospores), growing list of host plants and

the lack of genetic resistance in melons and common cultural practices that favor the

pathogen and disease development such as drip irrigation and black plastic mulch (15).

Combined practices that could help managing Monosporascus cannonballus:

Soil treatment with pesticides: Biocides, Chemical fungicides, and/or Biological

fungicides.

Cultural practices: Soil solarization, Grafting, Irrigation, and/or Fruit removal

Soil treatment with pesticides

Use of biocides in the soil: Soil disinfestation by fumigation with methyl bromide was a

common very effective treatment. Because methyl bromide depletes the stratospheric

ozone layer, was definitely banned and phased out in January 1, 2005. Metam-sodium,

1,3-dicloropropene, and a mixture of ethylene dibromide and chloropicrin, are been

used, but these biocides are not as effective as Methyl bromide was on controlling

Monosporascus cannonballus. Stanghellini et al, in 2003 reported that methyl iodide

injected as a hot gas is as effective as methyl bromide on controlling Monosporascus

cannonballus when using the same dose in Kg./Ha (26).

Chemical fungicides: Use of fungicides should be less expensive than fumigation.

Efficacy of different fungicides has been evaluated in vitro in laboratories, with good

results under those conditions (5, 23). Between 2000 and 2010, some selected

fungicides have been evaluated under field conditions (5, 23). Application timing,

frequency, and doses were evaluated. Cohen et al in 2000 evaluated 29 different

fungicides and out of these ones reported that fluazinam and kresoxim-methyl were the


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most effective. Pivonia et al in 2006 (22) reported that the strobilurines: azoxystrobyn,

pyraclostrobin, azoxystrobin + chlorothalonil and the imidazole prochloraz are effective

on controlling Monosporascus cannonballus. The issue regarding the use of these

products is regarding registration and cost. Fludioxonil applied at high rates is also

effective but is phytotoxic. Fluazinam, is less effective than others actually being

evaluated.

Biological fungicides: Sanz et al (25) reported that strains combination of Trichoderma

pseudokoniingii, Trichoderma viride and Trichoderma harzianum are effective on

controlling Monosporascus cannonballus in vitro. Barbier, evaluated a botanical

fungicide based on Melaleuca alternifolia and reported to be effective in controlling

Monosporascus cannonballus in vitro. Under field conditions Barbier evaluated

application timing, frequency, and doses indicating that the botanical fungicide is

effective when four applications were done during the first three weeks in the growing

stage of melon.

Cultural practices

Soil solarization

Melon collapse caused by the heat-tolerant soil-borne fungus Monosporascus

cannonballus is not controlled by current solarization technology applied to large soil

volumes because the temperatures achieved are not high enough to kill the pathogen's

ascospores (5).

Fruit removal

According to Hoon Lee study done in 2003, Monosporascus cannonballus severity on

cantaloupe roots were fruits are removed is less severe than on roots of plants were

fruits are not removed. Fruit removal results in increase root growth and carbohydrate

accumulation in the cantaloupe roots (10). Therefore, the practice of removing fruits

could be used as a cultural practice to retard the development of Monosporascus

cannonballus because a greater carbohydrate accumulation in the cantaloupe root will

occur and the symptoms will not occur as aggressive in plants without fruit removal.


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Pivonia et al (20) in 2001, confirm that plant collapse and death usually occurred during

the fruit maturation period. They reported that fruit removal from infected plants

prevented wilting, but did not prevent tylose formation and the associated increase in

the root resistance to water flow. Infected plants, showing reversible wilt symptoms

and from which fruits were removed, regained leaf turgor and remained alive. The

presence of fruits in Monosporascus cannonballus -infected plants apparently subjects

the plants to progressive water stress till they die. Fruit removal reduced leaf stomatal

conductance and increased root growth, thus enabling the plants to survive the

constraint to water uptake and translocation imposed by the pathogen, through root

destruction, tylose formation and root function.

Breeding and Grafting

Beltran et al (2), in 2008 suggest that disease control by grafting onto genus Cucurbita

seems to be related primarily by the increased resistance of its root system to infection

by M. cannonballus, and recommends the use of grafting as a disease management

measure for the disease.

Importance of Monosporascus cannonballus in the melon industry

According to Martyn (18) Monosporascus cannonballus the responsible agent causing

Sudden death, Root rot and/or Vine decline is an emerging disease worldwide, and was

not having enough attention among plant pathologists around the world.

Monosporascus cannonballus was described as a genus and as new specie by Pollack

and Uecker in 1974, but no pathogenicity trials were conducted at that time (29). The

first confirmed report of pathogenicity was from Israel in 1983 (24). Pathogenicity of

isolates from the United States was first reported in 1991 by Mertely et al. in Texas, and

the disease was named Monosporascus root rot and vine decline (19). Up to date

Monosporascus cannonballus has been reported in 18 countries, and it is very probable

that it will be reported in additional countries in the near future.


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Bibliography:

1. Barbier, M. (2008) Evaluation of BM-608 (Melaleuca alternifolia) oil extract on controlling sudden wilt (Monosporascus cannonballus) in melon (Cucumis melo). Zacapa, Guatemala. Unpublished research done for Biomor Israel Ltd.

2. Beltran R.; Vicent, A.; Garcia-Jimenez J. and Armengol, J. (2008). Comparative epidemiology of Monosporascus root rot and Vine decline in Muskmelon, Watermelon, and Grafted Watermelon crops.

3. Bruton, B. D. & Miller, M. E. (1997). Occurrence of vine decline disease on muskmelon in Guatemala. Plant Disease, 81, 694.

4. Cohen, R., Pivonia, S., Shtienberg, D., Edelstein, M., Raz, D. & Garstl, Z. (1999). The efficacy of fluazinam in suppression of Monosporascus cannonballus, the causal agent of vine decline of melons. Plant Disease, 83, 1137-1141.

5. Cohen, R.; Pivonia, S.; Burger, Y.; Edelstein, M.; Gamliel, A.; and Katan J. (2000). Toward integrated management of Monosporascus wilt of melons in Israel.

6. Collado, J., González, A., Platas, G., Stechiguel, A. M., Guarro, J. & Pelaez, F. (2002). Monosporascus ibericus sp. nov., an entophytic ascomycete from plants on saline soils, with observations on the position of the genus based on sequence analysis of the 18 S rDNA. Mycological Research, 106, 118-127.

7. European and Mediterranean Plant Protection Organization (EPPO) 21 boulevard Richard Lenoir, 75011 Paris, FRANCE

8. Hawksworth D. L. and Booth C. (1974) A Revision of the genus Zopfia Rabenh. Mycol. Papers 135: 1-38.

9. Hawksworth D. L. and Ciccarone A. (Commonwealth Mycology Institure, Ferry Lane, Kew, Surrey TW9, England; and Instituto di Patologia Vegetale, Universita degli studi di Bari, via Giovanni Amendola 165/A, 70126 Bari, Italy) 1978. Mycopathologia vol. 66,3: 147-151.

10. Hoon Lee, J. 2003. Effect of fruit removal on carbohydrate concentrations of Cantaloupe (Cucumis melo L.) roots in naturally infested soil with Monosporascus cannonballus.

11. Karlatti, R. S., Abdeen, F. M. & Al-Fehaid, M. S. (1997). First report of Monosporascus cannonballus on melons in Saudi Arabia. Plant Disease, 81, 1215.

12. Kim, D. H., Rasmussen, S. L., & Stanghellini, M. E. (1995). Monosporascus cannonballus root rot of muskemelon: root infection and symptoms development in relation to soil temperature. Phytopathology, 85, 1195 (Abstr.).

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16. Martyn, R. D., & Miller, M. E. (1996). Monosporascus root rot and vine decline, an emerging disease of melons worldwide. Plant Disease, 80, 716-725.

17. Martyn, R. D., Lovic, B. R., Maddox, D.A., Germash, A., & Miller, M. E. (1994). First report of Monosporascus root rot/vine decline of watermelon in Tunisia. Plant Disease, 78, 1220.

18. Martyn, R.D. 2002. Monosporascus root rot and vine decline of melons. The Plant Health Instructor. DOI: 10.1094/PHI-I-2002-0612-01. Updated 2009.

19. Mertely, J. C., Martyn, R. D., Miller, M. E. & Bruton, B. D. (1993). An expaned host range for the muskmelon pathogen Monosporascus cannonballus. Plant disease, 77, 667-673.

20. Pivonia, S., Chen, R. Katan, J. And Kigel J. 2001. Effect of fruit load on the water balance of melon plants infected with Monosporascus cannonballus.

21. Pivonia, S., Cohen, R.,Kigel, J. & Katan, J. (2002). The effect of soil temperature on disease development in melon plants infected by Monosporascus cannonballus. Plant Pathology, 51, 472-479.

22. Pivonia, S.; Gerstl, Z.; Maduel, A.; Levita, R. and Cohen R. (2010) Management of Monosporascus sudden wilt of melon by soil application of fungicides.

23. Pivonia, S; Levite, R; Maduel, A. And Cohen, R. 2009. Chemical control of the sudden wilt disease in melons caused by Monosporascus cannonballus.

24. Reuveni, R., & Krikun, J. (1983). The occurance and distribution of Monosporascus eutypoides under arid zone conditions in Israel. Transactions of the British Mycological Society, 80, 354-356.

25. Sanz, L., Sales, R., Armengol, J., Monte, E., Garcia-Jiménez, J. y Grondona, I. Antagonismo de Trichoderma spp. frente a Monosporascus sp. Y Acremonium cucurbitacearum causantes de colapso en melón.

26. Stanghellini, M.; Ferrin, D.; Kim, D.; Waugh, M.; Radewald, K.; Sims, J. and Ohr H. (2003) Application of preplant fumigants via drip irrigation systems for the management of root rot of melons caused by Monosporascus cannonballus.

27. Stanghellini, M.; Kim, D.; and Rasmussen S. (1996) Ascospores of Monosporascus cannonballus: Germination and distribution in cultivated and desert soils in Arizona.

28. Troutman, J. and Matejka J. (1970). Three Fungi associated with cantaloupe roots in Arizona. Phytopathology. 60 Annual Meeting Abstracts: 1,317.

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30. Watanabe, T. (1979). Monosporascus cannonballus, an ascomycete from wilted melon roots undescribed in Japan. Transactions of the Mycological Society of Japan, 20, 312-316.

31. Watanabe, T. (2002). Pictorial atlas of soil and seed fungi. Morphologies of cultured fungi and key to species. Second edition.

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Monosporascus Cannonball Us - Pathogen Profile Review by Marcel Barbier