Monosporascus cannonballus causes a serious disease of melons and watermelons
During the last decades, a group of soilborne diseases of melons and watermelons has become prevalent and causes serious economic losses in various parts of the world. Among responsible fungal pathogens, the ascomycete Monosporascus cannonballus is often reported. Another species Monosporascus eutypoides has also been described but it is now proposed to consider them as synonyms. Symptoms of the disease are characterized by yellowing, death of the leaves, decline of the vines as plants approach maturity. A rapid collapse of the crop is typically observed just before harvest. Affected plants show root lesions, loss of secondary and tertiary roots, and in wet conditions, secondary root rot. Little information is available on the biology and epidemiology of the fungus. Ascospores probably ensure long-term survival of M. cannonballus in the soil. They are released in large numbers into the soil, but as germination is rarely seen, their role in the disease cycle is unknown. The anamorph stage of M. cannonballus is unknown.
Host plants
The main host plants are melons (Cucurbita melo) and watermelons (Citrullus lanatus). In Japan, M. cannonballus has also been reported in the field on Lagenaria siceracia (bottle gourd). Glasshouse experiments have shown that other cucurbits were susceptible (e.g. cucumber, squash, pumpkin). There are reports of the fungus on Achyranthes aspera, Iris, Triticum, Sesamum indicum, Trifolium pratense but pathogenicity has not been demonstrated.
Geographical distribution:
M. cannonballus was first described in 1974 from necrotic melon roots from Arizona (US). It was then reported from Japan, other parts of USA (California, Texas), Israel, Tunisia, Taiwan, Mexico. In Spain, a decline of melons ('colapso', 'muerte subita') has occurred in the Valencia region for the last 10 years but there is disagreement concerning the cause of the disease. It has been attributed to Acremonium sp. by some scientists (see EPPO RS 93/083) or to M. cannonballus by others. The latest reports are from Central America (Honduras, Guatemala), Mexico, Saudi Arabia and from Italy, where the fungus was found in 1997 on watermelons cultivated in the province of Bologna (Emilia-Romagna). This soilborne fungi appears to be adapted to hot, semi-arid climate with soils that tend to be saline and alkaline.
EPPO region: Israel (as M. eutypoides, 1983), Italy (Gennari et al., 1999), Libya (as M. eutypoides, 1978), Spain (Lobo Ruano, 1991), Tunisia (Martyn et al., 1994)
Asia: India, Iran (as M. eutypoides), Japan (Watanabe, 1979), Pakistan (as M. eutypoides), Saudi Arabia (Karlatti et al., 1997), Taiwan (Tsay ; Borkay, 1995)
North America: Mexico (Martyn et al., 1996), USA (Arizona, California, Texas).
Central America: Guatemala (Bruton ; Miller, 1997a), Honduras (Bruton ; Miller, 1997b)
In Texas (US), losses can fluctuate from 10 to 25% from year to year, but in some fields up to 100% loss has been seen. Similar observations are made in southern Spain and Israel. Control of the disease is difficult. So far all tested varieties of melons and watermelons are susceptible. As the fungus shows thermophilic properties, solarization is not expected to provide good results. Soil fumigation can be used against it. The reasons for the sudden appearance and increasing incidence of M. cannonballus on melon and watermelon crops in many parts of the world is not known. Martyn and Miller (1996) suggest that this may be attributed to the availability of reliable detection and identification methods (i.e. molecular tools such as PCR), and particularly to the drastic changes in crop cultivation which took place in the 1980s (e.g. use of plastic mulch, drip irrigation and hybrid cultivars).
Sources
Bruton, B.D.; Miller, M.E. (1997a) Occurrence of vine decline diseases of muskmelon in Guatemala. Plant Disease, 81(6), p 694.
Bruton, B.D.; Miller, M.E. (1997b) Occurrence of vine decline diseases of melons in Honduras. Plant Disease, 81(6), p 696.
CABI (1991) IMI Descriptions of Fungi and Bacteria, nos 1035 ; 1036 (Monosporascus cannonballus ; M. eutypoides]. CABI, Wallingford, UK.
Gennari, S.; Mirotti, A.; Sportelli, M. (1999) [Monosporascus cannonballus on watermelon]. Informatore Fitopatologico, no. 1/2, 38-40.
Karlatti, R.S.; Abdeen, F.M.; Al-Fehaid, M.S. (1997) First report of Monosporascus cannonballus in Saudi Arabia. Plant Disease, 81(10), p 1215.
Lobo Ruano, M. (1991) [Severe diseases of melons and watermelons]. Boletin de Sanidad Vegetal - Plagas, 17(1), 133-163.
Martyn, R.D.; Batten, J.S.; Park, Y.J.; Miller, M.E. (1996) First report of Monosporascus root rot/vine decline of watermelon. Plant Disease, 80(12), p 1430.
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(12), p 1220.
Martyn, R.D.; Miller, M.E. (1996) Monosporascus root rot and vine decline An emerging disease of melons worldwide. Plant Disease, 80(7), 716-725.
Tsay, J.G;; Tung, B.K. (1995) The occurrence of Monosporascus root rot/vine decline of muskmelon in Taiwan. Plant Pathology Bulletin, 4(1), 25-29.
Watanabe, T. (1979) Monosporascus cannonballus, an ascomycete from wilted melon roots described in Japan. Transactions of the Mycological Society of Japan, 20(3), 312-316.
INTERNET
South Texas Vegetable Web (pictures).
http://aggie-horticulture.tamu.edu/southtex/info/watermelon.html
http://aggie-horticulture.tamu.edu/southtex/info/watermelon.html
University of Arizona, Extension Plant Pathology (pictures)
http://ag.arizona.edu/PLP/plpext/diseases/vegetables/melon/melonvd.htm
Texas A ; M University, Department of Plant Pathology and Microbiology (pictures)
http://cygnus.tamu.edu/PLPA/projects/1/monosporascus_cannonballus.html
Data sheet on Monosporascus cannonballus.
http://www.extento.hawaii.edu/kbase/crop/Type/m_cann.htm