The potential for the biological control of cavity-spot disease of carrots, caused by Pythium coloratum, by streptomycete and non-streptomycete actinomycetes

Summary. Glasshouse trials were conducted to examine the effect of lime or gypsum amendments on the development of cavity spot disease of carrots in soil artificially infested with Pythium coloratum. Each amendment was applied to soil from the field at 4000 or 8000 kg/ha. Lime at both application rates significantly (P<0.05) reduced the incidence of the disease. In contrast, both gypsum treatments had no effect on the incidence of cavity spot disease. There was no significant (P>0.05) difference in calcium concentration between carrot roots grown in unamended, lime- or gypsum-amended soil with or without the pathogen. Calcium did not appear to play a direct role in the reduction of cavity spot disease. Under the controlled conditions of this glasshouse trial, reduction in the incidence of cavity spot appeared to be related to the increase in soil pH associated with the application of lime. Field trials at the site of soil collection will confirm whether this mechanism is related to field reduction of the disease following liming.

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Microbiological differences between limed and unlimed soils and their relationship with cavity spot disease of carrots (Daucus carota L.) caused by Pythium coloratum in Western Australia

Plant and Soil ◽

10.1007/bf00011443 ◽

1996 ◽

Vol 183 (2) ◽

pp. 279-290 ◽

Cited By ~ 38

Author(s):

Khaled A. El-Tarabily ◽

Giles E. St. J. Hardy ◽

Krishnapillai Sivasithamparam ◽

Ipek D. Kurtb�ke

Keyword(s):

Western Australia ◽

Daucus Carota ◽

Daucus Carota L ◽

Spot Disease ◽

Cavity Spot ◽

Pythium Coloratum

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Association of Pythium coloratum and Pythium sulcatum with cavity spot disease of carrots in Western Australia

Plant Pathology ◽

10.1046/j.1365-3059.1996.d01-8.x ◽

1996 ◽

Vol 45 (4) ◽

pp. 727-735 ◽

Cited By ~ 8

Author(s):

K. A. EL‐TARABILY ◽

G. E. ST. J. HARDY ◽

K. SIVASITHAMPARAM

Keyword(s):

Western Australia ◽

Spot Disease ◽

Cavity Spot ◽

Pythium Coloratum

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Effects of Host Age on Development of Cavity Spot Disease of Carrots Caused by Pythium coloratum in Western Australia Khaled

Australian Journal of Botany ◽

10.1071/bt96045 ◽

1997 ◽

Vol 45 (4) ◽

pp. 727 ◽

Cited By ~ 5

Author(s):

A. El-Tarabily ◽

Giles E. St J. Hardy ◽

Krishnapillai Sivasithamparam

Keyword(s):

Western Australia ◽

Infested Soil ◽

Host Age ◽

Field Soil ◽

Spot Disease ◽

Cavity Spot ◽

Infested Field ◽

Time Of Infection ◽

Pythium Coloratum ◽

Time Of Harvest

Three experiments were conducted with Pythium coloratum Vaartaja, a causal agent of cavity spot disease of carrots in Western Australia, to study the relationships between host age, time of infection and development of cavity spot lesions. Pythium coloratum was isolated frequently from 3-6-week-old asymptomatic roots of carrots grown in soils infested naturally or artificially with the pathogen. Carrots grown in containers of soil artificially infested with P. coloratum, but not those in naturally infested field soil, developed cavity spot lesions after 6 weeks. Early infection of carrot seedlings at or before 3 weeks by P. coloratum in artificially infested soils followed by their transfer to pathogen-free soil was sufficient to cause cavity spot disease at the time of harvest (16 weeks). The disease levels in this treatment were not different from those transferred to P. coloratum-infested soil. There was no significant (P > 0.05) association between carrot age and the ability of P. coloratum to infect the roots and to cause cavity spot lesions at harvest.

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