Phytopathology (2004) 94, 780-788

E.J. Fichtner, D.M. Benson, H.G. Diab and H.D. Shew (2004)
Abiotic and biological suppression of Phytophthora parasitica in a horticultural medium containing composted swine waste
Phytopathology 94 (7), 780-788
Abstract: Horticultural potting media have been amended with compost to enhance biological suppression and with Al₂(SO₄)₃ to enhance abiotic suppression of plant pathogens, but these factors have not been simultaneously incorporated into the same medium. In this study, the efficacy of aluminum (Al)-amended potting medium containing 20% composted swine waste (CSW) was assessed for control of Phytophthora parasitica (syn. P. nicotianae), a soilborne pathogen causing damping-off of many horticultural bedding plants. Steamed and unsteamed media were amended with no Al or Al at 0.0079 g of Al g^-1 of medium with an Al₂(SO₄)₃ solution at either pH 4 or pH 6. Infested leaf disks were buried for 2-day durations beginning 0, 6, 13, and 21 days after Al amendment. The number of sporangia produced on infested leaf disks was assessed. A similar experiment was conducted to determine the effect of steaming and Al amendments on pathogen populations. Medium treated with the pH 4 solution consistently reduced sporangia production between 38 and 65% on day 0, but no Al effect was noted at subsequent time points. The pH 6 amendment did not consistently affect sporangia production. Exchangeable Al levels decreased over time, and abiotic suppression was only observed at >2 µM Al g^-1 of medium. Pathogen populations were occasionally affected by steaming and Al. Sporangia production in unsteamed medium was reduced by 50% on leaf disks buried on days 6, 13, and 21, but not on day 0. Al amendment of a 20% CSW potting medium enhanced suppression of P. parasitica and abiotic suppression occurred before biological suppression developed.
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Database assignments for author(s): David Shew, D. Michael Benson, Elizabeth J. Fichtner

Research topic(s) for pests/diseases/weeds:
environment - cropping system/rotation

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Phytophthora parasitica		U.S.A. (SE)