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Control of Phytophthora root rot of irrigated subterranean clover with potassium phosphonate in Victoria, Australia
Author(s) -
GREENHALGH F. C.,
BOER R. F.,
MERRIMAN P. R.,
HEPWORTH G.,
KEANE P. J.
Publication year - 1994
Publication title -
plant pathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.928
H-Index - 85
eISSN - 1365-3059
pISSN - 0032-0862
DOI - 10.1111/j.1365-3059.1994.tb01650.x
Subject(s) - biology , root rot , agronomy , mycelium , pasture , trifolium subterraneum , potassium , horticulture , phytophthora , chemistry , organic chemistry
Phosphonic acid was more effective in inhibiting the production of sporangia of Phytophthora clandestina in sterile pond water (ED 50 = 1·4 p.p.m.) than it was in inhibiting the growth of mycelium of the fungus on either corn meal agar (ED 50 = 13·8p.p.m.) or lima bean agar (ED 50 = 236 p.p.m.). Experiments under controlled environmental conditions showed that better control of tap root rot of subterranean clover caused by P. clandestina was achieved by application of potassium phosphonate to a pasteurized soil mixture than by a spray on the foliage alone. However, in a soil from a pasture, foliar sprays were more effective than soil treatments. Application of superphosphate at a rate of 250 kg/ha or higher to the soil reduced the effectiveness of sprays. In three experiments in irrigated pastures a spray of potassium phosphonate at 300 or 313 ml/ha, applied to cotyledons of subterranean clover and to soil, reduced severity of Phytophthora root rot and increased the annual production of dry matter of the legume by 1·96 to 5·11 t/ha in comparison with untreated controls.