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Adjustment of soil‐surface pH and comparison with conventional fungicide treatments for control of lettuce drop ( Sclerotinia minor )
Author(s) -
Wilson C. R.,
DeLittle J. A.,
Wong J. A. L.,
Schupp P. J.,
Gibson L. J.
Publication year - 2005
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.1365-3059.2005.01188.x
Subject(s) - fungicide , loam , germination , horticulture , biology , soil ph , sclerotinia , agronomy , procymidone , soil water , chemistry , ecology
The use of soil‐surface applications of finely powdered calcium hydroxide (Ca(OH) 2 ) to inhibit Sclerotinia minor sclerotial germination and infection at the collar region of lettuce plants is described. In the laboratory, a pH > 8·0 reduced sclerotial germination of the three S. minor isolates tested. In the glasshouse, surface applications of 2–10 t Ca(OH) 2 ha −1 raised the pH of the top 1–2 cm of a duplex sandy loam soil above 8·5 for at least 8 weeks without affecting soil pH within the transplant root zone. There was a linear relationship between the rate of Ca(OH) 2 applied and disease control, with complete disease suppression at 10 t Ca(OH) 2 ha −1 . In field trials on two soil types (duplex sandy loam, pH 6·0; and red ferrosol, pH 6·9), a rate of 2·5 t Ca(OH) 2 ha −1 , maintained soil‐surface pH above 8·5 for 1–3 weeks and provided up to 58% reduction in lettuce drop. Application of polyvinyl alcohol (a soil‐conditioning polymer) over the Ca(OH) 2 layer appeared to reduce Ca(OH) 2 loss by wind, but did not improve retention of raised soil‐surface pH or disease suppression. Ca(OH) 2 treatment gave similar disease control to the industry standard treatment of a procymidone‐based fungicide seedling drench. A combined treatment of Ca(OH) 2 and fungicide drench gave greater control than either individual treatment, and equivalent control to fungicide drench and three procymidone foliar sprays, offering integrated management options. The use of soil‐surface‐applied Ca(OH) 2 with fungicides, rotation and drip irrigation offers an opportunity for enhanced and sustainable control of lettuce drop.