VIEW ARTICLE

Techniques

SADAMCAP, a Technique for Quantifying Populations of Phytophthora cactorum in Apple Orchard Soils. I. J. Horner, Horticulture and Food Research Institute of New Zealand, P.O. Box 92-169, Auckland; W. F. Wilcox, Department of Plant Pathology, Cornell University, New York State Agricultural Experiment Station, Geneva 14456. Phytopathology 85:1400-1408. Accepted for publication 1 September 1995. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/Phyto-85-1400.

SADAMCAP (Soil Air-Dried And Moistened Chilled And Plated), proved a sensitive and repeatable technique for assessing Phytophthora cactorum populations in apple orchard soils. Air-dried soil in petri plates was moistened and incubated under lights at 22ºC for 96 h and then flooded with excess water and chilled at 6ºC for 2 h. Plates were sloped and the water was drained, vortexed for 30 s, left at ambient temperature for 10 min, and then diluted samples were plated on PARP media and colonies counted after 20, 28, and 40 to 44 h. Detailed studies of each step in the process highlighted the importance of consistency in experimental procedures. Factors such as the time drained water samples were vortexed and how long they remained at ambient temperature prior to plating had, respectively, up to a 3.5- and 7-fold effect on the colony number. Incubation of soil under lights was essential to recover high numbers of P. cactorum colonies.