SADAMCAP, A TECHNIQUE FOR QUANTIFYING POPULATIONS OF PHYTOPHTHORA-CACTORUM IN APPLE ORCHARD SOILS

SADAMCAP (Soil Air-Dried And Moistened Chilled And Plated), proved a s ensitive 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 22 degrees C for 96 h and the n flooded with excess water and chilled at 6 degrees C for 2 h, Plates were sloped and the water was drained, vortexed for 30 s, left at amb ient temperature for 10 min, and then diluted samples were plated on P ARP media and colonies counted after 20, 28, and 40 to 44 h. Detailed studies of each step in the process highlighted the importance of cons istency in experimental procedures. Factors such as the time drained w ater samples were vortexed and how long they remained at ambient tempe rature prior to plating had, respectively, up to a 3.5- and 7-fold eff ect on the colony number. Incubation of soil under lights was essentia l to recover high numbers of P. cactorum colonies.