Influence of Nemaguard and Lovell rootstocks and Macroposthonia xenoplax on bacterial canker of peach.

'Fay Elberta' peach trees grown on either 'Lovell' or 'Nemaguard' rootstocks in sandy soil in a lathhouse were highly susceptible to bacterial canker if inoculated with the nematode Macroposthonia xenoplax and the bacterium Pseudomonas syringae. If either one of these organisms were omitted, serious bacterial canker did not develop. Cankers appeared later and remained small when nematodes were omined. Very few cankers appeared on trees not inoculated with the bacterium. Peach trees on both rootstocks were good hosts for, and were stunted by, nematodes. Larger numbers of fruit were produced on trees free of bacterial canker or nematodes. Differences in magnitude of bacterial canker symptoms produced experimentally in different years are considered.