BACTERIAL SPOT OF PEACH AS INFLUENCED BY WATER CONGESTION, LEAF WETNESS DURATION, AND TEMPERATURE

Development of bacterial spot on Suwanee peach leaves after inoculatio n with Xanthomonas campestris pv. pruni was studied at 24 and 30 degre es C and after-inoculation wetness periods of 0, 6, 18, 24, and 48 h. Water congestion following leaf wetness resulting from exposure to 100 % relative humidity for at least 36 h and growing plants in sandy soil were necessary for symptom development. Symptom development was slowe r at 24 than at 30 degrees C. Postinoculation wetness periods greater than 18 h were necessary for extensive symptom development at 24 but n ot at 30 degrees C. However, some symptom development was evident at e ither temperature with no leaf wetness after inoculation if leaves wer e water-congested. Symptoms did not develop when trees were grown in a sandy loam-vermiculite soil mixture.