Survival of Xanthomonas cucurbitae in the field

This study was conducted to assess survival of Xanthomonas cucurbitae, incitant of bacterial spot of cucurbits, in the field. Symptomatic pumpkin leaves and fruits infected with X. cucurbitae were collected from two commercial fields in Illinois. A factorial experiment was performed at the University of Illinois Fruit and Vegetable Research Farm in Urbana, Illinois. Factors investigated in the experiment were: 1) the location of the fields from which the leaves and fruits were collected; 2) the nature of pumpkin tissue; 3) burial depth; and 4) recovery date. The experimental sample was composed of either five leaves or two fruit pieces in fiberglass mesh bag, which were buried at either 0-10 cm or 10-20 cm deep. Viability of X. cucurbitae in the pumpkin tissues was assessed after 6, 9, 12, 15, 18, and 24 months. Viable X. cucurbitae was still recovered from the buried samples after 24 months. The nature of the pumpkin tissue and the burial time had significant (P=0.0001) impact on survival of X. cucurbitae. Conversely, the location of the fields with the affected pumpkin plants (P=0.7932) and the burial depth (P=0.0870) did not significantly affect the number of X. cucurbitae colony forming units recovered from the buried samples.