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Poster: Biology & Disease Mgmt: Integrated Pest Mgmt


Effect of temperature and sugar beet growth stage on yellowing decline caused by Fusarium secorum
M. KHAN (1) (1) North Dakota State University and University of Minnesota, U.S.A.

Fusarium yellowing decline caused by Fusarium secorum was recently reported in Minnesota. Conditions favorable for disease development were determined using three isolates (12-4P, 12-2P and 1189), three temperatures (55°C, 65°C, and 75°C), and three growth stages (3, 5 and 7 weeks old plants [WOP]). One F. oxysporum f. sp. betae isolate was used for comparison. Plants were inoculated using root dip (105 microconidia or macroconidia ml-1) for two minutes. Evaluation for foliar symptoms was done every two days until harvest 35 days after inoculation, and area under disease progress curve (AUDPC) was calculated. Temperatures of 75 and 65°C were more favorable for disease development than 55°C. The mean AUDPC were 38, 29, and 4 for 12-4P, 12-2P and 1189 isolates, respectively. 12-4P isolate had significantly higher AUDPCs at 75 and 65°C for 3 WOP compared to both 5 and 7 WOP. 12-2P isolate resulted in no significant differences between AUDPCs at 3, 5, and 7 WOP within each temperature. However, 12-2P isolate caused significantly more disease at 75°C and 65°C compared to 55°C for 3 and 5 WOP. Isolate 1189 was least aggressive with no significant differences in AUDPC among all combinations of temperature and growth stage. Isolates 12-4P and 12-2P resulted in higher AUDPC than F. oxysporum f. sp. betae at the same temperature and sugar beet growth stage. Results suggest early planting in cool soils may help to manage the disease.