Chemical and Cultural Control for FHB and Mycotoxin Contamination in Japan

摘要

The provisional standard of 1.1 ppm for deoxynivalenol (DON) in wheat was determined by Japanese government in 2002. Therefore, the objective of our research has to be changed from controlling disease severity to control of mycotoxin contamination. Re-evaluation of registered fungicides and screening new candidates for control of mycotoxin contamination are considered mandatory.rnWe found that seven chemicals; metoconazole, tebuconazole, captan, thiofanate-methyl, oxine-copper, copper-hydroxide and phosphorous acid would control DON and NIV. On the contrary, treatment of azoxystrobin significantly increased the level of DON and NIV compared to the control plots, even though it reduced disease severity of FHB. In conclusion, I propose new fungicide evaluation system based on efficacy for mycotoxin contamination.rnIn Japanese wheat production, non-till or minimum tillage is not practied and the area of a wheat field is relatively small. Therefore, cultural practice to decrease residue is practical option. Soil top dressing is a traditional cultural practice in Japan. The aims of the practice are to recover root activity from the damage by frost heaving and to reduce non-available tillers. We tested a hypothesis that this cultural practice reduces disease incidence in winter wheat. Field experiments were conducted for 4 years in upland conditions in the northern part of Japan; residues and lower leaves infected with pink snow mold or powdery mildew were completely covered with soil at R4 and R9 growth stages. Perithecia of Microdochium nivale on the leaf sheath and lesion on the flag leaf decreased by 100 % and 92 % respectively. The number of diseased spikes by FHB decreased by 76%. However, in the paddy field, top soil dressing was not so effective because of the preseace of a high rice residue which is a primary inoculum source of FHB. We plan to test the combination of this practice with other cultural practices of burning, up-cut rotary and carry out in paddy field.rnChemical ControlrnThe provisional standard of 1.1 ppm for deoxynivalenol (DON) in wheat was determined by the Japanese government in 2002. Therefore, the objective of our research has to be changed from controlling disease severity to control of mycotoxin contamination. Re-evaluation of registered fungicides and screening new candidates for control of mycotoxin contamination are considered mandatory. We tested totally 24 kinds of fungicides with differing modes of action. Three experiments were conducted for two years (Nakajima et. al, 2004). In the paddy field we sprayed fungicides at two days before flowering and 5 days after flowering. Inoculations were done just flowering and 7 days after flowering. In 2002 we used DON producer, in 2003 mixture of DON and NIV producer were sprayed. A sprinkler was used to promote disease development. In addition, experiment in upland fields was done in 2003. Corn grain inoculum of a mixture of DON and NIV producer were used under natural rainfall condition.