Sensitivity of mango anthracnose pathogen, Colletotrichum gloeosporioides, to the fungicide prochloraz in Taiwan.
Kuo KerChung
Author Affiliation: Department of Plant Protection, Bureau of Animal and Plant Inspection and Quarantine, Council of Agriculture, Executive Yuan, Taipei, Taiwan.
Proceedings of the National Science Council, Republic of China. Part B, Life Sciences 25 : 174-179
Abstract : In order to monitor the sensitivity of the mango anthracnose fungus, Colletotrichum gloeosporioides [Glomerella cingulata], to the eradicative imidazole fungicide prochloraz, a total of 43 mango orchards were surveyed throughout the Tainan area in Taiwan, covering a 4000 ha region of mango plantations. These orchards were recognized as having undergone higher prochloraz application. A subpopulation, 55 isolates in total, collected from Wufeng, Taichung, served as a baseline population since no fungicide was ever used in this mango plantation. A total of 545 isolates were surveyed, and it was found that the IC50s (50% inhibitory concentration) fell within a range of 0.009 - 0.1554 µg/ml. No significant resistance was found in the field even with higher frequency of prochloraz application. One orchard (Yujing (Wu)) located in the Yujing area known had a higher frequency of prochloraz application, the IC50s were between 0.0204 - 0.1554 µg/ml. The average IC50 was 0.0766 µg/ml, which was about five times higher than the baseline population (0.015 µg/ml). A significant t test indicated that these two sub-populations were different at p = 0.01. Results indicated that the dose-response of C. gloeosporioides to prochloraz shifted slightly toward higher IC50 over time. A further survey using 10 µg/ml as the threshold dosage was conducted, and the results of 1375 isolates collected throughout this region showed that no isolate could survive at this dosage. Knowing that the registered dosage for field use is 83.3 µg/ml, based on above results, the author concluded that there was no sign of prochloraz resistance in mango plantations 13 years after prochloraz registration in Taiwan.