Sensitivity of Phytophthora infestans population in Peru to Mefenoxam and Cymoxanil

Transcription

1 Sensitivity of Phytophthora infestans population in Peru to Mefenoxam and Cymoxanil W. Pérez 1, J. Lara 2 and G.A. Forbes 1 1 International Potato Center, Lima, Peru 2 Universidad Nacional Agraria La Molina, Lima, Peru

2 42% of Peruvian potato growing area is endemic for Late blight Losses between US$ 7 to 25 millions/year

3 Climate conducive to LB Subsistence and semi commercial farmers Huánuco (351,239 t/year) First Growing potato area Susceptible potato varieties

4 Farmers spraying fungicides (94.7% ) Number of sprays: 6.6 ( 0-14 ) 1-5 sprays (63%) 6-10 sprays (32%) sprays (5%) Fungicides more used: Metalaxyl Cymoxanil Mefenoxam

5 Lineage: EC-1 PE-3 US-1 PE-7 Lineage EC-1 PERU Mating type: Isoenzyme: GPI PEP Mt DNA: Metalxyl resistance: A1 90/100 96/100 II a Resistant

6 Objectives: To establish a baseline sensitivity for Mefenoxam and cymoxanil To provide a preliminary evaluation of the risk resistance fungicide

7 Materials and methods: Fifty eight isolates collected in All EC -1, mating type A1, all resistant to metalaxyl (Previous results) Metalaxyl resistance test R CONTROL 5 ppm 50 ppm 100 ppm S R MR if growth > 40% of the 0 ppm control at 100 ppm if growth <40% of the control at 100 ppm, but not at 5 ppm S if growth < 40% of the 0 ppm control even at 5 ppm (Therrien et. al. 1993)

8 In Vitro assays: Method emended Agar (V-8 juice) Mefenoxam 95.9% (a.i.) Cymoxanil 98.3 % (a.i.) 10 Concentrations 0.01 to 1000 ppm Stock in DMSO 6 Concentrations 0.01 to 4 ppm Stock in DMSO Incubation at 18 C for 10 days 58 isolates

9 Mean colony diameter (minus diameter of the inoculation plug) Four replications/ isolate/concentration Relative mycelia growth (RMG) Dx = Mean growth diameter on the emended medium RMG = 100 ( Dx 1mm ) ( Dy 1mm ) Dy = Mean growth diameter on non emended agar Daayf and Platt, 2002 EC 50 analyzed by Probit analysis (Statistical Program R)

10 In Vivo assays: Detached leaf Mefenoxam 95.9% (a.i.) 0.01 ppm to 1000 ppm Stock in DMSO Cymoxanil 98.3 % (a.i.) ppm to 4 ppm Stock in DMSO Five isolates with low In vitro EC 50 Concentration 3000 sp/ml Incubation at 18 C for 6 days, photoperiods of 12 hr

11 Detached leaf Area foliar disease Foliar area calculated by Sigma Scan Pro EC 50 analyzed by Probit analysis (Statistical Program R)

12 In Vivo assays: Mefenoxam 95.9% (a.i.) 0.01 to 5000 ppm Sotck in DMSO Whole plants Cymoxanil 98.3 % (a.i.) to 1024 ppm Stock in DMSO Isolate with the lowest EC 50 in Detached leaf assays Concentration 3000 sp/ml, spray run off Incubation at 18 C for 6 days, photoperiods of 12 hr

13 ( arcsenx 1) ) Whole plants Percentage of disease foliar area (7 d.a.i.) Percentages transformed by (arcsen x -1) EC 50 analyzed by Probit analysis (Statistical Program R)

14 Results Sensitivity to Mefenoxam EC50 values (ppm) Mefenoxam Assays Range Mean SD In vitro In vivo Detached leaf Whole plants Data from 58 isolates 2 Data from 5 isolates selected 3 Data from 1 isolate selected

15 Reports worldwide of EC 50 values of Phytopthora infestans isolates to Metalaxyl. Fungicide EC50 Values Range mean Method mg/l 0.2 mg/l Petri dish mg/l 47 mg/l Petri dish Reference Power et. al. (1995) Metalaxyl > 100 ppm a Petri dish Sujkowski et. al (1995) >200 ppm a Whole plants >200 ppm a Detached leaf Sozzi an Staub (1987) 100 ppm a Petri dish ppm Petri dish ppm Whole plant Klinkennberg et. al. (1998) µg/ml b Detached leaf Holmes and Channon (1984) 182 c Petri dish Porter et al (2007) a Values not considered as range. Values reported as sensibility up to or more than this value. b Authors reported treatment with metalaxyl at 1000 or 2000 µg/ml was associated with phytotoxic symptoms. c Value reported for P. erythroseptica Equivalence : 1ppm = 1mg/l, 1µg/g, 1mg/kg

16 Sensitivity to Cymoxanil EC50 values (ppm) Cymoxanil Assays Range Mean SD In vitro In vivo Detached leaf Whole plants Data from 58 isolates 2 Data from 5 isolates selected 3 Data from 1 isolate selected

17 Reports worldwide of EC 50 values of Phytopthora infestans isolates to Cymoxanil. Fungicide EC50 Values Range mean Method Reference mg/l 0.42 mg/l Petri dish 0.22 mg/l b 0.46 mg/l c Petri dish Hamlen and Power (1998) 0.22 mg/l b 0.50 mg/l c Petri dish Cymoxanil < 10 ppm a 0.8 ppm Petri dish 3 mg/l Detached leaf Sujkowski et. al (1995) Gisi et. al (1997) Ziogas and Davidse (1987) 1 µg/ml Petri dish mg/l 0.17 mg/l Petri dish mg/l 0.3 mg/l Petri dish Power et. al. (1995) a Values not considered as range. Values reported as sensibility up to or more than this value. b Values reported pre-commercialization of the fungicide. c Values reported after 10 or more years after commercialization. Equivalence : 1ppm = 1mg/l, 1µg/g, 1mg/kg

18 Commercial fungicide formulations based on metalaxyl (Mefenoxam) and Cymoxanil commercialized in Peru. Common name a Commercial dose ppm b Metalaxyl 35% g/ 200 L Mancozeb 64% + Metalaxyl 8% 2-3 kg/ Ha or 50 g/ 20 L 200 Cupper hydroxide 46 % + Cymoxanil 6 % 0.5 kg / 200 L 150 Mancozeb 64 % + Cymoxanil 8 % 500 g / 200 L 200 Propineb 70 %+ Cymoxanil 6% Kg / Cylinder a Current active ingredients commercialized in Peru b 1 ppm = 1 mlg / L Mean EC 50 values (ppm( ppm) ) reported in this study Assays Mean EC 50 values (ppm) Mefenoxam Cymoxanil In vitro Detached leaf Whole plants

19 Conclusions: Baseline sensitivity established for Mefenoxam and cymoxanil in Peru High risk for resistance to Mefenoxam Low risk for resistance to cymoxanil

20 Thanks!!!!