Table 1.
Composition of four ready-to-use dual mixtures of oxathiapiprolin.
Fig 1.
Minimal inhibitory concentration (MIC) values of oxathiapiprolin in preventive and curative application against late blight induced by Israeli isolates of Phytophthora infestans, in detached tomato leaves.
A- Detached leaflets were treated with oxathiapiprolin of 0.00001–10 ppm active ingredient (ai) on lower leaf surface and thereafter spray-inoculated with each of 106 isolates of P. infestans. B- Detached leaflets were first inoculated with each of 90 isolates of P. infestans on lower leaf surface and at 1 day after inoculation were treated with oxathiapiprolin of 0.00001–10 ppm ai. Percent of leaf area showing sporulation of the pathogen was recorded at 7 days post-inoculation (dpi).
Fig 2.
Efficacy (A-E) and microscopy (F-H) of curative application (1 dpi) of oxathiapiprolin on late blight development in detached tomato leaves. Detached tomato leaflets were drop-inoculated on their lower leaf surface with sporangia of P. infestans and sprayed with oxathiapiprolin at 1 dpi. Leaf discs were removed at 2 dpi for microscopic observations. Lesion size and sporangial yield were determined at 4 dpi. A- Lesion size. B- Sporangial yield per leaflet. C, F- Sporulation of P. infestans in control leaflets. D, G- Response of leaflets treated with 1-ppm ai oxathiapiprolin. E, H- Response of leaflets treated with 10-ppm ai oxathiapiprolin. Note the necrosis induced by oxathiapiprolin.
Fig 3.
Preventive activity of oxathiapiprolin against late blight induced by 12 Israeli isolates of P. infestans in intact tomato plants.
A- Percent of leaf area blighted for each isolate at 4 dpi. Note that minimal inhibitory concentration (MIC) = 1 ppm ai. B- Percent of leaf area blighted for each isolate at 8 dpi. Note that MIC≥10-ppm ai. C- Mean dose-response curves for 12 isolates at various time intervals after inoculation. D- ED 90 values derived from the values in presented C.
Fig 4.
Preventive (A and B) and 1 dpi curative (C and D) activities of oxathiapiprolin (OXPT), chlorothalonil (CHT), azoxistrobin (AZ), mandipropamid (MPD), mefenoxam (MFX), and their dual mixtures OXPT+CHT, OXPT+AZ, OXPT+MPD, and OXPT+MFX against late blight induced by isolate 164 of P. infestans in intact tomato plants. A, C- Percent of leaf area blighted at 10 dpi. B, D- Effective dose 90% values (ED 90) calculated from the 10 dpi data. Different letters in A and C indicate significant differences between means (t-test, α = 0.05). Note the outperformance of OXPT+MFX.
Fig 5.
Comparison between preventive (blue lines) and curative (red lines) activity of OXPT, CHT, AZ.
MPD, MFX and their dual mixtures OXPT+CHT, OXPT+AZ, OXPT+MPD and OXPT+MFX in controlling late blight induced by isolate 164 of P. infestans in intact tomato plants. Note the reduced efficacy of all fungicides in curative application and the outperformance of OXPT+MFX.
Fig 6.
Translaminar activity of OXPT, CHT, AZ.
MPD, MFX and their dual mixtures OXPT+CHT, OXPT+AZ, OXPT+MPD, and OXPT+MFX against late blight induced by isolate 164 of P. infestans in detached tomato leaves. A- Percent sporulating leaf area. UU = upper leaf surface treated upper leaf surface inoculated. UL = upper leaf surface treated lower leaf surface inoculated. Different letters indicate significant differences between means (t-test, α = 0.05). B and C- ED 90 values derived from A for UU or UL treatments.
Fig 7.
The enhancing effect of soluble concentrate (SL) blind formulation (BF) on the curative activity of OXPT against late blight induced by isolate 164 of P. infestans at 1 dpi (A) and 2 dpi (B). OXPT+BF = OXPT and BF mixed at a ratio of 1+3 by weight. Note the enhanced activity of OXPT+BF relative to OXPT, and of OXPT+MFX relative to OXPT+BF. Different letters indicate significant differences between means (t-test, α = 0.05).
Fig 8.
Systemic protection of the newly developed leaves of potted tomato plants from late blight.
OXPT, CHT, AZ, MPD, MFX, OXPT+CHT, OXPT+AZ, OXPT+MPD, or OXPT+MFX were sprayed at 100-ppm ai onto 5-leaf plants. The plants were inoculated with isolate 164 of P. infestans 17 days later, at the 10-leaf stage. A- Percent of leaf area blighted at 7 dpi on the five bottom-treated leaves. B- Percent of leaf area blighted at 7 dpi on the top five newly grown leaves. Different letters above columns indicate significant differences between means (t-test, α = 0.05). Note that OXPT+MFX provided the best systemic protection.
Fig 9.
Systemic protection of tomato plants against late blight by root treatment with OXPT, CHT, AZ, MPD, MFX, OXPT+CHT, OXPT+AZ, OXPT+MPD, or OXPT+MFX.
One ml of fungicide(s) suspension of various doses was applied to the soil around the stem base and one-day later plants were inoculated with isolate 164 of P. infestans. A- Percent of leaf area blighted taken at 7 dpi. Different letters indicate significant differences between means (t-test, α = 0.05). B- The appearance of inoculated plants at 7 dpi. Note the high protection provided by 100-ppm ai of OXPT or OXPT+MFX.
Fig 10.
Systemic protection of tomato plants against late blight by seed treatment with OXPT, MFX, OXPT+AZ, OXPT+MPD, or OXPT+MFX.
A- Plants grown from treated seeds were inoculated at the 4-leaf stage. B- Plants grown from treated seeds were inoculated at the 6-leaf stage. Different letters above columns indicate significant differences between means (t-test, α = 0.05).
Fig 11.
Control of late blight in tomato by OXPT, AZ, MPD, MFX and their dual mixtures under field conditions.
Tomato plants were planted in the field on 25.9.2016, in two replicate plots of 1 m2, 6 plants per plot. One month later, plants were sprayed once with fungicides. One day later, plants were artificially inoculated with a mixture of 30 MFX-insensitive isolates of P. infestans. Percent leaf area blighted scores from each plant were taken at 4, 6, 7, 11, and 14 dpi. A- Area under disease progress curve (AUDPC) for each dose/fungicide. B- Percent of season-long protection provided by each fungicide. Different letters on columns indicate significant differences between treatments (t-test, α = 0.05). Note the outperformance of OXPT+MFX.
Fig 12.
Control of late blight in tomato by OXPT, AZ, MPD, MFX, and their dual mixtures under field conditions.
Tomato plants were planted in the field on 1.10.2016 in two replicated plots of 1 m2, 5 plants per plot. One month later, plants were sprayed once with fungicides. One day later, plants were artificially inoculated with the MFX-insensitive isolate 164 of P. infestans. Percent leaf area blighted scores were taken at 6, 10, and 13 dpi. A- AUDPC value for each dose/fungicide. B- Percent of season-long protection provided by each fungicide. Different letters on columns indicate significant differences between means (t-test, α = 0.05).
Fig 13.
Control of late blight in tomato by OXPT, CHT, AZ, MPD, MFX, and their dual mixtures under field conditions.
Tomato plants were planted in the field on 1.12.2017 in two replicate plots of 1 m2, 5 plants per plot. After 3 weeks, plants were sprayed once with fungicides. On the same day, the plants were artificially inoculated with a mixture of five MFX-insensitive isolates of P. infestans. Percent leaf area blighted scores were taken at 7, 10, 15, and 17 dpi. A- AUDPC values for each dose/fungicide. B- Percent of season-long protection provided by each fungicide. Different letters on columns indicate significant differences between means (t-test, α = 0.05).
Fig 14.
Control of late blight in tomato by OXPT, CHT, AZ, MPD, MFX, and their dual mixtures under field conditions.
Tomato plants were planted in the field on 1.2.2018 in two replicate plots of 1 m2, 5 plants per plot. After 3 weeks, plants were sprayed once with fungicides. On the same day, the plants were artificially inoculated with a mixture of five MFX-insensitive isolates of P. infestans. Percent leaf area blighted scores were taken at 9, 12, 15, and 19 dpi. A- AUDPC values for each dose/fungicide. B- Percent of season-long protection provided by each fungicide. Different letters on columns indicate significant differences between means (t-test, α = 0.05).