EVALUATION OF FUNGICIDES FOR CONTROL OF BLACK SHANK IN TOBACCO S. Hollifield, P. Bertrand, J.M. Moore, D. Shew, J. Shealy, & M. Dowdy
BLACK SHANK OF TOBACCO Phytophthora nicotianae
PROBLEM: Black Shank of Tobacco - Caused by pathogen Phytophthora nicotianae - Affects tobacco plants at all growth stages - Disease begins on transplants once soil temperature is above 68 O F
PROBLEM: Black Shank of Tobacco - Symptoms include wilting, yellowing of leaves, and stem lesions - Root tips and wounds are the main site of infection - Black infected areas occur at the base of the stem and move upward - Easily spreads throughout a field
BLACK SHANK MANAGEMENT - RESISTANT VARIETIES - CROP ROTATION - NEMATODE CONTROL - IRRIGATION - CHEMICAL CONTROL
PRIOR TO 1980: No Effective Chemical Control
1980-1995 METALAXYL: A DUAL ISOMER PRODUCT (RIDOMIL 2E)
1996 - PRESENT MEFENOXAM: MORE ACTIVE ISOMER (RIDOMIL GOLD)
CHEMICAL CONTROL 1996-2015 RIDOMIL GOLD: 8.0 oz/acre Transplant Water (TPW) 8.0 oz/acre PLOWING as needed 16.0 oz/acre LAYBY
2014 SEVERE BLACK SHANK LOSSES - Devastating tobacco crop losses occurred, particularly in locations where Php genes had been utilized without chemical control. - High losses also occurred with applications of Ridomil Gold. - Growers concerned with Ridomil sensitivity.
RIDOMIL SENSITIVITY 30 FARM ISOLATES LANIER CO. (GF-318) ATKINSON CO. (K-346) COFFEE CO. (NC-196) ALL ISOLATES SENSITIVE (Dr. DAVID SHEW @ NCSU) Ridomil Resistance Not detected
2015 2015 PRESIDI PRESIDIO O PRESIDIO APPROV APPROVED ED
2015 2015 2016 PRESIDI PRESIDIO O ORONDIS APPROV APPROVED ED
OBJECTIVE - To evaluate and position new chemistry, in an effective black shank control program.
-Treatments: replicated three times - TPW Treatment : Designed in randomized complete block, running the entire length of field. 2016 & 2017 EXPERIMENTAL DESIGN - Layby Treatment: Modified Latin square, laid over the TPW treatments.
Data were collected visually based on wilted plants. With random checks for black lesions. 2016 & 2017 DATA COLLECTION
2016 TRIAL
MATERIALS & METHODS - Non-irrigated commercial tobacco field - History of Black Shank - Variety NC 196 - Planted March 24th
MATERIALS & METHODS Transplant Water Treatment (TPW): - Ridomil Gold - Check Layby Treatments: - Ridomil @ 16 oz. - Presidio @ 4 oz. - Orondis Gold - Check
2016 DATA COLLECTION - The trial was evaluated once, prior to layby - Three times post layby
2016 DATA TABLE - CK = Check - R = Ridomil Gold - O = Orondis Gold - P = Presidio
2016 BLACK SHANK CONTROL (BROOKS CO.) TREATMENT TPW X LAYBY % BLACK SHANK TREATMENT TPW X LAYBY % BLACK SHANK CK X CK 28.5a R X CK 24.9a CK X R 21.5a R X R 27.7a CK X O 18.3ab R X O 24.1a CK X P 7.4 b R X P 5.7 b
2016 BLACK SHANK CONTROL (ECHOLS CO.) TREATMENT TPW X LAYBY % BLACK SHANK TREATMENT TPW X LAYBY % BLACK SHANK CK X CK 66.0a R X CK 51.8a CK X P 51.0ab R X P 37.7 b CK X R 45.9 bc R X R 32.6 b CK X O 37.8 c R X O 29.8 b
2016 SUMMARY Black shank distribution in both plots was very uneven, which may account for inconsistent results.
2017 TRIALS
MATERIALS & METHODS - Non-irrigated commercial tobacco field - History of Black Shank disease - Variety NC 196 - Planted April 4th
MATERIALS & METHODS Transplant Water Treatment (TPW): - Orondis - Check Layby Treatments: - Ridomil @ 16 oz. - Presidio @ 4 oz. - Check
2017 DATA COLLECTION - The trial was evaluated once, prior to layby - Two times post layby
2017 BROOKS & ECHOLS COUNTY CONTROL TRIALS TREATMENT FINAL % BLACK SHANK TP WATER X LAYBY BROOKS CO. ECHOLS CO. CHECK X CHECK 14.8 a 16.6 a CHECK X PRESIDIO 9.2 b 9.0 b ORONDIS X CHECK 7.7 bc 8.4 b ORONDIS X RIDOMIL 6.9 c 6.8 b ORONDIS X PRESIDIO 6.4 c 5.4 b CHECK X RIDOMIL 6.1 c 8.4 b
2017 REGARDLESS OF LAYBY TREATMENT ORONDIS IN THE TPW WAS BETTER THAN THE CHECK (p=0.05) FINAL % BLACK SHANK TP WATER TRT BROOKS CO. ECHOLS CO. CHECK 10.0 a 11.3 a ORONDIS 7.0 b 6.8 b
2017 REGARDLESS OF TPW TREATMENT PRESIDIO & RIDOMIL AT LAYBY WERE EQUAL (p=0.05) AND BETTER THAN THE CHECK (p=0.05) FINAL % BLACK SHANK LAYBY TRT BROOKS CO. ECHOLS CO. CHECK 11.3 a 12.5 a PRESIDIO 7.8 b 7.2 b RIDOMIL 6.5 b 7.6 b
CONCLUSION Based on data collected at Georgia, N.C. State, and Virginia Tech
Most Effective Program - TPW: Orondis Gold (Ridomil plus Orondis mix) - FIRST PLOWING: Presidio @ 4 oz. or Ridomil Gold @ 8oz. as needed depending on farm history, rainfall since transplant, and years of rotation. -LAYBY:Apply the alternate fungicide product that was not used at plowing, Presidio @ 4oz/acre or Ridomil Gold @ 16oz/acre.
ACKNOWLEDGEMENTS Grower Cooperator Mr. Wavell Robinson And Estevan Salas Dr. Paul Bertrand, UGA Plant Pathologist Dr. J. Michael Moore, UGA Tobacco Agronomist Dr. David Shew, NCSU