TARGET SPOT IN COTTON POSSIBLE EMERGING DISEASE Heather Kelly, Assistant Professor Entomology and Plant Pathology Department WTREC, Jackson, TN University of Tennessee
Target Spot Foliar disease caused by fungal pathogen Corynespora cassiicola Recorded yield losses of 400+ lb lint/a Moisture and heat driven disease Develops after canopy closure Factors increasing risk of disease include: No- or strip-till cotton fields where cotton follows cotton Frequent showers and/or irrigation High nitrogen fertility levels (hits high-yield cotton hardest)
Distribution of Target Spot in Cotton Southern United States 2013 Corynespora cassiicola Host Range o Soybean o Sesame o Tomato o Cucumber o Beans o Hydrangea o Lantana
Target spot intensity and seed cotton yield of two cotton varieties - 2012 4500 Phytogen 499 DPL 1050 4500 4000 4000 Seed Cotton Yield lb/a 3500 3000 2500 Seed Cotton Yield lb/a 3500 3000 2500 2000 ~ 1000 lb/a Seed Cotton Loss 2000 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 Target Spot Intensity R 2 =0.37*** R 2 =0.05 NS Data from Dr. Austin Hagan, Auburn University Target Spot Intensity
Relationship between target spot intensity and seed cotton yield GC 2013 4500 Phytogen 499 4000 Deltapine 1252 4000 3500 Seed Cotton Yield lb/a 3500 3000 2500 2000 1500 1000 500 0 3000 2500 2000 1500 1000 500 0 1 2 3 4 5 6 7 1 2 3 4 5 6 7 R 2 =0.34*** Target Spot Intensity R 2 =0.22* Target Spot Intensity Data from Dr. Austin Hagan, Auburn University Seed Cotton Yield lb/a 1200 lb/a Seed Cotton Loss 600 lb/a Seed Cotton Loss
Data from Dr. Austin Hagan, Auburn University Target Spot Development on Phytogen 499 in 2012 and 2013 at Fairhope, AL Target Spot Intensity 10 9 8 7 6 5 4 3 2 1 # Headline Applications # Headline Applications 0 1 2 3 4 5 Target Spot Intensity 10 9 8 7 6 5 4 3 2 1 0 1 2 3 4
Yield Loss due to Target Spot What is known: Fungus survives on cotton debris Depends on variety Depends on location ~400+ lb/a loss Higher losses as yield increases Develops after canopy closure Late planted cotton at lower risk Some unknowns: Yield loss mechanism Range of yield loss for most cotton varieties Crop rotation Tillage practices Irrigation Geographic location
TARGET SPOT RISK ZONES Arkansas Louisiana Data from Dr. Austin Hagan, Auburn University
Target Spot Management Options Variety Fungicides
Seed Cotton Yield and % Defoliation 10 th WK BLOOM Gulf Coast 2012 Cotton variety Trial 1 Trial 2 % DEF Yield % /DEF Yield Phytogen 375 WFR 75 ab y 2959 ab 75 ab 3011 c-f Phytogen 499 WFR 82 a 2849 a-d 77 a 3118 b-f Phytogen 565 WFR 55 bcd 2904 abc 70 a-d 2989 c-f Deltapine 1044 B2RF 46 cd 2461 e 80 a 2774 efg Deltapine 1048 B2RF 55 bcd 3028 ab 55 f-j 3419 ab Deltapine 1050 B2RF 55 bcd 3056 ab 48 h-k 3097 b-f Deltapine 1137 B2RF 58 bc 2945 abc 60 e-i 3591 a Deltapine 1252 B2RF 50 cd 3111 a 38 jk 3268 abc FiberMax 1944 GLB2 60 bcd 2641 cde 63 b-g 3226 a-d Data from Dr. Austin Hagan, Auburn University
Cotton variety and fungicide impact Target Spot - 2103 Cotton Variety TS % DEF Boll Count # Seed Yield Phytogen 499 56 a 64.8 abc 4888 a Phytogen 565 45 b 75.3 ab 4610 ab DPL 1137 38 bc 76.3 a 4725 ab DPL 1050 21 d 60.8 bc 4304 b DPL 1252 33 c 57.4 c 4332 b Fibermax 1944 23 d 65.1 abc 4822 ab Stoneville 6448 38 bc 70.9 abc 4531 ab Fungicide Headline 9 fl oz 28 b 70.8 a 4703 a Control 45 a 63.6 b 4500 a Data from Dr. Austin Hagan, Auburn University
Data from Dr. Austin Hagan, Auburn University Cotton Variety Selection for Target Spot Management Variety reaction to target spot differs Phytogen 499 tends to suffer heaviest defoliation and may be at greater risk for sizable yield loss despite high yield potential (Risk/Reward) Most DPL, Stoneville, and Fibermax varieties are subject to less defoliation but can suffer yield losses under ideal conditions No variety has a high level of Target Spot resistance Have option of planting a more tolerant variety but need to consider yield potential
Fungicide Options Fungicide Rate/A Comments TWINLINE (metconazole + pyraclostrobin) Headline SC (pyraclostrobin) Quadris (azoxystrobin) 7-8.5 fl oz. 6-12 fl oz. 6-9 fl oz. Apply before disease development and continue on a 7- to 14-day schedule as needed to control disease. Do not make more than two consecutive applications of Twinline before alternating to a fungicide with a different mode of action. Apply prior to or at early stage of disease development and repeat after 7 to 14 days if conditions favor disease. Make no more than two consecutive applications of Headline SC. See label for additional information concerning resistance management with strobilurin fungicides. Apply at early bloom or early stages of disease development and repeat after 14 to 21 days as needed to control disease. Do not make more than two consecutive applications of Quadris. See label for additional information concerning resistance management for strobilurin fungicides.
Data from Dr. Austin Hagan, Auburn University Development of target spot on two cotton varieties as impacted by fungicides - 2013 Control Twinline L Twinline H Headline L Headline M Headline H Quadris L Quadris H 10 9 = Fungicide application dates Target Spot Intensity 8 7 6 5 4 3 2 1
Recommended Fungicides for Target Spot Control - 2012 Target Spot % Def Seed yield lb/a Variable Cotton variety means DPL 1050 27 b 3321 a Phytogen 499 68 a 3238 a Fungicide means Twinline 7.5 fl oz 42 b 3256 b Twinline 9 fl oz 42 b 3216 b Headline 6 fl oz 42 b 3400 ab Headline 9 fl oz 42 b 3474 a Quadris 6 fl oz 44 b 3205 b Quadris 9 fl oz 44 b 3377 ab Non-treated control 62 a 3156 b Data from Dr. Austin Hagan, Auburn University
Data from Dr. Austin Hagan, Auburn University Fungicides Compared for Target Spot Control and Yield Response on Two Cotton Varieties GC 2013 Treatments Target Spot Seed Cotton Yield Phytogen 499 DPL 1252 Control 52 a 2607 f 3096 b-e Twinline 7 fl oz (3x) 23 c 3291 ab 3222 ab Twinline 8.5 fl oz (3x) 33 bc 3394 a 3176 a-d Headline 6 fl oz (2x) 38 bc 2981 de 3233 a-d Headline 9 fl oz (2x) 33 bc 2904 ef 3165 a-d Headline 12 fl oz (2x) 35 bc 3268 abc 3279 ab Quadris 6 fl oz (3x) 40 ab 2981 de 3199 a-d Quadris 9 fl oz (3x) 35 bc 3015 cde 3371 a
Application Timing and Target Spot Control on Two Cotton Varieties - GC 2013 Fungicide and Rate Spray Timing (week of bloom) % Defoliation Phytogen 499 DPL 1252 AUDPC Seed Cotton Yield Control --- 73 a 27 cde 383 a 2894 b Headline 9 fl oz PHS + 2 nd wk 71 a 30 cd 362 a 3027 b Headline 9 fl oz 2 nd & 4 th wk 63 a 23 de 328 b 3107 b Headline 9 fl oz 4 th & 6 th wk 48 b 17 fg 305 cd 3342 a Headline 9 fl oz 6 th & 8 th wk 38 bc 17 fg 325 bc 3399 a Bravo WS 1.5 pt 2 wks (5x)* 48 b 20 efg 302 d 3422 a Bravo WS 1.5 pt + Heritage 9 fl oz 2 wks (5x)* 32 cd 16 g 278 e 3502 a *applications made PHS, 2 nd, 4 th, 6 th, and 8 th week of bloom Data from Dr. Austin Hagan, Auburn University
Recoverable Yield from Fungicides in Cotton Up to 300 lb/a lint cotton on selected cotton varieties, less on others (100-150 lb/a) Data from Dr. Austin Hagan, Auburn University
Summary Fungicide treatments can reduce target spot severity Few difference in efficacy Larger yield gains on Phytogen 499 than DPL 1252 Scouting-based and late rescue treatments will slow disease development and protect lint yields No major improvement in disease control or yield with full season fungicide programs Target Spot will most likely not have a significant impact on TN cotton in most years
Thank you for your attention Questions? youngkelly@utk.edu