Adjustments in the Tomato Spray Program in Tennessee Steve Bost Professor and Extension Plant Pathologist University of Tennessee
Control of early blight and bacterial spot, two of the most important diseases of tomato in Tennessee, was less than desirable. Pathogen resistance to control products may be responsible.
Early blight drives the tomato spray program, which has featured QoI s since Quadris was labeled in 1997.
Product & rate/75 gal Early Blight of Tomato 2013 Field Trial, Nashville This trial was a search for replacements for the Group 11 fungicides Quadris, Cabrio, and Tanos. Plants were sprayed 3 times at weekly intervals and evaluated 1 week after the 3 rd spray. Fontelis 20 fl oz Inspire Super Switch 14 oz Manzate 3 lb Bravo 2.75 pt Cabrio 12 oz Tanos 8 oz Quadris 6.2 fl oz Untreated check a a b b b c c c c 0 10 20 30 Leaf area affected (%) The results were used to guide the development of non-strobilurin-based spray programs.
Early Blight Spray Programs 2013 Trial, Highland Rim REC Four spray programs were evaluated on trellised, Mountain Glory tomatoes sprayed every 7-10 days, beginning 3 wks after planting; total of 10 sprays. Program Product Early blight % leaf area affected (final) Check none 88.0 a 1 Manzate alt. with Quadris 57.5 b 2 Manzate every application 23.3 c 3 Fontelis 10 fl oz* + Manzate + Kocide alt Manzate + Kocide 4 Inspire Super 1 pt then Manzate then Fontelis 1 pt then Manzate then repeat 0.3 d 0.1 d * The minimum labeled rate of Fontelis is 1 pt/acre.
Product & rate/75 gal Early Blight Fungicides 2014 Field Trial, Nashville This trial was a search for candidates for inclusion in a spray program. Plants were sprayed 3 times at weekly intervals and evaluated 1 week after the 3 rd spray. 7 7 3,9 7 9,12 M M 19 NC 11 Fontelis 20 fl oz Priaxor 8 fl oz Inspire Super 20 fl oz Endura 3.5 oz Switch 14 oz Bravo 2.75 pt Manzate 3 lb PhD 6.2 oz Double Nickel 1 qt Quadris 6.2 fl oz Untreated check a a a a a b b c c d d Do I really need to use anything more expensive than chlorothalonil or mancozeb? 0 10 20 30 40 50 Leaf area affected (%)
Early Blight Spray Programs 2014 Trial, Highland Rim REC Four spray programs were evaluated on trellised, Mountain Glory tomatoes sprayed every 7-10 days, beginning 5 wks after planting; total of 7 sprays. Program Product Early blight % leaf area affected (mid-harvest) Check none 91.3 a 1 Manzate alt. with Quadris every 3 rd application 66.3 b 2 Manzate every application 51.3 c 3 Fontelis 10 fl oz* + Manzate + Kocide every application 4 Inspire Super 1 pt then Manzate then Fontelis 1 pt then Manzate then repeat 2.9 d 4.3 d * The minimum labeled rate of Fontelis is 1 pt/acre.
Excellent control of early blight was provided by spray programs containing Inspire Super or Fontelis. Unsprayed check Program 4 Unsprayed check Program 4
Variety Early Blight Resistant Varieties 2014 Field Trial, Cheatham County, TSU AREC Determinate varieties with resistance to early blight were compared with the susceptible variety Mountain Glory. Quadris was applied once. Mountain Glory a Defiant BHN 964 bc b Iron Lady Mountain Fresh + Plum Crimson bc bc bc Mountain Merit bc Plum Regal c 0 20 40 60 80 Leaf area affected at mid-harvest (%)
Spray program for an early-blight resistant variety Mountain Merit Plateau REC, 2015 Spray program Early blight severity* (%) Mountain Glory Mountain Merit Unsprayed control 56.3 a 15.0 a Manzate each application 5.0 b 1.4 b Fontelis then Manzate then Inspire Super then Manzate then repeat sequence 0.6 b 0.2 b * Ratings were taken just prior to harvest. Early blight was later occluded by bacterial spot.
1 st spray 2 nd spray 3 rd spray 4 th spray Fontelis 1 pt chlorothalonil or mancozeb Inspire Super 1 pt chlorothalonil or mancozeb Repeat sequence until end of season
We are looking at the prevalence of QoI resistance.
Prevalence of Copper Resistance among Foliar Bacterial Pathogens of Tomato in Tennessee Jonathan Mixon Clavibacter michiganensis pv. michigansis (Cmm) Xanthomonas spp. (Xs) Pseudomonas syringae pv. tomato (Pst)
Needed an accurate method of determining copper resistance that was practical for a large-scale study Literature inconsistent on in vitro testing methods
In vitro copper resistance determination Variables tested (Chose a CuSO 4 concentration of 200 µg/ml) ph level choice of culture medium buffer concentration method of application of bacteria to medium culture incubation time effect of medium storage time
For Xs and Pst, used bioassays as guides. For Cmm, used sensitivity as the standard.
GROWTH (% OF CONTROL) Effect of medium ph on copper sensitivity for several Xanthomonas spp. isolates. Xanthomonas isolates ph 6.2 100 90 80 70 60 50 40 30 20 10 ph 6.5 ph 6.8 ph 7.o 0 451b (HR) 943 (MR) 1254 (MR) BL10 (HR) MA11-1 (S) MA11-2 (HR) HA11 (HR) FL87-2 (MR) ISOLATE (BIOASSAY RATING) 8-5 (S) 6-3 (S) 3-3 (MR) 3-20 a (MR)
Because of its known low-complexing activity, 2-(N-morpholino) ethanesulfonic acid (20 mm) was used to counteract the depressing effect of copper on medium ph.
Results A protocol was developed that included colony growth measurement on solid medium amended with CuSO 4 5H 2 O (200 µg/ml), expressed as a percent of that on a non-amended control. Plates were streaked by touching the edge of a sterile disposable loop one time to a culture on solid medium and making four streaks onto the test medium. Parameters were modified to produce copper sensitivity reactions that approximated in-vivo disease-control levels.
Results Factors causing greatest variability in cell resistance to copper were medium composition, medium ph, and age of prepared. Freshly-prepared sucrose peptone agar adjusted to ph 6.8 (Xs and Cmm) or 6.2 (Pst), provided copper sensitivity ratings that corresponded well with bioassay ratings. The potential sources of error in resistance determinations identified in this study underscore the need for attention to these parameters in all studies of resistance to copper.
Results: Pathogen Presence 195 acres were sampled 19 fields, 11 farms, 6 counties (Bledsoe, Grainger, Hamblen, Greene, Unicoi, Lauderdale) pathogens recovered from 166 samples (1 sample per acre) 162 were b-spot pathogens 4 were b-canker no b-speck (hot, dry seasons) 4 home gardens sampled 3 isolates were b-spot 1 isolate was b-canker
Results: Copper Resistance B-spot 154 resistant 8 sensitive (Lauderdale Co.) B-canker All 4 sensitive Home garden isolates 2 b-spot resistant, 1 sensitive 1 b-canker was sensitive
Jonathan also worked on developing a multiplex PCR protocol for simultaneous detection of all three pathogens.
Thank you