Vegetable Disease Update - Florida Ag Expo

Vegetable Disease Update 2009
Gary E. Vallad
Asst. Prof. of Plant Pathology
UF/IFAS Gulf Coast REC

• Bacterial spot –tomato& pepper
• Vegetable potpourri
– Maneb – mancozeb
– Bravo (chlorothalonil) label
– Late blight
– Topsin (thiophanate methyl)

Bacterial spot of tomato & pepper
• 4 phytopathogenic Xanthomonas spp.
– X. vesicatoria, X. euvesicatoria, X. perforans, X.
gardneri.
– In FL, X. euvesicatoria (pepper) & X. perforans
(tomato) predominate
– Numerous races exist (10 in pepper & 4 in
tomato); not all are in FL

Bacterial Spot Management:
– Cultural
– Biological
– Chemical

CULTURAL CONTROL
GOAL: reduce disease potential
– Destroy tomato debris
• Xanthomonas does not persist in soil
• Bury plant debris to ensure that it degrades
• Carryover to volunteer plants
• Seed supply & solanaceous weeds; questionable
– Begin with healthy, disease‐free seedlings
– Increase plant spacing to improve air movement
– Avoid working with wet foliage

BIOLOGICAL CONTROL
– Bacteriophages (bacteria‐specific virus)
• Successful in controlled trials
• Requires frequent applications & careful monitoring of
Xanthomonas population
• Organic production
– Biopesticides
• Biocontrol agents, plant extracts & phosphite salts
• Limited activity
• Inconsistent
• Organic production

CHEMICAL CONTROL
– Copper‐based fungicides
• numerous formulations
• resistance
– Antibiotics
• streptomycin sulfate
– Plant defense elicitors
• acibenzolar‐S‐methyl

CHEMICAL CONTROL
– Copper‐based fungicides
• Differences among Cu formulations
– Differences in ease of handling
– Little difference in activity
– Be careful with sticker‐spreaders

CHEMICAL CONTROL
– Copper‐based fungicides
• Differences among Cu formulations
– Differences in ease of handling
– Little difference in activity
– Beware of sticker‐spreaders…
• Cu tolerance among Xanthomonads
– Widespread among tomato & pepper isolates
– Assume that isolates are Cu‐tolerant

CHEMICAL CONTROL
– Copper‐based fungicides
• Differences among Cu formulations
– Differences in ease of handling
– Little difference in activity
– Beware of sticker‐spreaders…
• Cu tolerance among Xanthomonads
– Widespread among tomato & pepper isolates
– Assume that isolates are Cu‐tolerant
• Combine Copper with an EBDC (mancozeb / maneb)
– Increases Cu solubility…unclear whether this is the sole
benefit.

CHEMICAL CONTROL
– Antiobiotics
• Streptomycin sulfate
• Direct bacteriocidal activity
• Xanthomonads quickly develop resistance
• Only labeled for transplant production

CHEMICAL CONTROL
– Actigard (Acibenzolar‐S‐methyl)
• No direct bacteriocidal activity
• Stimulates plant defense responses
• Suppresses several foliar pathogens of tomato

Controls
STD
Gentamycin (3.5 lb)
Prophyt (2‐4 pt)
Prophyte (2‐4 pt) + Actigard
(0.25 oz)
Actigard (0.25 oz)
Actigard (0.75 oz)
Serenade Max (1 lb)
Omega Grow Plus (2% v/v)
SeaCide (1% v/v)
HMO 736 (14 oz)
Citrex (1 ml/L)
Kasumin (1 qt/50gal)
Tiadanil (500 ppm)
Taegro (3.5 oz)
1200
1000
800
600
400
200
0
Fall 2008 –Tomato Bacterial Spot Trial
AUDPC (95% CI)

Controls
STD
Gentamycin (3.5 lb)
Prophyt (2‐4 pt)
Prophyte (2‐4 pt) + Actigard
(0.25 oz)
Actigard (0.25 oz)
Actigard (0.75 oz)
Serenade Max (1 lb)
Omega Grow Plus (2% v/v)
SeaCide (1% v/v)
HMO 736 (14 oz)
Citrex (1 ml/L)
Kasumin (1 qt/50gal)
Tiadanil (500 ppm)
Taegro (3.5 oz)
1200
1000
800
600
400
200
0
Fall 2008 –Tomato Bacterial Spot Trial
AUDPC (95% CI)

Controls
STD
Gentamycin (3.5 lb)
Prophyt (2‐4 pt)
Prophyte (2‐4 pt) + Actigard
(0.25 oz)
Actigard (0.25 oz)
Actigard (0.75 oz)
Serenade Max (1 lb)
Omega Grow Plus (2% v/v)
SeaCide (1% v/v)
HMO 736 (14 oz)
Citrex (1 ml/L)
Kasumin (1 qt/50gal)
Tiadanil (500 ppm)
Taegro (3.5 oz)
1200
1000
800
600
400
200
0
Fall 2008 –Tomato Bacterial Spot Trial
AUDPC (95% CI)

11000
10000
9000
8000
7000
6000
5000
Spring 2009 – Tomato Bacterial Spot Trial
AUDPC (95% CI)
EXPT 1
EXPT 1 + Penncozeb, 2 lb
EXPT 2, 3pt
EXPT 2, 2pt
EXPT 2, 1pt
EXPT 2, 3pt; Penncozeb, 2lb
EXPT 2, 2pt; Penncozeb, 2lb
EXPT 2, 1pt; Penncozeb, 2lb
Cuprofix, 3lb; Penncozeb, 2lb
Cuprofix, 1.5lb; Penncozeb,
1.25lb
Actigard, 0.75oz; Cuprofix, 1.5
lb; Penncozeb, 2lb
Control

11000
10000
9000
8000
7000
6000
5000
Spring 2009 – Tomato Bacterial Spot Trial
AUDPC (95% CI)
PDS (250:1)
PDS (250:1); Cuprofix, 3lb;
Penncozeb, 2lb
PDS (250:1); Cuprofix, 1.5lb;
Penncozeb, 1.25lb
Cuprofix, 3lb; Penncozeb, 2lb
Cuprofix, 1.5lb; Penncozeb,
1.25lb
Actigard, 0.75oz; Cuprofix, 1.5
lb; Penncozeb, 2lb
Control

% Foliage with Disease Symptoms
100
90
80
70
60
50
40
30
20
10
0
Spring 2008 ‐ Target Spot & Early Blight
P TRT < 0.0001
P TIME < 0.0001
54 DAT 60 DAT 80 DAT
Days After Transplanting (Inoculated 43 DAT)
Control
Bravo Ultrex
2 pt/A*
Quadris
15.4 floz/A*
Actigard
0.75 oz/A; 8 apps.
*Trts rotated with
Cuprofix (3 lb) and
Penncozeb (2lb)

Ongoing trials:
– Evaluate application rates and frequency of
Actigard
• Lower label rates may be as effective as high rates
• Frequency; weekly/biweekly
• Only labeled for bacterial spot & speck control on
tomatoes and chili peppers.
• Testing bell peppers (Fall 2009)
• Expanded label for cucurbits – currently testing in PM &
DM trials (Fall 2009).

MANEB & MANCOZEB UPDATE:
– UPI voluntarily cancelled registration of maneb
with EPA (Dec 31 st –stop selling)
– EPA review of a proposed crop expansion of
certain mancozeb labels (Dow & DuPont) was
postponed until March 2010 (tentative)
– Expansion of Bravo (chlorothalonil) labels; not an
acceptable substitute
– Assess maneb needs and availability with local
distributor prior to Dec 31 st

Crop
REGISTRATION STATUS AS OF OCTOBER 2009
Chlorothalonil
Maneb Mancozeb (Bravo)
Broccoli Yes No Yes
Cabbage Yes No Yes
Lettuce Yes No No
Peppers Yes No Yes
Pumpkins Yes No Yes
Squash, winter Yes No Yes
Beans, dry Yes No Yes
Brussels sprouts Yes No Yes
Cauliflower Yes No Yes
Chinese cabbage Yes No Yes
Collards Yes No No
Endive Yes No No
Eggplant Yes No Yes
Kale Yes No No
Kohlrabi Yes No Yes
Mustard greens Yes No No
Onion, green Yes No Yes
Turnip tops Yes No No

Late Blight Update:
• Outbreak this summer in Northeast and
Midwest US
• Ideal weather conditions prevailed (cool and
damp)
• Suspected link to wholesale transplants
produced in AL and MS
• Novel isolate

• Loss of Topsin M WSB (thiophanate‐methyl)
– Section 18 emergency exemption has been
granted for the past couple of years.
– Control of white mold, Sclerotinia sclerotiorum, on
tomato & pepper
– Historically a severe problem in Palm Beach Co.
– EPA rejected latest request; one of TMs primary
metabolite carbendazim is used in paints,
adhesives & caulks.

Thank You!