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Melon Disease Upddate:
Diagnosis and Control
Thomas TuriniUniversity of California Cooperative Extension
Fresno County
Melon Disease Topics
• Vine decline– Monosporascus root rot– Charcoal rot
• Foliar diseases– Powdery mildew
• Diseases caused by viruses– Potyviruses – Cucurbit yellow stunting disorder virus
Vine Decline
Monosporascus cannonballus Perithecia
Monosporascus cannonballus Perithecia
Monosporascus cannonballus Perithecia
Monosporascus cannonballus Perithecium
and ascospores
Monosporascus cannonballus ascospores and asci
Monosporascus cannonballus Environmental Requirements
• Optimum temperatures for fungal growth: 77o to 95oF
• Plant stress is required for vine decline
Inoculum Production After Harvest, 2000
0
10
20
30
40
50
60
70
0 1 2 3
Weeks after harvest
Roo
ts w
ith p
erith
ecia
(%)
cbc
b
a
Stanghellini et. al. 2001. Plant Disease
Effect of Metam Sodium on Perithecia Production, 2000
010203040506070
0 1 2 3
Weeks after harvest
Root
s w
ith p
erith
ecia
(%)
Non-treated check metam sodium
cbc
b
a
B A A A
Effect of Cultivation on Perithecia Production, 2000
010203040506070
0 1 2 3
Weeks after harvest
Root
s w
ith p
erith
ecia
(%)
Non-treated check Cultivation
c bc
b
a
B A A A
Stanghellini et. al. 2001. Plant Disease
Management under SJV conditions
• During the warmer times of the year, avoid planting melons in fields known to be infested with this pathogen.
• If detected, destroy roots after harvest to prevent increase of inoculum levels in the soil.
Charcoal Rot - Macrophomina phaseolina
Macrophomina phaseolina Environmental Requirements
• Disease incidence is favored by plant water stress and high temperatures.
Macrophomina phaseolina Environmental Requirements
• Disease incidence is favored by plant water stress and high temperatures.
• Optimum soil temperature for infection is approximately 86 ºF,
Charcoal Rot Control
• Avoidance of stressing the plants reduces the occurrence of charcoal rot
Charcoal Rot Control
• Avoidance of stressing the plants reduces the occurrence of charcoal rot
• Soil fumigants, solarization and deep plowing are ineffective, and crop rotation is impractical due to the extremely wide host range.
Powdery mildew on cantaloupe Podosphaera xanthii or Sphearotheca fuliginea
W. Gärtel
Conidia in chains
Conditions Favoring Powdery Mildew Development
• Temperature - Optimum is 81 ºF.
• Humidity requirement - >46%
Host Range of P. xanthii
• Cantaloupes, casaba and honeydew (Cucumis melo)
• Cumbers (Cucumis sativus)
• Various squash: Banana squash (Cucurbita maxima), Butttenut squash (C. moschata), and Zucchini, yellow squash, pumpkin and ornamental gourd (C. pepo)
• Watermelon (Citrullus lanatus)
• Fungicides
• Resistant varieties
Control of Powdery Mildew of Melons
FRAC Code
Group Name Trade Names (common names)
Resistance Potential
11 Quinone outside Inhibitors(QoI) or Strobilurins
Cabrio (pyraclostrobin) , Flint (trifloxystrobin), Quadris (azoxystrobin),Sovran (kresoxy methyl)
High
1 Methyl Benzimidazole Carbamates
Topsin (thiophanate-methyl) High
7 Carboxamides Endura (boscalid) Medium
3 DeMethylation Inhibitors (Class I of the Sterol biosynthesis inhibitors)
Procure (triflumizole), Rally (myclobutanil)
Medium
13 Quinolines Quintec (quinoxyfen) Medium
M2 Inorganic – Sulfur Various LowM5 Chloronitriles
(pthalonitriles)Various (chlorothanlonil) Low
From Fungicide Resistance Action Committee – Updated 2010 http://www.frac.info/frac/index.htm
Methods
• West Side Research and Extension Center
• Casaba cv. ‘Golden Beauty’
Experimental Design
• Randomized Complete Block• Replications: 5• Plot Dimensions: 1 bed X 25 ft• Five feet between plots within a row• One planted bed between treated rows
Fungicide Application Details
• Application method: CO2 pressurized backpack sprayer• Spraying pressure: 30 psi• Spray volume per acre: 30 gallons• Surfactant: Induce 0.25% by volume
Plant date
Application dates Mildew present
Evaluation dates
2008 17 Jun 26 Aug, 3 Sep 25 Aug 2, 11 and 19 Sep
2009 23 Jun 6, 17, 25 Aug, 2 Sep 28 Aug 31 Aug, 8 and 17 Sep
Closely read all labels before writing a recommendation
• Not all materials tested are currently registered.
• Some materials have restrictions that could influence practicality of use in some situations.
0 2 4 6 8 10 12 14 16 18
Untreated
Quintec 6fl oz
Quadris
Inspire Super 20floz
Sovran
Rally
Prcur8f oz
Mcrtl(1)/Tpsn+Mcrtl(2,3)
Quadris+KBS
Microthiol Disperss
Quadris + KTS
Prcr 8f loz(1,3)/Qntc6floz(2)
Pinpoint
Prcr4floz+Qntc4floz
Inspire Super 14 f l oz
Sovran + Endura
Endura
Leaf surfaces with PM (%)
aa
bb
b
bbbb
bb
b
bbb
bb
19 Sep 2008(lower leaf surface)
0 5 10 15 20 25 30
Untreated
Quintec 6floz
Quadris
Rally
Prcr 8f loz(1,3)/Qntc6floz(2)
Inspire Super 20floz
Prcur8f oz
Sovran
Pinpoint
Prcr4floz+Qntc4floz
Quadris+KBS
Endura
Inspire Super 14 f l oz
Mcrtl(1)/Tpsn+Mcrtl(2,3)
Quadris + KTS
Microthiol Disperss
Sovran + Endura
Leaf surfaces with PM (%)
ab
ccdcd
cdcdcd
cd
cdcdcd
cd
cdd
dd19 Sep 2008
(upper leaf surface)
Summary
• Under the conditions of this trial, materials that provided control included
– Procure 480SC, Rally 40SP– Quadris, Sovran – Endura– Pinpoint (V10118)– Microthiol Dispress– Inspire Super (difenoconazole:DMI + cyprodinil:Anilino-
Pyrimines)
• Quintec performance was poor under these conditions
0 2 4 6 8 10 12 14
Untreated Control
Bravo 2 pts
Microthiol 5 lbs
Regalia 0.5% + Bravo WS 1 pt
Quadris Top (1, 3)/Bravo (2, 5)
Regalia 1%
Regalia 0.5%+Rally 40 2.5 oz
Inspire Super(1, 2, 5)/Bravo(3)
Rally 40 5.0 oz
GWN-4617 3.4 oz+Gavel 2.0 lbs (4,6)
BAS 56003 15.37 fl oz+BAS 91500F 7.0 f l oz
GWN-4617 3.4 oz (4, 6)
BAS 56003 10.24 fl oz+BAS 91500F 5.0 f l oz
GWN-4617 3.4 oz (4)/Quadris 15.5 f l oz (6)
GWN-4617 3.4 (4, 5)
Quintec 250SC 6 f l oz
GWN-4617 3.4 oz
Luna 4.0 oz
Leaf surfaces with PM (%)
aab
abcabc
abc
bcdebcdbcd
bcd
ef
cde
de
f
cde
ff
ef
8 Sep 2009(lower leaf surface)
def
0 5 10 15 20 25 30 35
Untreated Control
Regalia 1%
Regalia 0.5%+Rally 40 2.5 oz
Rally 40 5.0 oz
Regalia 0.5% + Bravo WS 1 pt
Quadris Top (1, 3)/Bravo (2, 5)
Bravo 2 pts
GWN-4617 3.4 oz (4, 6)
GWN-4617 3.4 oz+Gavel 2.0 lbs (4,6)
GWN-4617 3.4 oz (4)/Quadris 15.5 f l oz (6)
GWN-4617 3.4 (4, 5)
Microthiol 5 lbs
Inspire Super (1, 2, 5)/Bravo (3)
BAS 56003 15.37 fl oz+BAS 91500F 7.0 f l oz
BAS 56003 10.24 fl oz+BAS 91500F 5.0 f l oz
Quintec 250SC 6 f l oz
Luna 4.0 oz
GWN-4617 3.4 oz
Leaf surfaces with PM (%)
ab
bc
bcd
bc
cde
bcd
bc
bcdbcd
bcdebcde
bcd
bcb
bc
e8 Sep 2009(upper leaf
surface)de
Summary, 2009
• Under the conditions of this trial, currently unregistered materials were among the best performing (GWN-4617, Luna and numbered BAS materials).
• Quintec performance was among the best when applied preventatively.
MELON DISEASES CAUSED BY VIRUSES
Potyviruses
• Aphid transmitted viruses• Host range
– all three infect cucurbits– WMV infects goosefoot, lambsquarters,
Russian thistle, various legumes and cheeseweed
Watermelon mosaic virus
Papaya ringspot virus
Zucchini yellow mosaic virus
Symptoms on Watermelon Fruit early Oct 2009
WMV and PRSV detected
General Potyvirus symptoms
Watermelon Mosaic Virus
Zucchini Yellow Mosaic Virus
Management
• Insecticide applications are not recommended for control of potyviruses
Imperial Valley: Cucurbit yellow stunt disorder virus (CYSDV)
21 Oct 2006
Imperial Valley: CYSDV 3 Nov 2006
Transmission of CYSDV
• Silverleaf whitefly (Bemisia tabaci biotype B)– Semipersistent:
• acquired in as little as two hour of feeding• transmitted for 7 days
• No evidence that it is seed-borne
Host Range of CYSDV• Cucurbits (muskmelon, watermelon, cucumber,
pumpkin and squash)• Alfalfa, lettuce, bean (Phaseolus vulgaris), alkali
mallow (Sida hederacea) and Wright's groundcherry (Physalis wrightii). *
• Transmission tests demonstrated that lettuce, snap bean, alkali mallow, Wright's groundcherry, and buffalo gourd (Cucurbita foetidissima). *
* Wintermantel, William M. Hladky, Laura L. Cortez, Arturo A. Natwick, Eric T. 2009. Plant disease. v. 93, no. 7 p. 685-690.
Aphid-borne yellows virus
Acknowledgements• California Melon Research Board
• PCAs and growers
• Staff at UC WSREC
• Robert Gilbertson
• William Wintermantel
• Michael Stanghellini
Downy Mildew –Pseudoperonospora cubensis
Downy Mildew –Pseudoperonospora cubensis
Pseudoparonospora cubensis
Photo by Gerald Holmes
Damage
Photo by Frank Laemlen
Fusarium Wilt - Fusarium oxysporum f. sp. melonis
Photo by Mike Davis
Fusarium wilt of watermelon Fusarium oxysporum f. sp. niveum
Photo by Mike Davis