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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