Four Years of Downy Mildew in Indiana: Field Trials and More. Daniel S. Egel Southwest Purdue Ag Center Vincennes, IN

Outline Downy mildew introduction Symptoms Introduction of fungicides 2005/6 field trials Management recommendations

Downy Mildew Overwintering pattern

Recent Downy Mildew History First observation of downy mildew Year Date Crop 2002 and earlier Approx. every 5 years in late Aug/early Sept. 2003 July 22 2004 August 13 2005 August 9 2006 July 18 Usually pumpkin Watermelon Pumpkin Pumpkin Cucumber

Outline Downy mildew introduction Symptoms Introduction of fungicides 2005/6 field trials Management recommendations

Pumpkin

Watermelon

Cucumber

Muskmelon

Pumpkin Muskmelon Watermelon Cucumber

Outline Downy mildew introduction Symptoms Introduction of fungicides 2005/6 field trials Management recommendations

Contact Fungicides kills fungi with which it comes into direct contact on plant surface. Contact fungicides do not move within the plant. Multiple modes of action.

Systemic fungicides move within the plant, usually toward the tip of the plant, so that existing fungi may be killed. Often have only one mode of action-resistance may occur.

Fungicide resistance and FRAC codes

Contact Fungicides Fungicides Resistance Risk Alternation or tank mix Other diseases Bravo, Echo, Equus (chlorothalonil) Dithane,, Manzate, Penncozeb (mancozeb) Maneb, Manex (maneb) Kocide,, Champ, Cuprofix (copper hydroxide/sulfate) Multiple modes of action (M)- resistance unlikely Can be used in alternation with systemic fungicides- alternation not necessary for resistance Effective against a broad range of diseases.

Fungicides for downy mildew management- Contact fungicides- FRAC group M, resistance unlikely Many diseases/season long Relatively inexpensive Good rotational partners Moderate downy mildew control

Systemic fungicides in group 11 Fungicides Amistar, Quadris (azoxystrobin) Cabrio (pyraclostrobin) Flint (trifloxystrobin( trifloxystrobin) Pristine (boscalid, pyraclostrobin) Quadris Opti (azoxystrobin, chlorothalonil) Reason (fenamidone( fenamidone) Resistance Risk 11 medium- high- Cross resistance possible. 11 & M Medium-high Alternation or tank mix Alternation required, tank mix recommended Premix, alternation required 11, high Alternation Other diseases Label may include powdery mildew, black rot. See above Alternaria

Fungicides for downy mildew management- Systemic fungicides in group 11 Season long control for several diseases High chance of cross resistance Tank mix with contact when DM threatens

Specialized Systemic fungicides for downy mildew I Fungicide Acrobat, Forum (dimethomorph) Previcur Flex (propamocarb) Reason (fenamidone( fenamidone) Ranman (cyazofamid( cyazofamid) Ridomil (mefenoxam) Resistance risk (FRAC) Alternation or tank mix 15, medium Tank or premix 28, low- medium Alternation 11, high Alternation 21, medium- high Alternation 48 (high) Alternation Other diseases With premix Pythium Alternaria Phytophthora Depends on premix

Specialized Systemic fungicides for downy mildew II Fungicide Tanos (cymoxanil, famoxadone) Curzate (cymoxanil) Resistance risk (FRAC) 27, 11 High 27, medium- high Alternation or tank mix Both required Tank mix -- Other diseases Phytophthora Alternaria

Fungicides for downy mildew management- Specialized systemic fungicides Several FRAC groups Chance of resistance variable Primarily for downy mildew Best used when downy mildew in area

Premixes-contact & systemic Fungicide Resistance Risk Alternation or tank mix Other diseases Ridomil Bravo Gold (mefenoxam, chlorothalnil) FRAC 48, M. High Alternation Black rot Quadris Opti (azoxystrobin, chlorothalonil) 11 & M Medium- high Premix, alternation required Several Gavel (mancozeb, zoxamide) FRAC 22, Low- medium No Alternaria

Premixes Less chance of resistance Contact may control additional disease

Outline Downy mildew introduction Symptoms Introduction of fungicides 2005/6 field trials Management recommendations

2,000 1,600 1,200 800 400 0 a b 2005 Field Trial 2005 Field Trial b b c cd cd d d Flex 1.2 qt Previcur Previcur Flex 1.2 qt Manex Manex 1.6 1.6 qt qt Manex 1.6 1.6 qt qt Tanos Tanos 8 oz+manex oz+manex 1.6 1.6 pt pt Curzate Curzate 3.2 3.2 Amistar Amistar 5 oz/ oz/manex Manex 1.6 1.6 qt qt 1.6 qt Curzate Curzate 3.2 3.2 oz/ oz/manex Manex 1.6 qt Curzate Curzate 5.0 5.0 oz/ oz/manex Reason Reason 5.5 5.5 fl fl oz/ oz/manex Manex 1.6 1.6 qt qt Pristine Pristine 18.5 18.5 oz/ oz/manex Manex 1.6 1.6 qt qt Manex Manex 1.6 1.6 4F 4F 1.6 1.6 qt qt Non Non-treated treated Disease severity Disease severity

4,000 3,000 2,000 1,000 0.00 c ab bc 2005 Field Trial 2005 Field Trial a a ab ab ab ab Flex 1.2 qt Previcur Previcur Flex 1.2 qt Manex Manex 1.6 1.6 qt qt Manex 1.6 1.6 qt qt Curzate Curzate 5.0 5.0 oz/ oz/manex Manex 1.6 1.6 qt qt 1.6 pt 3.2 oz/manex Tanos Tanos 8 oz+manex oz+manex 1.6 pt Curzate Curzate 3.2 3.2 Amistar Amistar 5 oz/ oz/manex Manex 1.6 1.6 qt qt Manex 1.6 1.6 qt qt Curzate Curzate 3.2 oz/ Pristine Pristine 18.5 18.5 oz/ oz/manex Reason Reason 5.5 5.5 fl fl oz/ oz/manex Manex 1.6 1.6 qt qt Manex Manex 1.6 1.6 4F 4F 1.6 1.6 qt qt Non Non-treated treated Pounds per Acre Pounds per Acre

1,400 1,000 600 200 0 a cd cde 2006 Field Trial 2006 Field Trial cde de de de e e Previcur Previcur Flex/Bravo Flex/Bravo 2 pt. pt. Ranman 2.75 2.75 oz/bravo oz/bravo 1.5 1.5 pt. pt. Ranman Flex 1.2 pt Ridomil Ridomil MZ MZ 2.5 2.5 lb lb Quadris Quadris Opti Opti 3.2 3.2 pt pt Tanos Tanos 8 oz+bravo oz+bravo 2 pt pt Bravo Bravo 2pt+Curzate 2pt+Curzate 3.2 3.2 oz oz Ranman Ranman 2.1 2.1 oz/bravo oz/bravo 1.5 1.5 pt. pt. Sonata 2 qt+previcur qt+previcur Flex 1.2 pt Manex Manex 1.6 1.6 Bravo Bravo WS WS 2 pt pt Sonata 2 Cabrio Cabrio 12 12 oz/bravo oz/bravo 2 pt pt Disease severity Disease severity Non-treated Non treated

Outline Downy mildew introduction Symptoms Introduction of fungicides 2005/6 field trials Management recommendations

Downy Mildew Favorites Fungicide Previcur Flex (propamocarb) Ranman (cyazofamid( cyazofamid) Tanos (cymoxanil, famoxadone) Curzate (cymoxanil) Gavel (mancozeb, zoxamide) Resistance risk (FRAC) 28, low- medium 21, medium- high 27, 11 High 27, medium- high 22, Low- medium Alternation or tank mix Alternation Alternation Both required Tank mix -- No Other diseases Pythium Phytophthora Phytophthora Alternaria Alternaria

Downy mildew Scout fields and follow epidemic Apply contact fungicide weekly if disease threatens or mix contact & systemic; 7-107 days schedule Apply specialized systemics only if DM observed in area. Cultural management

Pumpkin fungicide schedule Specialized systemics Systemics: : groups 11, 3, 1 Contact Fixed copper June July August September Oct Bacterial spot Powdery Mildew Black rot/plectosporium Downy mildew

2005 research trial Treatment, rate/a Non-treated AUDPC 1,749.25 a Manex 4F, 1.6 qt 1,290.50 b Reason 500SC, 5.5 fl oz Manex 4F, 1.6 qt 1,259.00 b Pristine 38WG, 18.5 oz Manex 4F, 1.6 qt 1,228.25 b Amistar 80WP 5 oz Manex 4F, 1.6 qt 1,046.00 c Tanos 50WDG, 8 oz + Manex 4F, 1.6 qt Curzate 60DF, 3.2 oz 958.00 cd Curzate 60DF, 3.2 oz + Manex 4F, 1.6 qt 936.50 cd Curzate 60DF, 5 oz + Manex 4F, 1.6 qt 841.75 d Previcur Flex 66SL, 1.2 qt Manex 4F, 1.6 qt 823.50 d

2005 research trial Treatment, rate/a Non-treated lb./a 1,873.2 c Manex 4F, 1.6 qt 3,056.9 ab Reason 500SC, 5.5 fl oz Manex 4F, 1.6 qt 2,634.2 bc Pristine 38WG, 18.5 oz Manex 4F, 1.6 qt 3,461.1 a Amistar 80WP 5 oz Manex 4F, 1.6 qt 3,414.5 a Tanos 50WDG, 8 oz + Manex 4F, 1.6 qt Curzate 60DF, 3.2 oz 2,958.1 ab Curzate 60DF, 3.2 oz + Manex 4F, 1.6 qt 2,814.2 ab Curzate 60DF, 5 oz + Manex 4F, 1.6 qt 3,171.0 ab Previcur Flex 66SL, 1.2 qt Manex 4F, 1.6 qt 3,138.6 ab

Downy Mildew by the Numbers 6 hours Time required for sporangial production- 100% RH 1 hour Time required for sporangia germination- free moisture & 68F 59-68F Optimum temp. for production of sporangia 4 days 1 generation-59 F nights & 77F days

Downy mildew trial methods 44 replication Randomized Applications aprox.. weekly 3-pont hitch application Pie pumpkin Applications 18 Jul-8 8 Sep

Treatment, rate/a Non-treated 2006 research trial AUDPC 1,242 a Cabrio 20EG, 12 oz Bravo WS, 2 pt 779 cd Bravo WS, 2 pt 718 cde Sonata, 2 qt + Previcure Flex 66F, 1.2 pt + Manex 4F, 1.6 qt 712 cde Ridomil Gold MZ 68WP, 2.5 lb Quadris Opti,, 3.2 pt 632 de Tanos 50WDG, 8 oz + Bravo WS, 2 pt Bravo WS, 2 pt + Curzate 60DF, 3.2 oz Ranman 400SC, 2.1 oz Bravo WS, 1.5 pt Ranman 400SC, 2.75 oz Bravo WS, 1.5 pt Previcur Flex 66 F Bravo WS, 2 pt 597 de 597 de 490 e 472 e

Systemic fungicides-group group 33 Fungicides Resistance Risk (FRAC) Alternation or tank mix Other diseases Aliette (fosetyl( fosetyl-al) Agri-Fos Fos, Phostrol, Prophyte (phosphorous acid, phosphite) 33-low. Some formulations recommend tank-mix. Some formulations list Phytophthora sp. and gummy stem blight

Fungicides for downy mildew management- Systemic fungicides-phosphonates (33) Some formulations labeled for additional diseases Tank mix recommended Resistance chance low

Cultural Management of Pumpkin Diseases Disease Bacterial fruit spot Black rot Downy mildew Fusarium fruit rot Powdery mildew Virus diseases Survival Residue Residue South Soil Residue & south South/weeds Comments Tillage/rotation critical Tillage/rotation critical Tillage/rotation not a factor At least 4 years rotation Tillage/rotation moderate importance Tillage/rotation not a factor