Cause Alternaria cucumerina is a fungus that overwinters on partly decayed melon plant refuse. It also may live in soil for short periods of time. The fungus is spread in infested soil or refuse, by wind and irrigation water, and also is transmitted by seed. Weak and senescent plants are more susceptible to infection.
Symptoms Leaf blight begins with small transparent spots enlarging to circular areas often involving most of the leaf. Spots darken with age and may show ridges, giving a target-like appearance. Defoliation may occur, exposing the fruit to sun scald. The fungus may cause melon decay in storage and transit. Small, brown, circular spots enlarge to 3-inches in diameter with definite sunken margins on the surface. Spots gradually turn black.
Cultural control
- Crop rotation.
- Turn under crop debris as soon as possible after harvest.
- Keep plants growing vigorously until harvest.
Chemical control Spray foliage and fruit when disease first appears. Apply all material in 100 to 150 gal water/A.
- Carboxamide (Group 7) formulations are registered for use. Do not make more than two (2) sequential applications before alternating to a labeled fungicide with a different mode of action.
- Endura at 6.5 oz/A on 7- to 14-day intervals. Preharvest interval is 0 days. 12-hr reentry.
- Fontelis at 12 to 16 fl oz/A on 7- to 14-day intervals. Preharvest interval is 1 day. 12-hr reentry.
- Chlorothalonil (Group M5) formulations are labeled.
- Bonide Fung-onil is available for home gardens. H
- Bravo Ultrex at 1.8 to 2.7 lb/A. 12-hr reentry.
- Echo 720 at 2 to 3 pints/A on 7-day intervals. Preharvest interval is 0 days. 12-hr reentry.
- Copper formulations (Group M1) offer limited control.
- Champ WG at 1.5 to 2 lb/A on 5- to 7-day intervals. 48-hr reentry. O
- Cueva at 0.5 to 2 gal/100 gal water on 7- to 10-day intervals. May be applied on the day of harvest. 4-hr reentry. O
- Cuprofix Ultra 40 Disperss at 1.25 to 2 lb/A on 5- to 7-day intervals. 48-hr reentry.
- Kocide 2000 at 1 to 2.25 lb/A or Kocide 3000 at 0.5 to 1.25 lb/A on 5- to 7-day intervals. 48-hr reentry. O
- Liqui-Cop at 2 to 3 teaspoons/gal water. H
- Previsto at 0.75 to 2 quarts/A on 5- to 7-day intervals. 48-hr reentry. O
- Mancozeb (Group M3) products such as Dithane F-45 at 1.6 to 2.4 quarts/A. Do not apply within 5 days of harvest. Several varieties are sensitive including Harvest Queen, Gold Star, Super Star, Sweet and Early, and Saticoy. 24-hr reentry.
- Mettle 125 ME (Group 3) at 8 fl oz/A on 7- to 10-day intervals. Application can be made the day of harvest. 12-hr reentry.
- Omega 500F at 0.75 to 1.5 pints/A on a 7- to 10-day intervals. Preharvest interval is 30 days. 12-hr reentry.
- OSO 500F 5% SC (Group 19) at 3.75 to 13 fl oz/A on 7- to 14-day intervals. Can be applied the day of harvest. 4-hr reentry. O
- Regalia (Group P5) at 1 to 4 quarts/A plus another fungicide on 7- to 10-day intervals. Does not benefit from the addition of an adjuvant. Preharvest interval is 0 days. 4-hr reentry. O
- Strobilurin fungicides (Group 11) are labeled for use. Do not make more than one (1) application of a Group 11 fungicide before alternating to a labeled fungicide with a different mode of action.
- Cabrio EG at 12 to 16 oz/A on 7- to 14-day intervals. Preharvest interval is 0 days. 12-hr reentry.
- Evito 480 SC at 3.0 to 5.7 fl oz/A on 7- to 14-day intervals. Preharvest interval is 1 day. 12-hr reentry.
- Quadris Flowable at 6 to 15.5 fl oz/A on 7- to 14-day intervals. Preharvest interval is 1 day. 4-hr reentry.
- Reason 500 SC at 5.5 fl oz/A on 5- to 10-day intervals. Do not apply within 14 days of harvest. 12-hr reentry.
- Trilogy at 0.5% to 1% Not labeled for use in Oregon. Do not use above 90°F or when plants are under heat or moisture stress. Do not use when foliage is wet as good coverage is essential. Poor control as a stand-alone product. 4-hr reentry. O
- Premixes of fungicides are available and offer ease for fungicide resistance management. Do not make more than one (1) application of a Group 11 fungicide before alternating to a labeled fungicide with a different mode of action; for other fungicide groups apply no more than two (2) sequential applications alternating with another fungicide with a different mode of action.
- Aprovia Top (Group 7 + 3) at 10.5 to 13.5 fl oz/A on 7- to 14-day intervals. May be applied the day of harvest. 12-hr reentry.
- Dexter Max (Group M3 + 11) at 2.1 to 3.2 lb/A on 7- to 10-day intervals. Some cantaloupe varieties are sensitive to Dexter Max. Preharvest interval is 5 days. 24-hr reentry.
- Dexter Xcel (Group M3 + 11 + 3) at 72 fl oz/A on 7- to 10-day intervals. Some cantaloupe varieties are sensitive to Dexter Xcel. Preharvest interval is 7 days. 24-hr reentry.
- Gavel 75 DF (Group 22 + M3) at 1.5 to 2.0 lb/A on 7- to 10-day intervals. Preharvest interval is 5 days. 48-hr reentry.
- Inspire Super (Group 3 + 9) at 16 to 20 fl oz/A on 7- to 10-day intervals. Preharvest interval is 7 days. 12-hr reentry.
- ManKocide (Group M1 + M3) at 2 to 3 lb/A on 7- to 10-day intervals. Under moderate to severe disease pressure use the higher rate on 5- to 7-day intervals. Do not apply within 5 days of harvest. 48-hr reentry.
- Merivon Xemium (Group 7 + 11) at 4 to 5.5 fl oz/A on 7- to 14-day intervals. Preharvest interval is 0 days. 12-hr reentry.
- Miravis Prime (Group 7 + 12) at 9.2 to 11.4 fl oz/A on 7- to 14-day intervals. Preharvest interval is 1 day. 12-hr reentry.
- Orondis Opti (Group M5 + 49) at 1.75 to 2.5 pints/A on 7- to 14-day intervals. May be applied the day of harvest. 12-hr reentry.
- Pristine (Group 7 + 11) at 12.5 to 18.5 oz/A on 7- to 14-day intervals. Preharvest interval is 0 days. 12-hr reentry.
- Quadris Opti (Group 11 + M5) at 3.2 pints/A or Quadris Top (Group 11 + 3) at 10 to 14 fl oz/A on 7- to 14-day intervals. Preharvest interval is 1 day. 12-hr reentry.
- Switch 62.5WG (Group 12 + 9) at 11 to 14 oz/A on 7- to 10-day intervals. Do not apply within 1 day of harvest. 12-hr reentry.