Symptoms and Signs
In California, anthracnose is unusual on cucurbit crops other than seedless watermelon. It can cause leaf, fruit, and/or stem lesions. Foliage lesions are tan to brown except on watermelon foliage where they are dark brown to black. Fruit may develop brown to black, sunken, water-soaked spots. Tiny, black fruiting structures, called acervuli, form within the lesion. In wet weather, pink or orange spores ooze from these fruiting bodies.
Comments on the Disease
The fungus overwinters on cucurbit plant residue in the soil, on volunteer cucurbits, or on cucurbit seed. Disease development is favored by warm, wet weather. This disease is rarely seen in the field and more often occurs on transplants raised in the greenhouse.
Management
There is resistance in some varieties of watermelon and cucumber, but not in seedless watermelon. Control tactics include crop rotation, use of clean seed, and inspection of transplants. Avoid sprinkler irrigation and keep the tops of the beds dry. Fungicides are rarely needed in California but may be required on seedless watermelons at the first sign of disease.
| Common name | Amount per acre | REI‡ | PHI‡ | |
|---|---|---|---|---|
| (Example trade name) | (hours) | (days) | ||
| Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least likely to cause resistance are at the top of the table. When choosing a pesticide, consider information relating to the pesticide's properties and application timing, honey bees, and environmental impact. Always read the label of the product being used. | ||||
| A. | CHLOROTHALONIL | |||
| (Bravo Ultrex, etc.) | 1.4–1.8 lb | 12 | 0 | |
| MODE-OF-ACTION GROUP NAME (NUMBER1): Multi-site contact (M5) | ||||
| COMMENTS: Do not apply more than 19.1 lb/acre per season. | ||||
| B. | MANCOZEB | |||
| (Dithane DF) | 2–3 lb | 24 | 5 | |
| (Dithane F-45) | 1.6–2.4 qt | 24 | 5 | |
| (Dithane M-45) | 2–3 lb | 24 | 5 | |
| (Penncozeb 75DF) | Label rates | 24 | 5 | |
| MODE-OF-ACTION GROUP NAME (NUMBER1): Multi-site contact (M3) | ||||
| COMMENTS: Labeled for cucumbers, melons, watermelon, and summer squash only. | ||||
| ‡ | Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest. |
| 1 | Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of actions. Fungicides with a different group number are suitable to alternate in a resistance management program. In California, make no more than one application of fungicides with mode-of-action group numbers 1, 4, 9, 11, or 17 before rotating to a fungicide with a different mode-of-action group number; for fungicides with other group numbers, make no more than two consecutive applications before rotating to fungicide with a different mode-of-action group number. |