Kate Everts, Vegetable Pathologist, University of Maryland; keverts@umd.edu
A frequent question that I get from growers is “what is the best spray program for my pumpkin crop?”. It is a challenging question to answer, in part because each field/farm may have different disease pressure, and Ag Chem suppliers may only stock some fungicides. With that in mind, I have come up with the following step by step procedure to use as a guide in designing an individualized pumpkin program. The numbers in parenthesis that follow the fungicide name are the Fungicide Resistance Action Committee (FRAC) code for the product. Except for chlorothalonil, mancozeb and copper, always alternate fungicides with different FRAC codes.
Step 1
Use all available cultural practices to reduce disease pressure, including planting host resistant cultivars when possible, using good rotations, planting disease free seed, etc. If possible, modify your spray equipment to get excellent fungicide coverage on both the upper and lower surfaces of leaves.
Step 2
Learn to identify key diseases: powdery mildew, downy mildew, Plectosporium blight, and bacterial leaf spot.
Step 3
Begin a basic preventative spray program with a chlorothalonil or mancozeb product. Spray every 7 to 14 days, beginning when vines run. (Organic alternative: copper)
Step 4
Scout for disease presence and if the following diseases occur, use the following guidelines:
Bacterial leaf spot – Add a copper product to the basic preventative program (applied every 7 to 10 days).
Powdery mildew – Add powdery mildew specific products to basic preventative program. Alternate FRAC codes.
- Select one of these: Torino (U6), Vivando (U8), Luna Experience (3+7), or Quintec (13).
- And alternate with one of the following: Rally (3), tebuconazole (3), Procure (3), Proline (3), Inspire Super (3+9), Aprovia Top (3+11), TopGuard (3+11), or Pristine (7+11).
- (Organic alternative: Micronized Wettable Sulfer)
Downy mildew – Add downy mildew specific product to the basic preventative program. Select two downy mildew products with different FRAC codes and alternate them. Downy mildew products include: Orondis Ultra (U15+40), Orondis Opti (M5+U15), Ranman (21), Previcur Flex (28), Presidio (43), Elumin (22), Zing! ((M5+22), Ariston (M5+27), Tanos (11+27), Curzate (27), Forum (40), and Zampro (40+45).
Plectosporium blight – Chlorothalonil and mancozeb are good on Plectosporium blight. Cabrio can be added to the program to improve management.
Step 5
Special cases: Avoid planting pumpkins in a field with a history of Phytophthora fruit rot.
To manage Phytophthora fruit rot, select two of the following Phytophthora products that are in different FRAC code groups and rotate them. Phytophthora fruit products include Orondis Ultra (U15+40), Revus (40), Zampro (40+45), Presidio (43), Gavel (M3+22), Tanos (11+27), Ranman (21) and Forum (40).