Kate Everts, Vegetable Pathologist, University of Delaware and University of Maryland; keverts@umd.edu
I frequently am asked for a “good” spray program for pumpkins. This is always a difficult program to design because it depends on field history (i.e. has Phytophthora crown rot occurred in the field), production practices (no-till vs. bare ground), and the grower’s philosophy about control (Cadillac treatment program vs. minimal inputs). Keep the following in mind to design a good spray program:
● Know what diseases are the most common on your farm. Previous problems with black rot, Phytophthora blight, anthracnose, scab or other diseases may indicate that these diseases are likely to be problems again.
● Know if downy mildew is present on Delmarva. When downy mildew is present your spray program should include effective downy mildew materials. Downy mildew was confirmed in Wicomico County, MD Aug. 17, 2010 (see below).
● Scout 50 old leaves in your field for powdery mildew lesions. If powdery mildew is present in the field, apply materials that are targeted for it.
● Even after implementing a program, scout your fields frequently and modify your program if new disease problems occur.
● Familiarize yourself with the Commercial Vegetable Production Recommendations section on pumpkins. Many fungicides are available for controlling different diseases.
Quintec is a newly registered powdery mildew fungicide. It has performed very well in my trials. Apply at 6 fl. oz. /A with chlorothalonil and alternate with other powdery mildew materials.
Downy mildew has been confirmed in Wicomico County, Maryland. Fungicide spray programs should be revised to include fungicides with good efficacy on downy mildew.
Sprays should be applied on a 7-day schedule. The most effective materials are Ranman, Presidio and Previcur Flex. Tank-mix with a protectant such as chlorothalonil–1.5-3 pt 6F/A and alternate between different modes of action (FRAC codes):
Ranman–2.1-2.75 fl. oz 400 SC/A, plus an adjuvant
or
Presidio–3.0-4.0 fl oz 4SC/A
or
Previcur Flex–1.2 pt 6F/A
Other materials for use in tank mix or alternation:
Tanos–8.0 oz 50WDG/A
or
Curzate–3.2 oz 60DF/A
Materials with different modes of action (FRAC codes) should always be alternated to reduce the chances for fungicide resistance development.
A good fungicide spray program will increase yields and improve quality. The single best way to improve handle quality is to control foliar and fruit diseases in season.