Commercial Disease Controls
The Pennsylvania State University
Cooperative Extension
Cucumbers
Seed Treatment
Check with seedsman to determine if seed has been treated with an insecticide and fungicide. If it has not been treated, use a mixture of thiram 75WP (1/2 teaspoon per pound or 3 ounces per 100 pounds) and an approved commercially available insecticide.
Disease Control
Damping-Off
Apply the following in a 7-inch band after seeding. Use formula given in the "Calibration for Changing from Broadcast to Band Application" section of Calibrating Granular Application Equipment to determine amount of Ridomil Gold or Ultra Flourish needed per acre.
mefenoxam--l-2 pt Ridomil Gold 4E/A or 2-4 pt Ultra Flourish 2E/A
Viruses (CMV, WMV, PRSV, ZYMV)
Use resistant varieties where possible.
Plant fields as far away from existing cucurbit plantings as possible to prevent aphid transmission of viruses from existing fields to new fields.
Bacterial Wilt
Insect control is essential for prevention of wilt. Control cucumber beetles before they feed on plants.
Angular Leaf Spot
At first sign of disease, apply the labeled rate of fixed copper plus mancozeb (1 pound active ingredient per acre). Repeat every 7 days. To minimize the spread of disease, avoid working in field while foliage is wet.
Powdery Mildew
The fungus that causes powdery mildew has developed resistance to several classes of fungicides. The fungicides at risk for resistance development such as Strains of the pathogen that are highly resistant to some strobilurins/Class 11/QoI fungicides (Cabrio, Flint, Amistar, Quadris and Tanos) have been reported in the Eastern U.S. in 2004 and 2005.
Powdery Mildew generally occurs from mid-July until the end of the season. Excellent resistance is available in all recommended cucumber varieties. Observe fields for the presence of powdery mildew. If one lesion is found on the underside of 45 old leaves, begin the following fungicide program:
Alternate:
Chlorothalonil (Bravo, Echo, Equus)--2-3pt 6F/A or OLF plus Nova--5oz 40W/A, or
Chlorothalonil (Bravo, Echo, Equus)--2-3pt 6F/A or OLF plus Procure--4-8 oz 50WS/A,
with a tank mix containing chlorothalonil and
Pristine--12.5-18.5 oz 38WG/A
Downy Mildew
Cultivars that were resistant in the past may no longer be resistant because of possible recent shifts on the pathogen population. The disease generally does not occur until mid-August, however, scout fields for disease incidence beginning in mid-July. Refer to the Cucurbit Downy Mildew Forecasting website (http://www.ces.ncsu.edu/depts/pp/cucurbit/) for current status of the disease. Begin sprays when vines run, or if disease occurrence is predicted for the region. Preventative applications are much more effective than applications made after disease is detected. Resistance to the QoI/Class II fungicides has been reported in the Eastern U.S. The following are the most effective materials (tank mix these products with a protectant such as chlorothalonil (Bravo, Echo, Equus)--1.5 pt 6F/A or OLF):
Ranman--2.1-2.75 fl oz 400SC/A or
Previcur Flex--1.2pt 6F/A or
Gavel--1.5-2 lb75DF/A (Gavel contains mancozeb, which is a protectant, and does not need a tank mix partner.)
Curzate--3.2 oz 60DF/A or
Pristine--12.5-18.5 oz 38WG/A, or
Tanos--8 oz 50 WDG/A or
Cabrio--8-12 oz. 20WG/A
Materials with different modes of action (FRAC group) should be alternated.
Sprays should be applied on a 7-day schedule. Cabrio, Pristine and Tanos should not be alternated with each other or used consecutively. Under severe disease conditions spray interval may be reduced if label allows.
Anthracnose
Excellent resistance is available in some varieties. Use resistant varieties whenever possible. Begin fungicide applications when vines run, or earlier if symptoms are detected. Alternate chlorothalonil or mancozeb with Cabrio or Quadris every 7 days. This is especially important to delay the development of resistant strains of the pathogen to Cabrio or Quadris.
Alternate:
chlorothalonil (Bravo, Echo, Equus)--l.5-3 pt 6F/A or OLF (use low rate early in season), or
mancozeb(Dithane, Manex II, Manzate, Penncozeb)-- 1.5-3 lb 75DF/A or OLF,
with
a tank mixture containing chlorothalonil or mancozeb and
azoxystrobin (Quadris--6.2 - 15.4 oz 2.08F/A or Amistar--2-5 oz 80WDG/A, or
Cabrio--12-16 oz 20EG/A, or
Pristine--18.5 oz 38WG/A
To improve the performance of chlorothalonil, combine it with:
Topsin M--0.5 lb 7OWP/A or OLF
Gummy Stem Blight
Occurs primarily in late summer. Fungicides at risk for resistance development such as strobilurins/Class 11/QoI fungicides (Cabrio, Flint, Amistar, and Quadris ) should be tank-mixed with a different class of fungicide to delay onset of resistance. When tank-mixing use at least the minimum labeled rate of each fungicide in the tank mix. Alternate with a non-QoI fungicide effective against gummy stem blight. Do not apply a QoI fungicide more than 4 times per season. If resistance to QoI fungicides exists in the area, do not use QoI fungicides. Use a fungicide from a different fungicide class.
Alternate:
chlorothalonil (Bravo, Echo, Equus)--2 pt 6F/A, or
mancozeb (Dithane, Manex II, Manzate, Penncozeb)--2-3 lb 8OWP/A
with a tank mixture containing chlorothalonil or mancozeb and
azoxystrobin (Quadris--6.2 - 15.4 oz 2.08F/A or Amistar--2-5 oz 80WDG/A, or
Cabrio--12-16 oz 20EG/A, or
Pristine--18.5 oz 38WG/A
Belly Rot
Apply the following at the 1- to 3-leaf stage. Make a second application just prior to vine tip over or 10 to 14 days later whichever comes first.
azoxystrobin (Quadris--6.2 - 15.4 oz 2.08F/A or Amistar--2-5 oz 80WDG/A
Scab
Disease occurs during cool periods. Excellent resistance is available in some varieties. Use resistant varieties when possible. Begin sprays as true leaves form. Repeat every 5 to 7 days.
chlorothalonil (Bravo, Echo, Equus)--2-3 pt 6F/A or OLF
Cottony Leak (Pythium)
At planting apply:
mefenoxain--l-2 pt Ridomil Gold 4E/A or 2-4 pt Ultra Flourish 2E/A. Apply in a 7-inch band after seeding. Use formula in the "Calibration for Changing from Broadcast to Band Application" Section of Calibrating Granular Application Equipment to determine the amount of Ridomil Gold or Ultra Flourish needed per acre.
Phytophthora Fruit Rot
To minimize the occurrence of this disease, rotate away from susceptible crops (Cucurbits, Peppers, Eggplants, and Tomatoes) for as many years as possible. Fields should be adequately drained to ensure that soil water does not accumulate around plants. Apply the following when conditions are favorable for disease development and always tank mix with another fungicide registered on cucumbers.
Forum--6 oz 4.18SC/A, (must be tank mixed with another fungicide active against Phytophthora blight on pumpkins and winter squash such as fixed copper), or
Gavel--1.5-2 lb75DF/A, or
Tanos--8 oz 50 WDG/A (suppression only), or
Ranman--2.75 fl oz 400SC/A
Note: Where trade names are used, no discrimination is intended
and no endorsement by the Cooperative Extension Service is implied.
Information provided is intended for consideration by the user, but is not
intended to be a recommendation. Production decisions should be based on
consideration of many types of information (scientific, experiential, economic,
legal, etc.) available to the user.
