Posts Tagged ‘cucurbit powdery mildew’

Controlling Cucurbit Powdery Mildew

Friday, July 10th, 2009

Andy Wyenandt, Assistant Extension Specialist in Vegetable Pathology, Rutgers University; wyenandt@aesop.rutgers.edu 

Cucurbit powdery mildew(PM) season is just around the corner! Symptoms typically begin on older, lower leaves and can spread rapidly under dry, humid conditions.

Control of powdery mildew begins with regular scouting for symptoms and weekly fungicide applications. Begin a fungicide program when PM has been found in the region and/or when 1 lesion is found on the underside of 45 leaves. Fungicide resistance management of the fungus which causes powdery mildew is critical in the mid-Atlantic region! Fungicides with a high risk for resistance development, such as the strobilurin (Pristine, FRAC code 11) and Rally or Procure (FRAC code 3), should be tank mixed with a protectant fungicide such as chlorothalonil (M5) and rotated with fungicides of a different chemistry.

The following are some fungicide recommendations for control of powdery mildew in a variety of crops:

To control powdery mildew in pumpkin and winter squash:
Alternate:
Nova or Rally (myclobutanil, 3) at 5.0 oz 40WP/A plus chlorothalonil at 2.0-3.0 pt 6F/A
or
Procure (triflumizole, 3) at 4.0-8.0 oz 50WS/A plus chlorothalonil at 2.0-3.0 pt 6F/A

With:
Micronized Wettable Sulfur (M2) at 4.0 lb 80W/A; Sulfur may injure plants especially at high temperatures. Certain varieties can be more sensitive. Consult label for precautions.
or
chlorothalonil plus Pristine (pyraclostrobin + boscalid, 11 + 7) at 12.5-18.5 oz 38WG/A

If powdery mildew has become well established in the mid to late part of the season, only apply protectant fungicides such as chlorothalonil or sulfur.

To control powdery mildew in summer squash and cucumbers:
Alternate:
Nova or Rally (myclobutanil, 3) at 5.0 oz 40WP/A plus chlorothalonil at 2.0-3.0 pt 6F/A,
or
Procure (triflumizole, 3) at 4.0-8.0 oz 50WS/A plus chlorothalonil at 2.0-3.0 pt 6F/A

With:
chlorothalonil plus Pristine (pyraclostrobin + boscalid, 11 + 7) at 12.5-18.5 oz 38WG/A

To control powdery mildew in muskmelon and watermelon:
Alternate:
Nova or Rally (myclobutanil, 3) at 5.0 oz 40WP/A plus chlorothalonil at 2.0-3.0 pt 6F/A
or
Procure (triflumizole, 3) at 4.0-8.0 oz 50WS/A plus chlorothalonil at 2.0-3.0 pt 6F/A

With:
Quintec (quinoxyfen, 13) at 6.0 oz 2.08F/A plus chlorothalonil at 2.0-3.0 pt 6F/A
or
Pristine (pyraclostrobin + boscalid, 11 + 7) at 12.5-18.5 oz 38WG/A plus chlorothalonil at 2.0-3.0 pt 6F/A

For more information on control of powdery mildew of cucurbits please see the Delaware Commercial Vegetable Production Recommendations.

Cucurbit Downy Mildew Update

Friday, June 26th, 2009

Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu

Downy mildew was diagnosed on cucumbers in both Suffolk County and Northampton County on Delmarva this week. The Suffolk County find was in a small sentinel plot, and the Northampton find was a commercial cucumber field. The commercial field had been sprayed but the infected plants were up against a woods line and the aerial coverage might not have been sufficient to control the disease. If growers have the capability to make ground applications for downy mildew control it would be a good idea to get good coverage of any areas that might not have been covered by aerial applications. Again the recommended fungicides for downy mildew control on cucumbers are Previcur Flex, Ranman, Presidio and Tanos. All need a protectant tank mix partner. Ranman needs a surfactant such as Silwet. Be sure to read the labels for the details and rates. I do not recommend any Ridomil product because the fungus is resistant to that chemistry and Gavel and the phosphoric acid fungicides such as Prophyt and Phostrol are not effective on downy mildew on cucumbers. Fortunately the forecast for Thursday is low risk, be sure to check the forecast at the CDM ipmPIPE website http://cdm.ipmpipe.org for Friday and the weekend. It look like we will get a break in the weather for a short time but it will be important to keep a protectant fungicide on the crop at least.

New Resource for Cucurbit Growers
A laminated 8½ x 11 sheet of the FRAC Guidelines for Downy and Powdery Mildew on cucurbits is now available. These two diseases require frequent fungicide applications and both fungi have developed resistance to fungicides in the past. This quick reference should be helpful for those making fungicide choices in cucurbits, such as cucumbers, cantaloupes, watermelons, squash and pumpkins. These laminated sheets are available in the county offices or we can send you one. To print out your own copy check it out here http://www.rec.udel.edu/Update09/CucurbitDMPMfrac.pdf.

Pumpkins Ready for Harvest?

Thursday, August 28th, 2008

Andy Wyenandt, Assistant Extension Specialist in Vegetable Pathology, Rutgers University; wyenandt@aesop.rutgers.edu and Art Brown, Senior Associate Dean – Agriculture & Natural Resources, Rutgers University

The fall is almost upon us and because of the hot, dry summer many pumpkin fields will be ready for harvest much sooner than expected. For most roadside markets pumpkin season begins shortly after Labor Day and extends through the end of October. For those keeping track, that’s roughly an eight-week market. The question for many is what to do with marketable fruit in the field until it’s time for sale. As long as there is good, healthy foliage present, the best place for a pumpkin is on the vine. Foliage helps protect fruit from potential sunscald injury and will help any late setting fruit to size. However, keeping foliage around will also require additional fungicide applications. If the foliage cannot be maintained, move the mature fruit to a dry, well ventilated area. Many growers will let powdery mildew take the foliage out a few weeks before pumpkins are ready to be harvested. Why? Pumpkins are a lot easier to harvest without dense foliage in the field. Growers should be aware that the major drawback to this method is that powdery mildew can reduce stem quality by causing stems to turn brown and become brittle prematurely.

Once foliage is gone, pumpkins can easily be stored and ‘cured’ in the field by lopping them off the vine and placing them in un-stacked windrows as long as the weather cooperates. Temperatures of 80 – 85°F with relative humidity of 80 – 85% for 10 days after lopping are ideal. After this, temperatures between 50 – 60°F with 50 – 70% relative humidity will keep respiration and potential weight loss down. Cool, wet and ‘frosty’ weather will do most of the damage to ripe fruit in the field by slowing down the curing process, exposing fruit to potential fruit rot pathogens and, in the case of frosts, cause fruit to melt if temperatures get too low. Knowing your market, your crop and keeping an eye on the weather will go a long way in having a successful pumpkin harvest season.

Controlling Cucurbit Downy Mildew and Powdery Mildew

Friday, August 22nd, 2008

Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu

The recent high-pressure system that has brought us the dry weather and low humidity has slowed the progress of any downy mildew that is present. Spray schedules could be extended if the disease is not present or is at low levels. Cucurbits other than cucumbers are probably at low risk until we get some more humidity and dews in the morning. Usually this time of year we can have dew and fog until late morning, which is very favorable for downy mildew. Continue to check the downy mildew forecasting site at NC State for updates. http://www.ces.ncsu.edu/depts/pp/cucurbit/

Growers are having trouble with powdery mildew on pumpkins and other cucurbits at this time of year. This weather pattern has been very favorable for powdery mildew.

For Control of Cucurbit Powdery Mildew In:

Pumpkin and Winter Squash Fields
Alternate
Nova or Rally (myclobutanil, 3) at 5 oz 40WP/A plus chlorothalonil at 2-3 pt 6F/A
or
Procure (triflumizole, 3) at 4-8 oz 50WS/A plus chlorothalonil at 2-3 pt 6F/A
With
Micronized Wettable Sulfur (M2) at 4 lb 80W/A (Sulfur may injure plants especially at high temperatures. Certain varieties can be more sensitive. Consult label for precautions.)
or
Chlorothalonil plus Pristine (pyraclostrobin +boscalid, 11 + 7) at 12.5-18.5 oz 38WG/A

If powdery mildew has become well established in the mid to late part of the season, only apply protectant fungicides such as chlorothalonil or sulfur.

Summer Squash and Cucumber Fields
Alternate
Nova or Rally (myclobutanil, 3) at 5 oz 40WP/A plus chlorothalonil at 2-3 pt 6F/A
or
Procure (triflumizole, 3) at 4-8 oz 50WS/A plus chlorothalonil at 2-3 pt 6F/A
With
Chlorothalonil plus Pristine (pyraclostrobin + boscalid, 11 + 7) at 12.5-18.5 oz 38WG/A

Muskmelon and Watermelon Fields
Alternate
Nova or Rally (myclobutanil, 3) at 5 oz 40WP/A plus chlorothalonil at 2-3 pt 6F/A
or
Procure (triflumizole, 3) at 4-8 oz 50WS/A plus chlorothalonil at 2-3 pt 6F/A
With
Quintec (quinoxyfen, 13) at 6 oz 2.08F/A plus chlorothalonil at 2-3 pt 6F/A
or
Chlorothalonil plus Pristine (pyraclostrobin + boscalid, 11 + 7) at 12.5-18.5 oz 38WG/A

For more information on control of Powdery mildew of cucurbits please see the 2008 Delaware Commercial Vegetable Production Recommendations Guide.

Powdery Mildew on Watermelon

Thursday, August 21st, 2008

Kate Everts, Vegetable Pathologist, University of Delaware and University of Maryland; keverts@umd.edu

The cucurbit crops that are the most susceptible to powdery include pumpkin, squash, muskmelon, and cucumber that does not have resistance. However, in the past ten years, I have seen more and more watermelon fields where powdery mildew has become a problem. Quintec, a new fungicide that has excellent activity on powdery mildew, is registered on melons.

Remember that resistance to group 11 fungicides (strobilurin fungicides such as Quadris, Cabrio, or Flint) is widespread around the U.S. – do not rely on these materials. A good program for watermelon or muskmelon (cantaloupe) is to scout for powdery mildew and if it is present in the field, apply chlorothalonil plus Quintec rotated with Nova or Procure plus chlorothalonil. Quintec, a group 13 fungicide, has performed well in trials. Quintec has a 3 day PHI and is applied at 4 to 6 fl oz/A in 30 gallons of water (optimum spray volume). Aerial application is not allowed.

Cucurbit Diseases

Friday, August 8th, 2008

Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu

Conditions for downy mildew continue to be favorable, so preventative control for cucumber is important at this time. To date we have only observed downy mildew on cucumbers.

Powdery mildew is increasing on squash, cantaloupe and pumpkin, and has been seen on watermelon as well. It is often hard to see the infection on watermelon because the fungus sporulates sparsely on watermelon and the leaf color masks the fungus. Look for chlorotic spots on the upper surface of young, fully expanded leaves, and then inspect the corresponding lower leaf surface with a hand lens to confirm the presence of the fungus. On watermelon, if control is needed, alternate Nova /Bravo or Procure/Bravo with Quintec/Bravo or Pristine/Bravo. Any generic chlorothalonil can be substituted for Bravo.

Cucurbit Disease Update

Thursday, June 26th, 2008

Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu

Cucurbit Powdery Mildew
Powdery mildew has been found on zucchini in New Jersey.
Usually powdery mildew occurs from mid-July until the end of the season. Symptoms typically begin on older, lower leaves and can spread rapidly under dry, humid conditions. Control of powdery mildew begins with regular scouting for symptoms and weekly fungicide applications. Begin a fungicide program when PM has been found in the region and/or when 1 lesion is found on the underside of 45 leaves. Fungicide resistance management of the fungus which causes powdery mildew is critical in the mid-Atlantic region! Fungicides with a high risk for resistance development, such as the strobilurins (Pristine, FRAC code 11) and Nova or Procure (FRAC code 3), should be tank mixed with a protectant fungicide such as chlorothalonil (M5) and rotated with fungicides of a different chemistry.

For control of cucurbit powdery mildew in:

Pumpkin and winter squash fields:
Nova or Rally (myclobutanil, 3) at 5 oz 40WP/A plus chlorothalonil at 2-3 pt 6F/A,
or
Procure (triflumizole, 3) at 4-8 oz 50WS/A plus chlorothalonil at 2-3 pt 6F/A

Alternated with:

Micronized Wettable Sulfur (M2) at 4 lb 80W/A Sulfur may injure plants, especially at high temperatures. Certain varieties can be more sensitive. Consult label for precautions.
or
A tank mix containing chlorothalonil plus Pristine (pyraclostrobin + boscalid, 11 + 7) at 12.5-18.5 oz 38WG/A

If powdery mildew has become well established in the mid to late part of the season, only apply protectant fungicides such as chlorothalonil or sulfur.

Summer squash and cucumber fields:
Nova or Rally (myclobutanil, 3) at 5 oz 40WP/A plus chlorothalonil at 2-3 pt 6F/A,
or
Procure (triflumizole, 3) at 4-8 oz 50WS/A plus chlorothalonil at 2-3 pt 6F/A

Alternated with a tank mix containing:

Chlorothalonil plus Pristine (pyraclostrobin + boscalid, 11 + 7) at 12.5-18.5 oz 38WG/A

Muskmelon and watermelon fields:
Nova or Rally (myclobutanil, 3) at 5 oz 40WP/A plus chlorothalonil at 2-3 pt 6F/A,
or
Procure (triflumizole, 3) at 4-8 oz 50WS/A plus chlorothalonil at 2-3 pt 6F/A

Alternated with a tank mix containing:

Quintec (quinoxyfen, 13) at 6 oz 2.08F/A plus chlorothalonil at 2-3 pt 6F/A,
or
Chlorothalonil plus Pristine (pyraclostrobin + boscalid, 11 + 7) at 12.5-18.5 oz 38WG/A

For more information on control of powdery mildew of cucurbits please see the 2008 Delaware Commercial Vegetable Production Recommendations Guide.

Cucurbit Downy Mildew
Continue to check the website (http://www.ces.ncsu.edu/depts/pp/cucurbit/forecasts/c080625.php?month=06&year=08) for movement of downy mildew. The latest find in the South has been Reidsville, GA on butternut squash and slicing cucumber in a regional sentinel plot. There are reports of downy mildew from GA, SC and FL. The threat of movement north is very low as of June 26.