Posts Tagged ‘pumpkin’

Cucurbit Downy Mildew Alert!

Friday, June 15th, 2012

Kate Everts, Vegetable Pathologist, University of Delaware and University of Maryland;

Cucurbit downy mildew was confirmed in Dorchester and Caroline counties in Maryland on June 12. Symptoms first appeared on June 8. This downy mildew occurrence is one month earlier than any occurrence in recent years. Growers should scout aggressively for this disease on cucumber and other cucurbits. This disease is favored by cool, humid weather including cool dewy nights. Weather during June 12-14 is forecast to be conducive to further spread. Tank-mix Ranman or Previcur Flex with a protectant fungicide and alternate sprays with a material with a different mode of action. Be careful not to rely on one fungicide class. Use excellent resistance management practices to avoid allowing the pathogen to develop resistance and to improve the efficacy of your fungicide management program. Presidio, which was commonly used in previous years, was not as effective as expected in 2011 University trials.

Downy mildew on the lower surface of a cucumber leaf. Notice the angular, water soaked lesions on this newly infected leaf. (Image courtesy of Bugwood and Gerald Holmes)

Consult the Commercial Vegetable Production Recommendations for further information on resistance management and available fungicides (in Maryland, Extension Bulletin 236 and in Delaware, Extension Bulletin 137). Because downy mildew has only been found on cucumber, targeted sprays on other cucurbits crops such as pumpkin, squash, watermelon, etc. are not necessary, at this time. Instead scout these crops aggressively and continue to apply a broad-spectrum spray program.

Watch for Striped Cucumber Beetle and Squash Bugs at Base of Cucurbit Plants

Friday, June 8th, 2012

Jerry Brust, IPM Vegetable Specialist, University of Maryland;

I talk about this every year it seems, but I still see cucumber beetle and squash bug problems at the base of growers’ cucurbit plants. So far this has been a ‘good’ year for striped cucumber beetle and squash bug populations in just about every cucurbit field. Some fields have been hit particularly hard with beetles causing 5-10% plant loss due just to their feeding. The biggest problem with these pests, and why control sprays have not worked well, is that they are consistently hiding at the base of the plant where they are feeding on the stem. Most of the time we look for the foliage damage to tell us how well our spray program is working. Sprayers are set up usually to cover a lot of leaf canopy and do not do a very good job of putting chemical along the base of the stem. This stem feeding can be severe enough on small plants that either pest alone could cause some wilting, but with both feeding on this relatively small area of the stem they are causing considerable damage (Fig. 1). Even on larger plants the feeding can still cause significant damage (Fig. 2). It is hard enough to kill squash bug adults with a good cover spray, but when only small amounts of spray are reaching them on the lower stem they will not be controlled. Often it is possible to walk by plants and even inspect them and still see no beetles or squash bugs, as they will stay down at the base of the plant and only move when the base is exposed. In a couple fields about 10% of the plants were wilting (Fig. 3) due to squash bug and cucumber beetle feeding. These pictures are from a squash field but the same problem is occurring in watermelon and cantaloupe fields with both striped cucumber beetles and squash bugs feeding at the base of a plant. Growers need to check to see if this type of feeding is occurring in their fields and if so insecticide applications (pyrethroids such as Asana, Warrior, etc.) must be directed at the base of the plant.

Figure 1. Striped cucumber beetle feeding damage at base of a small squash plant


Figure 2. Larger cucurbit plant with feeding at its base by cucumber beetle

Figure 3. Wilted squash plant due to squash bug and cucumber beetle feeding at its base

Cucurbit Downy Mildew Fungicide Decisions

Friday, May 11th, 2012

Kate Everts, Vegetable Pathologist, University of Delaware and University of Maryland;

Downy mildew on cucurbits has been a problem on Delmarva beginning in early July for the last few years. Good fungicides for management are available. However, last year in my trials, one of these fungicides, Presidio, was not as effective as expected. Looking ahead to your spray program, be careful not to rely on one fungicide class. It is difficult to know which fungicides will be effective here, because our population does not overwinter and is reintroduced from the South each year. Therefore use excellent resistance management practices to avoid allowing the pathogen to develop resistance and to improve the efficacy of your fungicide management program.

Fungicide Resistance management guidelines by crop are available online and hard copies are available in Delaware at the county Extension offices.

Vegetable Disease Update – September 16, 2011

Friday, September 16th, 2011

Bob Mulrooney, Extension Plant Pathologist;

Lima bean downy mildew was found by a CCA and confirmed on Wednesday from a field of ‘C-elite’ near Galena, MD. Growers need to be scouting carefully and applying fungicides as needed. If seen in the field apply either Ridomil Gold/Copper 2.0 lbs/A or ProPhyt (3.0 pts/A). See the 2011 Delaware Commercial Vegetable Production Recommendations for other fungicide choices as well as last week’s WCU for more detailed information.

Basil downy mildew was found in New Castle County this week. Any specialty crops growers might want to protect basil with one of the phosphorus acid products, such a ProPhyt, at this time.

Powdery and downy mildew are widespread in cucurbits especially pumpkins and winter squash at this time. Maintain fungicide programs until fruit develop fully.

Unfortunately Phytophthora fruit rot is very prevalent on a number of cucurbits especially pumpkin at this time. The excessive rainfall just made a bad problem worse. A few growers have asked about dipping fruit in a 5-10% bleach solution or using Zerotol to prevent fruit rot. My experience has been that is not effective if the fruit are infected in the field. You may get reduced spread in a bin but it will not control Phytophthora fruit rot.

There were a few reports of late blight in New York and Connecticut this week, but nothing in the Mid-Atlantic to worry tomato growers so far. To track the progress of late blight in the US you can go to

Vegetable Disease Update – August 26, 2011

Friday, August 26th, 2011

Bob Mulrooney, Extension Plant Pathologist;

With the impending hurricane we will probably see large amounts of rainfall. For vine crops fields with a history of Phytophthora fruit rot it will mean more Phytophthora fruit rot if any marketable watermelon or cantaloupe remain but it will really threaten the pumpkin crop. No fungicide will protect fruit from fruit rot if we get huge amounts of rainfall. Standing water in the fields will be the biggest indicator of possible fruit rot damage. There would be some benefit to protecting foliage with fungicides before the storm arrives if there is time and there is no history of Phytophthora fruit rot. This would be true for many vegetables including vine crops, tomatoes, and others. If there is no Phytophthora fruit rot present in a pumpkin field, fungicides such as Presidio, Ranman, Revus or Forum plus a fixed copper could be considered to suppress Phytophthora fruit rot, if Phytophthora spores moving in water from other fields should be introduced. Fruit have to be covered for the materials to have a hope of having an effect.

For other vegetables such as tomatoes, peppers and other fruiting vegetables that may be planted for late harvest fungicide applications should be made before the rains arrive not after. Prevention is the key to control. If the label allows, adjuvants that help products adhere to the plants should be considered. Spreader-stickers would be encouraged if the crop and label warrant it.

In crops where cottony leak caused by Pythium could cause crop loss, such as snapbeans and lima beans, application of one of the phosphonate fungicides such as ProPhyt or Phostrol would be suggested at maximum rates, or Ridomil Gold/Copper on snapbeans only. There is a 24c label for Ridomil Gold/Copper (2.0 lbs/A) in DE, MD and VA for cottony leak on snapbeans. Lima bean growers will want to scout carefully once this storm clears out for downy mildew. Wet soil and cool temperatures will favor downy mildew infection.

Cucurbit downy mildew is present on pumpkin now in the sentinel plot in Newark in New Castle County. This is the first report of downy mildew on pumpkin. It has probably been there for several days. Growers should continue to apply fungicides for leaf diseases including downy mildew.


Cucurbit Downy Mildew Update – August 19, 2011

Friday, August 19th, 2011

Bob Mulrooney, Extension Plant Pathologist;

There were reports of downy mildew on pumpkin in northern New Jersey at the beginning of the week. This was sent to the WCU mailing list to make you aware that downy mildew was beginning to appear on more than just pickling cucumber in the area. With the recent thunderstorms, cooler nights and morning fog, conditions will be more favorable for disease development. Maintain your fungicide program at this time. Growers should be aware that the fungicides that have been the most effective on downy mildew on cucumber (namely Presidio, Ranman, and Previcur Flex) will also be very effective on pumpkin, cantaloupe and any other cucurbit. Tanos and Curzate could be added to that list as well for cucurbits other than cucumber. Be aware that Presidio has some plant back restrictions for crops not on the label. The link will take you the new supplemental label: Wheat can be planted 30 days after treatment. This was added in the supplemental label.

Gavel 75DF from Gowan Company LLC Now Labeled for Pumpkin and Winter Squash

Thursday, August 4th, 2011

Bob Mulrooney, Extension Plant Pathologist;

Gavel has been labeled for use on pumpkin and winter squash for the control of Alternaria leaf spot, Cercospora leaf spot, downy mildew and Phytophthora fruit and stem rot. This is in addition to labels for use on cucumber, cantaloupe, summer squash and watermelon. Gavel is not recommended for downy mildew control on cucumbers but is recommended for control on pumpkin and winter squash as well as watermelon and cantaloupe. Remember that Gavel contains mancozeb, so some cantaloupe varieties might be sensitive. Go to to see updated label.

Controlling Powdery Mildew in Cucurbits

Friday, July 8th, 2011

Kate Everts, Vegetable Pathologist, University of Delaware and University of Maryland;

Powdery mildew is a problem on cucurbits each year. All cucurbits are susceptible, however host plant resistance in many cucumber and cantaloupe cultivars has successfully managed the problem. Susceptible varieties as well as other crops like pumpkin and squash are hit hard by powdery mildew. Disease builds up during July and becomes severe in August and September. Powdery mildew is a challenge to manage, especially in hot dry conditions. Also, there is resistance in the powdery mildew pathogen to many of our fungicides such as Quadris. Therefore, fungicides must be chosen carefully.

To manage powdery mildew, select cultivars (varieties) with resistance or tolerance. Even a moderate level of resistance will improve the efficacy of a fungicide spray (and help reduce the damage if you miss a spray). Scout the field and apply the first powdery mildew spray when you see one lesion on the underside of 45 old leaves.

Always follow good resistance management guidelines. 1) Keep on a good spray schedule (a 7-day interval for powdery mildew). 2) Apply fungicides at label rate (don’t cut the rate). 3) Be sure you are getting good fungicide coverage of your plants. 4) Be aware of products that are at risk for resistance development. 5) Materials with different modes of action (FRAC codes) should always be alternated. 6) Late in the season when powdery mildew has become well established, only apply protectant fungicides such as chlorothalonil or sulfur.

Below are the fungicide programs suggested for the various crops.

Summer Squash or Cucumber: Alternate a tank mix that contains chlorothalonil and either Procure, Rally, Folicur, or Inspire Super, with a tank mix containing Pristine plus chlorothalonil.

Muskmelon: Alternate Quintec plus chlorothalonil, with a tank mix containing chlorothalonil and either Procure, Rally, Folicur, or Inspire Super.

Extensive white sporulation of powdery mildew on pumpkin leaves.

Pumpkin: Alternate Quintec plus chlorothalonil with a tank mix containing chlorothalonil and either Pristine, Procure, Rally, Folicur, or Inspire Super. An alternative and less expensive option is to alternate Micronized Wettable Sulfur with one of the above options. Sulfur may injure plants, especially at high temperatures, which is why it is only recommended for pumpkin. Certain varieties can be more sensitive.


Cucurbit Downy Mildew Alert – July 1, 2011

Friday, July 1st, 2011

Bob Mulrooney, Extension Plant Pathologist; and Kate Everts, Vegetable Pathologist, University of Delaware and University of Maryland;

Downy mildew was confirmed on seeded cucumbers in Cumberland County, NJ near the city of Vineland. There were no reported downy mildew infections on any transplanted cucurbits in this area. This is the first report of downy mildew on cucurbits in the Mid-Atlantic region this year. Downy mildew has also been increasing in North Carolina the last several weeks. This is a very long leap from NC to NJ if this infection was from air transported spores. Traditionally we can expect downy mildew to arrive here sometime around the 4th of July. DE and MD have sentinel plots for monitoring downy mildew on cucurbits and have been negative for downy so far. These are scouted regularly in addition to reports and samples that we receive from the field. Hopefully we can provide an early warning when it appears here so that timely fungicide applications with downy mildew specific fungicides can be made.

What growers should do:

● Now that downy mildew has been detected in the region growers should be scouting on a daily basis.

● In areas where rainfall has occurred, growers may want to apply targeted fungicides to cucumbers. Tank- mix Presidio, Ranman, or Previcur Flex with a protectant fungicide and alternate sprays with a material with a different mode of action. Because downy mildew has only been found in adjacent states on cucumber, targeted sprays on other cucurbits crops (pumpkin, squash, watermelon, etc.) are not necessary, at this time. Instead scout aggressively and continue a broad-spectrum spray program.

● All abandoned cucumber and summer squash fields should be sprayed with gramoxone or disced under immediately after last harvest to kill the foliage! Abandoned fields left unattended after use will only serve as a source of inoculum for other fields once downy mildew makes its way into our area.

● Please see the 2011 Commercial Vegetable Recommendations Guide for specific fungicide recommendations

● To track the progress of cucurbit downy mildew in the eastern US and to keep up with reports of Downy mildew from other states please visit North Carolina State University’s Cucurbit Downy Mildew Forecasting Center at


Phytophthora Fruit Rot on Cucurbits

Friday, June 24th, 2011

Bob Mulrooney, Extension Plant Pathologist;

Conditions have not been very favorable for fruit rot lately but we always seem to run the risk of scattered thunderstorms and frog-strangling rain events at this time of the year. Phytophthora blight is a tough disease to control, but if you have cucurbits in fields that had fruit rot in the past you are at very high risk if the soil stays saturated even for a few hours. This is a fungus that moves in water and the spores will move where water goes. (Spores will not move more than a few feet in the air.) Some additional cultural controls would be rotation (5 years or more) for watermelons, sub-soiling between the rows before they close to help water drain faster and to keep the fruit out of standing water. Fungicides will only suppress the disease and those that have the best activity are the following: Presidio, Revus, Ranman plus a surfactant (see label), Forum, Gavel and Tanos. Depending on the test, the season, and the location, the efficacy of these fungicides varies. However, proper application of these products will result in better yields than in untreated fields. Remember that Revus and Forum are Group 40 fungicides and have the same mode of action, so they should not be applied in succession. All of these fungicides except Ranman should be tank mixed with fixed copper if the label allows. Fixed copper is not compatible with Ranman plus the surfactant. Good coverage of fruit is very important. For more information on fungicides check the 2011 Commercial Vegetable Production Recommendations.