Posts Tagged ‘winter squash’

Results of the 2010 On-Farm Cucurbit Powdery Mildew Fungicide Resistance Trial

Friday, June 10th, 2011

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

In 2010 a multi-state project including DE, PA, MD, VA, NY and NJ was undertaken to determine the extent of resistance to fungicides for powdery mildew control in cucurbits. Plants of a susceptible pumpkin variety were grown to the 2-3 leaf stage, sprayed with different fungicides at varying rates and placed in commercial cucurbit fields with powdery mildew for 1-2 days. The plants were collected and allowed to continue to grow and develop symptoms in a greenhouse, then evaluated for the amount of powdery mildew on the leaves compared to the untreated plants exposed at the same time. The results from the two fields in DE showed that at least for these two fields that there is resistance in the powdery mildew populations to Topsin M, Flint, Endura, and Rally. The resistance to Rally at the high rate was very low indicating that some control would be expected at the highest label rate of Rally. No resistance was detected to Quintec, either in DE or any other state. I did not include Inspire or Folicur. No resistance was found to Inspire, but NY and PA did see some resistance to tebuconazole (Folicur). Cucurbit growers in DE and MD should not expect to see control of powdery mildew from thiophanate-methyl (TopsinM), or a stand-alone strobilurin fungicide like Flint, Quadris or Cabrio. The results of this trial indicate that the high rate of Pristine (Endura plus Cabrio) may still provide some control but there is resistance to the boscalid (Endura) component occurring in the region.

 

Cucurbit Downy Mildew Update – August 20, 2010

Friday, August 20th, 2010

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

The forecast for downy continues to be moderate to low for most of Delaware and the eastern shore. Maintain fungicide programs to protect cucurbits from infection by downy mildew. This time of year it begins to move to pumpkin, winter and summer squash, cantaloupe and watermelon. For more information on the forecast see the website http://cdm.ipmpipe.org.

Pumpkins, Winter Squash and Gourds Added to Quintec Label

Friday, August 13th, 2010

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

Several additional cucurbit crops were added to the Quintec label and the changes are not in the 2010 Vegetable Recommendations book. Quintec is labeled for powdery mildew control on winter squash, gourds and pumpkin in addition to watermelon, cantaloupe and other melons such as honeydew and others. Rates range from 4-6 fl oz/A. See label for details. This is a good powdery mildew fungicide and should be used in rotation with other fungicides for powdery mildew. Be sure to read the label to avoid fungicide resistance.

Cucurbit Downy Mildew Update – July 16, 2010

Friday, July 16th, 2010

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

Wednesday’s rain was a high risk event for cucurbit downy mildew in the region. Be sure downy mildew fungicides are being employed for disease control at this time. There have been no new reports of downy mildew in DE, MD, NJ or PA. That will probably change if this weather pattern continues. Keep current on disease progress by visiting http://cdm.ipmpipe.org/.

Vegetable Disease Update – July 2, 2010

Friday, July 2nd, 2010

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

Cucurbit Downy Mildew
We are at minimal risk at the present but keep up to date by checking the ipm PIPE website http://cdm.ipmpipe.org regularly for updates. Downy mildew was found in New York state for the first time on cucumber in Erie and Niagara counties close to the Ontario, Canada infection site. The northern march of downy has been slowed. We have had some weather patterns coming north but the clear skies and plenty of UV radiation have probably been keeping viable spore number low. We are checking our sentinel plots weekly for downy mildew here in DE.

Bacterial Wilt
Bacterial wilt on slicing cucumbers was diagnosed this week. Symptoms on this planting were random wilting of several runners on 20% of the plants. Sticky strands of bacterial ooze can be seen when the cut ends of the wilted runners are touched together then slowly drawn apart. Striped and spotted cucumber beetles carry the bacteria on their mouthparts and inoculate them when they feed on the succulent stems early in the season. Bacterial wilt is not seed borne and does not persist in the soil more than 2-3 months. It is thought that the bacteria acquire the bacteria from infected weed or volunteer cucurbit hosts. Cucumber beetle control is the primary control method.

Strands of bacterial ooze from touching cut ends of infected runner and pulling them apart slowly

Potato and Tomato Late Blight Webinar for Home Gardeners
Rutgers, Penn State and Cornell University vegetable plant pathologists will be holding a Webinar on Potato and Tomato Late Blight for home gardeners on July 13, 2010 at 6:30 PM. You are encouraged to participate in this timely topic. The linked announcement has all the information to enroll. It will be a good review for commercial producers as well.

Pythium Blight or Cottony Leak on Snap Beans
Pythium blight or cottony leak on snap beans was diagnosed early this week. This disease likes the hot, humid conditions that we had before this recent break in the weather. When we go back to the humid weather again with scattered showers and irrigation this disease can be a threat. Look for the cottony white growth in the lower canopy and on pods close to the ground. There is a 24c registration for Ridomil Gold Copper (2 lbs/A) for prevention of Pythium blight in DE, MD and VA. Several applications may be necessary if favorable weather persists.

Cucurbit Powdery Mildew
Powdery mildew on cucurbits has been reported in New Jersey. Delaware growers should be scouting and begin applying fungicides for powdery mildew once 1 old leaf in 45 has been found with powdery mildew. See the article titled Powdery Mildew on Cucurbits in WCU 18:15 for suggested fungicides.

Powdery Mildew on Cucurbits

Friday, June 25th, 2010

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

Continue to scout cucurbits for powdery mildew. 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 one lesion is found on the underside of 45 leaves. For control of cucurbit powdery mildew in:

Pumpkin and Winter Squash:
Alternate:
Rally (myclobutanil, 3) at 5.0 oz 40WSP/A plus chlorothalonil at 2.0 to 3.0 pt 6F/A
or
Procure (triflumizole, 3) at 4.0 to 8.0 oz 50WS/A plus chlorothalonil at 2.0 to 3.0 pt 6F/A
or
Folicur (tebuconazole, 3) at 4.0 to 6.0 fl. oz 3.6F/A plus chlorothalonil at 2.0 to 3.0 pt 6F/A

With one of the following:
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 to 18.5 oz 38WG/A
or
Quintec (quinoxyfen, 13) at 6.0 oz 2.08F/A plus chlorothalonil at 2.0 to 3.0 pt 6F/A

When 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:
Alternate:
Rally (myclobutanil, 3) at 5.0 oz 40WSP/A plus chlorothalonil at 2.0 to 3.0 pt 6F/A
or
Procure (triflumizole, 3) at 4.0 to 8.0 oz 50WS/A plus chlorothalonil at 2.0 to 3.0 pt 6F/A
or
Folicur (tebuconazole, 3) at 4.0 to 6.0 fl. oz 3.6F/A plus chlorothalonil at 2.0 to 3.0 pt 6F/A

With a tank mix containing:
chlorothalonil plus Pristine (pyraclostrobin + boscalid, 11 + 7) at 12.5 to 18.5 oz 38WG/A

Muskmelon and Watermelon:
Alternate:
Rally (myclobutanil, 3) at 5.0 oz 40WSP/A plus chlorothalonil at 2.0 to 3.0 pt 6F/A
or
Procure (triflumizole, 3) at 4.0 to 8.0 oz 50WS/A plus chlorothalonil at 2.0 to 3.0 pt 6F/A
or
Folicur (tebuconazole, 3) at 4.0 to 6.0 fl. oz 3.6F/A plus chlorothalonil at 2.0 to 3.0 pt 6F/A

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

For more information on control of powdery mildew of cucurbits please see the 2010 Delaware Commercial Vegetable Production Recommendations Guide.

Downy Mildew on Cucurbits – August 21, 2009

Friday, August 21st, 2009

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

The weather continues to be very favorable for downy mildew. It is spreading now to hosts other than cucumber. Cantaloupe, watermelon, winter squash and pumpkin have all been infected in the region. The spots are much smaller on butternut squash and watermelon but still produce the small tuft of fungus growth on the underside of the leaf. All cucurbit growers need to be including a fungicide specific for downy mildew in their spray rotation such as Previcur Flex, Ranman, Presidio, or Tanos at this time. Follow the label directions for plant-back restrictions, mixing partners, such as Bravo and mancozeb, and adjuvants. See the 2009 Commercial Vegetable Productions Recommendations for more information. Check the Cucurbit Downy Mildew ipmPIPE web site as well http://cdm.ipmpipe.org for more information.

cucurbit downy mildew symptoms on watermeloncucurbit downy mildew symptoms on watermelon

Downy mildew on the upper surface of watermelon leaves. Fungal growth on the underside of the leaves is often sparse.

Pumpkin Plants Turn Ugly in Just a Few Days

Friday, August 14th, 2009

Jerry Brust, IPM Vegetable Specialist, University of Maryland; jbrust@umd.edu

Last Thursday, August 6, my pumpkin plants looked great with large green leaves and just a little powdery mildew (Fig. 1). Just a few days later and they looked horrid (Fig. 2). Some leaves were just splotched with little yellow spots, while other leaves had necrotic edges (Fig. 3). By the calls I have been getting so far this week this same sort of thing is happening in many other pumpkin fields around Maryland. Exactly what could cause such a rapid decline of the foliage is still not clear. The weather over the weekend and for the last few days was some of the hottest and most humid we have had so far this summer. Pumpkins are sizing on the vine and the plants are under stress. In some of the fields the soil moisture seemed adequate, but greater levels are needed when it is this hot and plants and fruit are large. In most of the fields downy mildew was either established or just getting started. Whether it was the weather that weakened the plants and the downy mildew could take-off or the low level of infection of the downy mildew further stressed the plants when it was so hot and humid is unclear and does not really matter as the downy mildew needs to be controlled before it gets any worse. Best management practices for downy have been reported by Bob and Kate over the last few weeks. (Editor’s Note: See articles in WCU 17:17, WCU 17:18, and WCU 17:19 for fungicide recommendations from Bob Mulrooney and Kate Everts.)

Another factor may have been soil pH that was a little low but certainly tolerable, i.e., 5.7-6.0. These pH levels usually are not a problem but when the plant is under stress any additional stress will just add to the misery of that plant. At this point in time you cannot do anything about your pH, so be sure to reduce as many other stresses as you can—disease, insects (squash bug and cucumber beetles), and lack of water.

healthy pumpkin plantsFigure 1. Pumpkin field on Thursday, August 6, looking good

stressed pumpkin plantsFigure 2. Same pumpkin field on Wednesday, August 12, downy mildew is at low levels in the field

pumpkin leaf with downy mildew symptomsFigure 3. Pumpkin leaf with splotchy yellowing — downy mildew was found to be just starting on this leaf

Cucurbit Downy Mildew Update – August 14, 2009

Friday, August 14th, 2009

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

The weather continues to be very favorable for downy mildew. It is spreading now to hosts other than cucumber. Cantaloupe, watermelon, winter squash and pumpkin have all been infected in the region. The spots are much smaller on butternut squash and watermelon but still produce the small tuft of fungus growth on the underside of the leaf. All cucurbit growers need to be including a fungicide specific for downy mildew in their spray rotation such as Previcur Flex, Ranman, Presidio, or Tanos at this time. Follow the label directions for plant-back restrictions, mixing partners such as Bravo and mancozeb, and adjuvants. See the 2009 Commercial Vegetable Productions Recommendations for more information.

Cucurbit Downy Mildew Update – July 31, 2009

Friday, July 31st, 2009

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

Downy mildew continues to occur in commercial pickling cucumber fields. It is now widespread in all three counties in home gardens as well as on both slicing and pickling cucumber varieties. So far it has only been found on cucumbers. Conditions continue to be favorable for downy mildew on all our cucurbits. Be sure to be including downy mildew fungicides such as Ranman, Previcur Flex, Tanos and Presidio for downy mildew control. They all need to be tank mixed with a protectant fungicide. Disease pressure is increasing and waiting until the three leaf stage may not provide the control desired if infected plantings are nearby. Check the website often for the latest forecast at http://cdm.ipmpipe.org.