Posts Tagged ‘summer squash’

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.

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.

Transplant Shock

Thursday, May 13th, 2010

Gordon Johnson, Extension Fruit & Vegetable Specialist; gcjohn@udel.edu

The first seven days in May in 2010 saw temperatures in the high 80s and even some night temperatures in the low 70s in Delaware, and while windy, it was not excessively so. Then came the weekend of the 8th and 9th where average wind speeds doubled or tripled followed by low temperatures the middle of this week with scattered frost at night. These weather conditions illustrate the perils of setting out warm-season transplants in the beginning of May and to the need to take actions to avoid transplant shock.

Transplant shock will be evident by severe wilting, drying of leaves and stems, and, in severe cases, full plant collapse and death. This should not be confused with diseases such as Pythium damping off or damage from seed corn maggot or other soil insects.

Many of our transplants come from southern producers this time of year and there is always the potential for transplant shock when they are removed from southern greenhouses with little or no hardening and then are shipped up to Delaware in unheated trucks, especially when temperatures drop in the 40s or below during transport. Locally grown transplants are also susceptible to transplant shock if taken directly from greenhouses to the field without a hardening off process. Even with good hardening off, 40 mph winds can quickly desiccate plants if set in the field, especially without adequate windbreaks.

As a reminder, warm season vegetable transplants vary in their ability to withstand sub-optimal conditions depending on how well they have been hardened off and their inherent ability to withstand stress. Tomatoes, cucumbers, and squash are better able to handle early season stresses than cantaloupes, watermelons, or peppers.

Soil temperatures are a key factor in the establishment of warm season crops. It is important to lay plastic well ahead of planting and to have adequate soil moisture to absorb and then retain heat. When soil temperatures are too cold, root growth is minimal in these crops and root function is impaired. Water uptake is limited by low root activity and new growth and rooting-in is slowed. Root zone insects and diseases can further stress transplants and reduce stands in cold conditions.

To avoid transplant shock, make sure transplants have well developed root systems. Transplants should easily pull from trays and have full root balls. This is critical to avoid transplant shock. Do not rush transplants with poorly developed roots into the field. Make sure transplants have been hardened off well by exposing them to outside conditions, eliminating fertilizer, and controlling watering well ahead of planting. Leggy plants will be a problem in stressful conditions and should not be used if at all possible. Leggy plants are more susceptible to damage in transplanting and wind damage after planting thus subjecting them to additional stress.

It is important to plant so that soil covers the root ball and that the root ball is not exposed to drying. However, for crops such as watermelons and cantaloupes, make sure that soil does not surround the stem. Deep planting in cold wet soils will result in additional stress on melons. Extra care should be taken during transplanting during stressful periods to reduce injury to plants, particularly to root balls. Damage to roots will reduce establishment success especially in melons, cucumbers, and squash. Train planting crews so that they do minimal damage to transplants. If plants are not pulling well from trays and do not have intact root balls, plants will not survive adverse weather.

Avoid planting if weather conditions are unfavorable. Look at extended forecasts and plant on a warming trend where winds are not excessive. If heavy winds or very cold nights are expected, it is best to wait until more favorable weather returns. Often there is no earliness gained by planting in the stressful period; or gains are negated by stand losses and the need to replant areas. If weather conditions are unfavorable, you may also consider using row covers to protect plants.

Windbreaks are critical for early plantings. Use windbreaks between every bed for the early plantings and have windbreaks between multiple beds for later plantings. This year, many of our windbreaks offer minimal protection due to poor fall and winter growing conditions. Where windbreaks are not adequate, delay planting until favorable weather is in the forecast.

Wind Break Alternatives Planted in Late-Winter or Early-Spring for Spring Planted Vegetables

Wednesday, January 27th, 2010

January 25, 2010

Situation

Due to the wet fall in 2009, many vegetable growers on Delmarva were not able to plant small grain windbreaks such as winter rye in fields slated for watermelons, cantaloupes, and other vegetable crops in spring of 2010. 

Windbreaks most commonly are planted between groups of 3 or more beds to reduce wind damage and sandblasting on young crops.  Some growers have windbreaks between every bed to help trap heat and provide additional protection on early transplanted crops. Winter rye is the most common crop that is planted for windbreaks.  It is cold hardy, greens up early, and can reach a height of over 4 feet by late-April making it a good windbreak.   Winter wheat and barley have also been used but are later heading or are shorter.  Small grains are planted from late-September through early-November.  October plantings provide the best combination of tillering and winter cover without excessive fall growth.

In 2009, we had one of the wettest fall periods on record and many windbreaks were not planted.  Therefore, information on late winter or early spring planted alternatives is needed.  The following are questions and answers regarding late-winter or early-spring planted windbreaks (February-March) to help protect spring planted vegetable crops.

1)    Can winter rye, wheat, or barley still be planted in late-winter or early-spring as a windbreak? 

Yes, but there is a risk that it will not vernalize and produce stems and heads (may remain vegetative or short).

Winter-planted small grains such as winter rye and wheat will not produce stems and seed heads until after they have been exposed to cold temperatures. This exposure to cold temperatures, resulting in physiological changes in the plant, is called vernalization. The degree of vernalization required can vary by variety. Contrary to popular belief, the best vernalization temperatures are in the 40-50° F range, not at colder temperatures. For vernalization to occur, plants have to be biologically active (cool but above freezing).  Those plants that need vernalization require an additional environmental cue, change in day length, to ensure that flowering (heading) occurs in spring. The environmental cues of vernalization and day length change act together to promote spring flowering. Four to six weeks of 40-50°F temperatures are required for vernalization.

Past experience in Delaware has shown that winter wheat planted in late February or very early March will vernalize and be able to produce stems and heads.  Winter rye should also follow that pattern. It is critical to plant by March 1 to have the best chance of producing stems and not remain vegetative.  For these winter plantings, up your seeding rate to 150 pounds per acre.  Rye planted in February will be several weeks later to head and still may not provide full windbreak protection to April plantings.  Winter wheat, particularly southern bred varieties, may be more successful, especially moving into early March. 

2)    Are there other alternatives for March planted windbreaks?

Yes, spring oats, annual ryegrass and tall mustards are alternatives. 

As you go further into March, the chance of success with winter rye or wheat is reduced (it may remain vegetative with limited height).  The following is more information on alternatives to consider:

Spring Oats

Spring oats, planted as early as possible, is probably the best option for March plantings.  Use a high seeding rate (120 pounds per acre or more).  Oats will provide good ground cover and will head in late spring.  It will start to elongate in mid-May.  While still not an answer as a full windbreak for early plantings it will reduce sandblasting and provide protection for later plantings.  Height will be over 3’ at heading

Annual Ryegrass

Annual ryegrass will also produce significant growth from a March planting and provide soil cover.  Plant seeds at a rate of 30 pounds per acre.  Annual ryegrass can get as high as 3’ when producing seed heads but provides less of a windbreak.  One concern is with annual ryegrass is that if it goes to seed it has the potential to become a weed problem in the future.

Tall Mustards

There are several tall mustard varieties that merit considerations as windbreaks from March plantings.  These are “Idagold” mustard and “Pacific Gold” mustard.  As these mustards produce a flower stalk, they can reach a height of over 4’.  They are often used as biofumigant cover crops.  “Idagold” will reach full height and flower 55 days after planting and could possibly provide an April windbreak.  “Pacific Gold” also flowers at 55 days after planting and can also be over 4’ in height.  Plant at 10 pounds per acre.

Mixtures

Mixtures containing 2 or more of the crops mentioned above (spring oats, annual ryegrass, tall mustards) may be more desirable as a late winter or early spring planted windbreak.  Reduce seeding rates of each component by 1/3 in mixtures.

The University of Delaware Vegetable Extension Program will be doing research on windbreak alternatives for late-winter or early-spring planting in 2010.  We are seeking on-farm cooperators.  If you are interested, contact information is given below.

Gordon C. Johnson
Extension Vegetable and Fruit Specialist,

University of Delaware, Carvel Research and Education Center
16483 County Seat Highway, Georgetown, DE 19947
General Phone: (302) 856-7303, Direct Phone: (302) 856-2585 x 590, Cell Phone: (302) 545-2397, Fax: (302) 856-1845
Email: gcjohn@udel.edu

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.

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.

Powdery Mildew on Cucurbits

Friday, July 24th, 2009

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

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 fungicides (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 or Quintec* (quinoxyfen, 13) at 6.0 oz 2.08F/A plus chlorothalonil at 2.0-3.0 pt 6F/A.

*Quintec (quinoxyfen, FRAC code 13) from Dow AgroSciences has a section 3 supplemental label for powdery mildew control on pumpkin, winter squash and gourd. The label is available at http://www.rec.udel.edu/update09/Quintec.pdf.

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.