Tag Archives: Cucurbits

Time to Start Scouting for Powdery Mildew

This is a re-post from 2016 – Late-July to early-August is the key time for powdery mildew management!  With any disease, preventative management provides the best control.

Powdery mildew typically arrives in Southern Ontario in mid-to-late July. Plants are most susceptible to infection during the fruit sizing and development. Poor control results in decreased yield and poor fruit quality at harvest. The threshold for treatment is 1 lesions/50 plants. Optimum powdery mildew control is a combination of variety selection, fungicide timing and fungicide selection.

Powdery Mildew Lesion on the Lower Leaf Surface
Powdery Mildew Lesion on the Lower Leaf Surface

Cheryl Trueman, a vegetable pest management researcher at the University of Guelph’s Ridgetown Campus, has been conducting powdery mildew efficacy trials since 2009. In these trials, several products consistently provided good control of powdery mildew. These products are powdery mildew targeted, and have a single site mode of action. To prevent the development of resistance, it is essential to always rotate between different fungicide groups and/or tank mix with a broad spectrum fungicide.

Powdery Mildew Targeted Fungicides Showing Consistent Control in the Ridgetown Field Trials:

Group 13: Quintec (quinoxyfen)
Quintec was the most consistent powdery mildew product tested in Ridgetown. It provided excellent control in 4/5 years and good control in 1/5 years tested.

Group U8: Vivando (metrafenone)
Vivando provided excellent control in 1/3 years and good control in 2/3 years and tested.

Group 7: Fontelis (penthiopyrad), Aprovia (benzovindiflupyr), Sercadis (fluapyroxad) and Pristine (boscalid/pyraclostrobin).
Fontellis was somewhat less consistent. Control with this produce ranged from excellent to poor, depending on the year. It provided excellent control in 1/5 years, good control in 2/5 years and poor control in 2/5 years. Note: Aprovia, Sercadis and Pristine were not tested in the Ridgetown Campus trials.

Group 3: Inspire (difenoconazole), Proline (prothioconazole) and Quadris Top (azoxystrobin/difenoconazole)
Inspire provided a level of control similar to Fontelis; good control in 3/5 years, and poor control in 2/5 years. Proline and Quadris Top were only tested for one year in the Ridgetown trials, in which they both provided good control.

Fungicides containing chlorothalonil (Bravo ZN and Echo) provided a lower level of powdery mildew control, but are still better than the untreated checks. They also control a broad range of other foliar diseases including scab and alternaria.

Research in Ontario and other jurisdictions indicates that the group 11 (QoI) fungicides, Cabrio (pyraclostrobin) and azoxystrobin (a component of Quadris Top) no longer control powdery mildew. However, they may provide control of other cucurbit diseases such as anthracnose and alternaria.

Additional reading: http://www.omafra.gov.on.ca/IPM/english/cucurbits/diseases-and-disorders/powdery-mildew.html#advanced

Time to Start Scouting for Powdery Mildew

Powdery mildew typically arrives in Southern Ontario in mid-to-late July. Plants are most susceptible to infection during the fruit sizing and development. Poor control results in decreased yield and poor fruit quality at harvest. The threshold for treatment is 1 lesions/50 plants. Optimum powdery mildew control is a combination of variety selection, fungicide timing and fungicide selection.

Powdery Mildew Lesion on the Lower Leaf Surface
Powdery Mildew Lesion on the Lower Leaf Surface

Cheryl Trueman, a vegetable pest management researcher at the University of Guelph’s Ridgetown Campus, has been conducting powdery mildew efficacy trials since 2009. In these trials, several products consistently provided good control of powdery mildew. These products are powdery mildew targeted, and have a single site mode of action. To prevent the development of resistance, it is essential to always rotate between different fungicide groups and/or tank mix with a broad spectrum fungicide.

Powdery Mildew Targeted Fungicides Showing Consistent Control in the Ridgetown Field Trials:

Group 13: Quintec (quinoxyfen)
Quintec was the most consistent powdery mildew product tested in Ridgetown. It provided excellent control in 4/5 years and good control in 1/5 years tested.

Group U8: Vivando (metrafenone)
Vivando provided excellent control in 1/3 years and good control in 2/3 years and tested.

Group 7: Fontelis (penthiopyrad), Aprovia (benzovindiflupyr), Sercadis (fluapyroxad) and Pristine (boscalid/pyraclostrobin).
Fontellis was somewhat less consistent. Control with this produce ranged from excellent to poor, depending on the year. It provided excellent control in 1/5 years, good control in 2/5 years and poor control in 2/5 years. Note: Aprovia, Sercadis and Pristine were not tested in the Ridgetown Campus trials.

Group 3: Inspire (difenoconazole), Proline (prothioconazole) and Quadris Top (azoxystrobin/difenoconazole)
Inspire provided a level of control similar to Fontelis; good control in 3/5 years, and poor control in 2/5 years. Proline and Quadris Top were only tested for one year in the Ridgetown trials, in which they both provided good control.

Fungicides containing chlorothalonil (Bravo ZN and Echo) provided a lower level of powdery mildew control, but are still better than the untreated checks. They also control a broad range of other foliar diseases including scab and alternaria.

Research in Ontario and other jurisdictions indicates that the group 11 (QoI) fungicides, Cabrio (pyraclostrobin) and azoxystrobin (a component of Quadris Top) no longer control powdery mildew. However, they may provide control of other cucurbit diseases such as anthracnose and alternaria.

Additional reading: http://www.omafra.gov.on.ca/IPM/english/cucurbits/diseases-and-disorders/powdery-mildew.html#advanced

Cucumber Downy Mildew Confirmed in Kent County, Ontario

July 5th, 2016: cucurbit downy mildew was identified today in a processing cucumber field in Kent County, Ontario.  Now that the disease is present in the great lakes region, growers should immediately move to a targeted downy mildew spray program.

See the 2016 Downy Mildew Control Strategy for Cucumber Crops for an up-to-date list of registered control products.

Use only the downy mildew targeted products listed in the strategy. Research trials in Ridgetown, Simcoe and in the neighbouring states have shown these products to be the most consistent from year-to-year.

Rotate between all three of the targeted downy mildew products, starting with the most effective product, Orondis Ultra, and then rotate to either Zampro or Torrent within 7-days.

If you have any questions about the cucumber downy mildew control strategy, please call 519 674 1616 or email elaine.roddy@ontario.ca

Cucumber Downy Mildew Update – June 14th, 2016

Do date there have been no confirmed reports of downy mildew in the Great Lakes region.  However, activity does continue in the Southern US.  The ipmPIPE website tracks the epidemic (figure 1) and also forecasts the potential spread of the disease.

2016-06-16_CDMepidemicstatus
Cucurbit Downy Mildew Epidemic Status Map, 2016-06-14

Historically, downy mildew has arrived in this area in late-June to early July. We have found that using an early broad spectrum preventative fungicide program, staring at vine development, will result in better season long control of the disease. This is especially important if weather conditions turn wet and overcast, with storm originating in the Southern US.

For complete details see the 2016 Downy Mildew Control Strategy for Cucumber Crops.

If you suspect downy mildew in your cucurbit crop, please notify OMAFRA, your agri-business supplier or your grading station.  Downy mildew is a community disease and open communication is vital to ensuring a healthy crop.

2016 Downy Mildew Control Strategy for Cucumber Crops

The 2016 Downy Mildew Control Strategy for Cucumber Crops contains an updated list of fungicides, including the newly registered Orondis Ultra. The restricted entry interval for Bravo has also been updated to reflect the new Bravo ZN label.

Due to the development of resistance and concerns about efficacy, Tattoo C and Presidio have been removed from the 2016 strategy. These products may provide  suppression under low risk conditions, however research results indicate that they are not sufficient controls under higher disease pressure.

For more reading:

Research Update – Fungicide Efficacy on Downy Mildew in Cucumbers

Ontario CropIPM – Downy Mildew

Angular, tan-to-brown lesions caused by cucurbit downy mildew
Cucurbit Downy Mildew

 

Pumpkins and Squash Disease Update: 15-Aug-2105

Downy Mildew – While downy mildew is a common occurrence in cucumbers, it is less so in pumpkins and squash.  However, growing regions across eastern North American are experiencing unusually high pressure from downy mildew in all cucurbit crops this year.  Symptoms and spores were recently identified in a pumpkin field in Norfolk county.  While the disease is typically less aggressive in pumpkins and squash than it is in cucumbers, it is still a good idea to scout fields regularly for symptoms.  If the scouting results show that the levels of disease are increasing, downy mildew targeted sprays may be warranted to keep later-maturing crops healthy.  Keep in mind that fungicides commonly used for powdery mildew control will not control downy mildew.

Powdery Mildew – powdery mildew is active in most pumpkin fields by now.  Fungicides must be applied at the very early stages of this disease in order to be truly effective.  Once symptoms are readily visible on the upper-leaf surface, it is usually too late to really benefit from control measures.  When scouting, look for white, powdery spores on the lower surface of the leaf.  There may be a corresponding light-green or yellow lesion on the top surface.  Symptoms usually first appear on the mid-portion of the plant, or even the petioles.

Powdery Mildew Lesion on the Lower Leaf Surface
Figure 1. Powdery Mildew Lesion on the Lower Leaf Surface