Despite the hot, dry conditions, levels of asparagus rust are increasing in young plantings. Foliar disease management is important in all asparagus plantings. However, fields are particularly susceptible to infections during the first few years of establishment, causing a reduction in productive crown development.
Even in established asparagus fields, rust can have a significant impact on both the spear weight and spear number.
Warm weather with heavy dew, fog, or light rainfall enhances rust development. Infection can occur with as few as 3-9 hours of leaf wetness.
All foliar fungicides are most effective when they are applied before symptoms begin to move into the upper crop canopy. Thorough coverage is essential for good 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.
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.
Rebecca Shortt, Engineer – Water Quantity, OMAFRA – Simcoe
Are you concerned that your irrigation system is not applying enough water? too much water? or applying unevenly? To request an Irrigation System Assessment contact Rebecca Shortt, OMAFRA Water Quantity Engineer at 519-426-4920 (limited availability).
Australian research has shown that one of the greatest opportunities for irrigation water savings are in improving how evenly the water is spread across the field by the irrigation system. Continue reading Irrigation system assessments→
To date, I know of no confirmed cases of late blight in Ontario, but it has been found on potato in Branch County, Michigan (south of Battle Creek). Nevertheless, our experience of recent years would indicate we are likely to see it in Ontario tomatoes at some point in the season.
Remember that conventional tomato growers using a recommended fungicide program for early blight, septoria leaf spot, and anthracnose, are also protecting the crop from late blight infection. Cloudy and high humidity or wet conditions are favourable for late blight. The pathogen prefers cool temperatures. The disease is suppressed by hot, dry weather, but it can continue developing and spreading when suitable conditions return.