News and Tips for You
July 31 2011
Sclerotinia stem rot
The last map of the 2011 growing season has been uploaded. By this time, most fields have already finished the flowering period and thus are out of danger. The disease-conducive weather prevalent in some areas for this period may result in light Sclerotinia infection on canola that has been heavily lodged. Canola plants that are standing straight should not have problems.
July 28 2011
Sclerotinia stem rot
Risk of Sclerotinia stem rot
Risk of Sclerotinia development for most canola growing regions for July 28, 2011 has increased in many parts of the canola growing areas of the region. This is in response to cooler temperatures and the precipitation experienced in previous days. While favorable conditions are still of concern, growers should keep in mind that fields that are past full bloom or have ended flowering altogether, are no longer at risk of high infection. Fungicide applications in those fields are not recommended because they usually do not provide an economic return.
Lodging and Sclerotinia stem rot
While fields that have finished the flowering stage are out of danger of major infection, very light yield losses could be experienced in areas of the fields where the plants are heavily lodged. Lodged plants help maintain humidity in soil and air under the canopy for long times and thus favor apothecia formation as well as infection of plants. Under this condition, the fungus can move from plant to plant; however, the movement will be mostly limited to the lodged plants and only very light yield reductions could occur. Fungicide applications to control Sclerotinia on lodged plants that have passed the flowering stage are not recommended.
July 25 2011
Sclerotinia stem rot
Risk of Sclerotinia development for most canola growing regions for July 25, 2011 is low. While precipitation continues to fall in some canola growing regions, at this point fields planted by June 1st are already in the late flowering stages or have entered the ripening stage. Therefore, the risk of new infections by Sclerotinia is low and fungicide applications are not recommended.
Fields planted by June 7th in Bottineau, Cavalier, Mountrail, and Rolette counties in North Dakota, and Kittson and Pennington counties in Minnesota are in the early stages of flowering. Risk of Sclerotinia for Bottineau and Rolette counties is low at this time. Cavalier County has intermediate risk, but Mountrail, Kittson, and Pennington counties are at high risk at this point. Growers in these counties are urged to check the risk calculator to help in their decision regarding fungicide applications.
July 20 2011
Sclerotinia stem rot
Risk of Sclerotinia development for most canola growing regions for July 20, 2011 is low. The high precipitations recorded in the initial days of the heat wave caused the risk to remain high for certain areas; however, the absence of significant precipitation in the past three days has negated the impact of the precipitation and brought down the risk in most areas. The warm temperatures experienced in the past few days have also helped speed up the flowering process. The estimated flowering stage of fields planted at three different dates has been calculated using NDAWN data.
Canola growth stages and risk of Sclerotinia
Fields planted by May 24th have for the most part finished the flowering stage and are entering now the early ripening stages. The window for infection by Sclerotinia has ended for these fields.
Fields planted by June 1st are passing the 50% bloom stage in most locations. For most of these fields the risk of Sclerotinia infection is closing and fungicide applications made from this point on will not produce economic returns.
Fields planted by June 7th are in the early stages of flowering and thus at the most susceptible stage for infection by Sclerotinia. Growers with fields at this stage are encouraged to check the estimated risk of Sclerotinia development and the risk calculator when deciding whether to spray or not.
July 18 2011
Sclerotinia stem rot
While high risk areas still persist in canola growing regions of the state, this is a clear response to the heavy precipitation experienced during the weekend in those areas. For most other locations, however, the combination of high temperature and low precipitation has reduced the risk of disease development as expected. The added heat units will help many fields speed up the flowering process and escape damage by Sclerotinia.
If you decide to make a fungicide application, remember that the best time to spray your product is when the plants are between 30% and 50% bloom. In general, plants are at 20% bloom when they have approximately 15 open flowers on main stem. This stage is reached usually within six days from the time the first flower opens and is heavily influenced by temperature. Warmer temperatures usually speed up the flowering process. Plants at 30% bloom have 20 or more flowers open on main stem; at this stage, there is little to no petals dropped and no pods are forming. This stage could be reached within 2 or three days from 20% bloom. When plants reach 50% bloom, they usually have at least 20 flowers open on the main stem and lateral branches have started to flower already. At this stage the fields reached their maximum color intensity. At that stage pods are evident. Fungicide applications after plants have reached the 50% bloom stage usually do not provide an economic return.
For an illustrated guide of canola bloom stages please see NDSU extension publication PP-1410
July 15 2011
Sclerotinia stem rot
Recent rain events and moderate temperatures have increased the risk of disease development in several canola growing regions in northern North Dakota. However, this situation may not last long. The national weather service is forecasting high temperatures for this weekend and the next several days. Temperatures greater than 85 F inhibit growth of Sclerotinia and delay disease development. While high temperatures will not kill the fungus, they will allow the crop to escape damage at its most sensitive stage, the initial stages of flowering. So as temperatures increase over the weekend, expect the risk of Sclerotinia development to decrease.
Remember that to obtain the best response of a fungicide application the product should be applied when plants are between 30 and 50% bloom. Fungicide applications past that stage usually do not provide an economic return.
July 12 2011
Sclerotinia stem rot and risk calculator
Recent rain events have increased the risk of Sclerotinia development in many canola growing areas of the state and in the Roseau area in Minnesota. Canola growers, especially those from areas in which intermediate risk levels are calculated, are encouraged to use the risk calculator from this website to obtain a more accurate estimation of the risk in their fields.
While registration is necessary to use the calculator, the registration is free and growers can use the calculator as frequently as they need. Once logged in, growers will be asked a few questions related to cultural practices in their fields. Answers will be combined with information from the nearest weather station and the risk will be recalculated.
Keep in mind that estimations of risk apply only to canola fields that are starting to flower or are in early stages of flowering.
Fungicides registered for control of Sclerotinia stem rot in North Dakota are: azoxystrobin (Quadris), boscalid (Endura), metconazole (Quash), prothioconazole (Proline), pyraclostrobin (Headline), and tiophanate methyl (Topsin). Also, the biological control compounds Serenade, and Polyversum are registered for use against Sclerotinia in foliar applications. For application rates consult your extension agent.
July 5 2011
Sclerotinia stem rot
As of July 3, 2011 the only areas at high risk of Sclerotinia were around the Bottineau NDAWN station. Most other areas of the state were at low to moderate risk. This is the result of the high temperatures recorded in previous days. However, this forecast may change in the near future if cooler weather returns. Also, remember that this information applies only to fields that have canola in the initial flowering stages.
June 17 2011
Sclerotinia stem rot
Many fields were planted rather late in the season due to continued rains that prevented growers from getting into the fields. This has resulted in numerous fields with canola seedlings that have not reached the 6th leaf stage yet. This late planting could have some implications for disease development. Prolonged wet soil conditions in the past weeks are already contributing to conditioning sclerotia for apothecia production and that is reflected in the current risk map. Risk estimation for fields entering flowering period by June 17 is moderate for most of the canola growing areas in North Dakota and Minnesota. If warmer but wet conditions prevail in the next several days, the risk of disease development could increase for these fields.
Fungicides registered for control of Sclerotinia stem rot in North Dakota are: azoxystrobin (Quadris), boscalid (Endura), metconazole (Quash), prothioconazole (Proline), pyraclostrobin (Headline), and tiophanate methyl (Topsin). Also, the biological control compounds Serenade, and Polyversum are registered for use against Sclerotinia in foliar applications. For application rates consult your extension agent.
Blackleg
The combination of cool and wet conditions that kept growers from planting canola on time are enhancing production of blackleg inoculum. Showers of blackleg spores that otherwise could have landed on plants with more than 4-6 true leaves, may now be landing on younger seedlings enhancing the risk of blackleg development. Volunteer canola plants in fields not planted are already showing blackleg symptoms in some areas of the state, an indication that inoculum is being actively produced. Growers with canola seedlings that have not reached the 4-6 leaf stage in fields located in close proximity to fields that had severe blackleg problems in 2010 should consider protecting their fields with fungicides. Keep in mind, however, that if your canola plants are past the 4-6 leaf stage fungicide applications will not be as effective.
Currently, the only products registered for use against blackleg are azoxystrobin (Quadris) and pyraclostrobin (Headline). If azoxystrobin (Quadris) is used for blackleg control, grower should avoid using it to control Sclerotinia in the same growing season. Multiple applications of this compound in the same growing season could increase the risk of development of resistance to the fungicide.
