Sclerotinia Monitoring

Sclerotinia is a common disease of oilseed rape and with closer rotations the disease risk is now increasing. There are some very severe attacks each year, where more than 20% of plants are affected. Yield of affected plants is halved, because of premature ripening. There are well-recognised hotspots of Sclerotinia in the South East and West Midlands in England and Scotland, but severe attacks can occur in most regions of the UK.

A well-timed fungicide spray is usually able to achieve at least 80% reduction in stem rot. Fungicides should be used as protectant treatments, before petal sticking has occurred. The optimum timing is often at early to mid-flowering.

ADAS and BASF have run a service for the past six years, which has proved a popular management tool, to help advisors and growers, assess the disease risk and optimise treatment timing.

Advisors and growers are invited to log on to track Sclerotia germination in their region, to assess disease risk. There will be a bulletin issued every week, for twelve weeks.

The map shows the locations of 6 sites where we are collecting data to monitor the extent of sclerotina:

• June 4th 2010 (40.56 KB)
  Published Date: Monday 7th June 2010

  This is the last bulletin of the monitoring programme for the 2010 spring season.

  Overview: Most crops are at the end of flowering and are almost green overall with full sized seeds in the lower pods. There are some crops of later flowering varieties that are still flowering quite strongly (BBCH 67-79). Crops that have suffered loss of flower buds are expected to recover and produce new flowering shoots. Very backward crops and pigeon damaged areas are still at mid flowering (BBCH 61). Some sclerotinia symptoms have been found in the Hereford area with about 1% plants affected. Germination of sclerotinia has continued during the last week, helped by some rain. Night temperatures are generally above 7°Cand with humid weather after rain, the infection risk is now at its highest for the season to date. The greatest sclerotial germination (59%) is on Romney Marsh, Kent.  Petal tests have shown over 70% infection at the North Yorkshire site, but there are also some high counts in all regions. This indicates that spores could well be present in quite large numbers at high risk sites.

   

  Crops that are still flowering strongly may still require a fungicide spray but treatments are complete on most crops. Fungicides should provide good protection against sclerotinia for about 3 weeks. A second spray should be considered where the first spray was applied 3 weeks ago and flowering is likely to continue for at least 10 days. Spring rain and peas are likely to be at risk if the weather is unsettled or wet.

   

  
  
• May 21st 2010 (39.74 KB)
  Published Date: Monday 24th May 2010

  Overview: Most crops are at mid to late flowering and are setting pods (BBCH 67). Some crops have finished flowering on the main raceme but still have flowers on the branches. Some crops of later flowering varieties such as DK Cabernet or later crops of other varieties have suffered severe loss of flower buds which has been attributed mainly to low temperatures. Affected crops are expected to recover and produce new flowering shoots. Very backward crops and pigeon damaged areas are still barely flowering (BBCH 61). Sclerotinia is germinating at all sites now. As night temperatures are likely to be above 7°C, the infection risk is now at its highest for the season to date. Rainfall has been variable during the last week, but some infection may have taken place, particularly in the south. The first sclerotinia stem rot has been found in Hereford but levels are very low. The greatest sclerotial germination (54%) is on Romney Marsh, Kent with Devon close behind (42%) this week. Petal tests have shown over 47% sclerotinia infection (in Hereford and Kent), but there are also some high counts in all regions at high risk sites. This indicates that spores could well be present in quite large numbers at high risk sites.

   

  The sclerotinia risk is increasing because of higher sclerotial germination, petal fall in most crops and night temperatures reaching the  7°C threshold for plant infection. Long periods of high humidity are also required for infection – keep watching for more rain.  Fungicides applied at the yellow bud stage should provide some protection against sclerotinia during early flowering. The main sclerotina spray can then be applied about 3 weeks later at the mid-flowering stage. It looks like it will be a late epidemic (if there is one) this year.

   

  
  
• May 14th 2010 (39.22 KB)
  Published Date: Thursday 13th May 2010

  Overview: Most crops are in full flower with many having almost all flowers open on the main raceme (BBCH 67) and pods are setting. Early flowering varieties will soon be finished flowering (BBCH 79). Very backward crops and pigeon damaged areas are still barely flowering (BBCH 61). Rain last weekend and subsequent showers are keeping soils moist so sclerotinia is germinating quite rapidly at some sites in the south. There appears to have been little petal stick so far and with night temperatures not reaching 7°C, infection to date is likely to be low. With warmer nights, infection could start at any time. Soil temperatures are now dipping below 10°again. Sclerotia have now started to germinate in all the depots except at Boxworth. The greatest germination (47%) is on Romney Marsh, Kent with Devon close behind (41%) this week. Petal tests have shown over 47% sclerotinia infection (in Hereford and Kent), but there are also some high counts in the east and Lincs at high risk sites. This indicates that spores could well be present in quite large numbers at high risk sites.

   

  The sclerotinia risk is increasing because of higher germination, petal fall in most crops and the forecast of rain. Night temperatures have been unusually low recently but as soon as they reach 7°C plant infection could occur. Fungicides applied at the yellow bud stage should provide some protection against sclerotinia during early flowering. The main sclerotinia spray can then be applied about 3 weeks later at the mid-flowering stage. The potential is for a late epidemic this year.

   

  
  
• May 7th 2010 (38.74 KB)
  Published Date: Friday 7th May 2010

  Overview: Most crops are in full flower with many having almost all flowers open on the main raceme (BBCH 67) and pods are setting. Later flowering varieties still have buds on the main raceme (BCH 65). Very backward crops and pigeon damaged areas are still at the green bud to buds raised above the leaves stages (BBCH 53). Rain at the Bank Holiday weekend is helping crops and sclerotinia though there appears to have been little petal stick so far. With night temperatures only occasionally reaching 7°C, infection to date is likely to be low. With warmer nights, infection could start at any time. Soil temperatures are now above 10°, but are still likely to fluctuate with colder nights continuing. Sclerotia have now started to germinate in all the depots except at Boxworth. The greatest germination (29%) is in Devon this week. Petal tests have shown up to 47% sclerotinia infection (in Hereford), but there are also some high counts in the south and east at high risk sites. This indicates that spores could well be present in quite large numbers at high risk sites.

   

  The sclerotinia risk is increasing because of higher germination, petal fall in forward crops and the forecast of rain. Night temperatures are sometimes above 7°C which is the threshold for plant infection to occur. Fungicides applied at the yellow bud stage should provide some protection against sclerotinia during early flowering. The main sclerotina spray can then be applied about 3 weeks later at the mid-flowering stage.

   

  
  
• April 30th 2010 (38.04 KB)
  Published Date: Tuesday 4th May 2010

  Overview: Most crops are between early and mid- flowering (BBCH 61-65) with obvious differences between early and later flowering varieties. Very backward crops and pigeon damaged areas are still at the green bud to buds raised above the leaves stages (BBCH 53). There is considerable patchiness in some crops particularly in the east, which now shows up strongly as variation in flowering. Soil temperatures are still fluctuating but starting to get above 10°C. Sclerotia have started to germinate in the depots in Devon and Hereford this week. This follows previous germination reports at Rothamsted and Hereford that were not in the depot network. With more rain, germination could start at other depots were conditions are drier than in the west. The first petal tests have shown up to 37.5% sclerotinia infection (in Devon), but there are some high counts in the eastern sector (30% petal infection) at high risk sites though 5% is more typical. This indicates spores could well be present in quite large numbers at high risk sites, particularly in the south and west.

   

  The sclerotinia risk is increasing because of higher germination, petal fall in forward crops and the forecast of rain. Night temperatures are sometimes above 7°C which is the threshold for plant infection to occur. Fungicides applied at the yellow bud stage should provide some protection against sclerotinia during early flowering. The main sclerotina spray can then be applied about 3 weeks later at the mid-flowering stage.

   

  
  
• April 23rd 2010_edit (37.46 KB)
  Published Date: Friday 23rd April 2010

  Overview: Many crops are at or close to early flowering (BBCH 61) with more still at the yellow bud stage. Development has slowed slightly in response to the lower temperatures. Very backward crops and pigeon damaged areas are still at the green bud stage (BBCH 53). There is considerable patchiness in some crops which now shows up strongly as variation in flowering. There is also large variation in plant size within crops. Cold nights are continuing and soil temperatures are still fluctuating and struggling to get above 9°C. Sclerotia have started to germinate in the east (at Rothamsted) and become more active in the west (Hereford) but not in the depot network. The first petal tests are still incomplete but we can already see 30% infection at the Devon site and some at the Hereford site. This indicates spores could well be present in quite large numbers at high risk sites, particularly in the south and west.

   

  Early sclerotinia sprays are now being applied to some crops. The sclerotinia risk generally low at present as night temperatures are mainly below 7°C and little germination of sclerotia is evident. The occasional infection period has been forecast during the last week. However, some rain and higher temperatures are needed to boost germination and increase the risk from sclerotinia. Fungicides applied at the yellow bud stage should provide some protection against sclerotinia during early flowering. The main sclerotinia spray can then be applied about 3 weeks later at the mid-flowering stage.

   

  
  
• April 16th 2010 (34.88 KB)
  Published Date: Friday 16th April 2010

  Overview: Some crops are at early flowering but more are at the yellow bud stage. Most crops are at or beyond the growth stage where flower buds raised above the leaves (GS 3,5). Crops are mainly in the range 50-80 cm tall, though there is a large variation in plant height within crops. There is considerable variation in growth and development within many fields. Stunted plants and low populations are evident where there has been pigeon grazing. Cold nights are continuing but soil temperatures have started to increase again. Sclerotia have started to germinate in the east (at Rothamsted) and in the west (Hereford) but not in the depot network.

   

  As some crops are now at or close to the yellow bud stage, plans are being made to use Plant Growth Regulators (PGRs) and/or early sclerotinia sprays. The sclerotinia risk generally low at present as night temperatures are below 7°C and little germination of sclerotia is evident. However, with some rain and higher temperatures, the risk from sclerotinia could increase. Fungicides applied at the yellow bud stage should provide some protection against sclerotinia during early flowering. The main sclerotina spray can then be applied about 3 weeks later at the mid-flowering stage.

   

  
  
• April 9th 2010 (34.10 KB)
  Published Date: Thursday 8th April 2010

  Overview: The first few flowers are present in the more forward crops but the main growth stage is flower buds raised above the leaves (GS 3,5). Crops are mainly in the range 30-60 cm tall. Colder weather during the last week has resulted in a fall in soil temperatures and this is holding back germination of sclerotinia. The first sclerotia started to germinate in late March last year.  If soil temperatures increase, sclerotia could soon start to germinate. As there is considerable winter damage to the older leaves this season, this may enable sclerotinia to infect leaves and cause some early stem rot before flowering.

   

   

  Crops are now at or close to the mid-stem extension stage. PGR fungicide application could be delayed until the yellow bud stage. This will still have a big impact on reducing canopy size and improving yields and it also provides some protection against sclerotinia during early flowering. This could be especially relevant considering the increased risk from sclerotinia following the 2007 and 2008 epidemic.  The main sclerotina spray can then be applied about 3 weeks later at the mid-flowering stage.

   

  
  
• March 31st 2010 (33.71 KB)
  Published Date: Wednesday 31st March 2010

  Overview: Flower buds are visible from above (the green bud stage) in many crops though some have flower buds raised above the leaves (GS 3,5). Crops have doubled in height during the last week and most are in the range 15-30cm tall. Colder weather in the last few days may slow growth and development of plants and sclerotinia. Soils are moist at the surface so it is low soil temperatures that are holding back germination of sclerotinia. The first sclerotia started to germinate in late March last year.  If soil temperatures increase during Easter, sclerotia could soon start to germinate. As there is considerable winter damage to the older leaves this season, this may enable sclerotinia to infect leaves and cause some early stem rot before flowering.

   

  There is still an urgent need to check for light leaf spot in all crops. Symptoms are now easy to find in crops that had no symptom a month ago. High levels are present in some crops in all regions even where fungicides were applied last autumn. Treatments should be applied as soon as possible – a threshold of 15% plants affected is suggested as this should equate to a 5% or 0.2 t/ha yield response.

   

  
  
• March 26th 2010 (33.44 KB)
  Published Date: Friday 26th March 2010

  Overview: Flower buds are visible from above (the green bud stage) in some crops though most crops are close to the early stem extension stage (GS 3,1; BBCH 50). Diffuse leaf purpling attributed to cold and nitrogen deficiency is very common, but stronger leaf purpling may well be caused by Turnip yellows virus   There has been no germination at any of the depots so far this season. With rain in most areas during the last week and rising soil temperatures, sclerotia could soon start to germinate.

   

  There is an urgent need to check for light leaf spot in all crops. Symptoms are now easy to find in crops that had no symptom a month ago. High levels are present in some crops in all regions even where fungicides were applied last autumn. Treatments should be applied as soon as possible – a threshold of 15% plants affected is suggested as this should equate to a 5% or 0.2 t/ha yield response.

   

  
  
• March 18th 2010 (33.84 KB)
  Published Date: Friday 19th March 2010

  Overview: Crops are only just starting to make new growth and are 10-30cm shorter than crops at the same date last year. Plants are at the flower buds enclosed stage (GS 3,1; BBCH 50). Diffuse leaf purpling attributed to cold and nitrogen deficiency is very common, but stronger leaf purpling may well be caused by Turnip yellows virus   There has been no germination at any of the depots so far this season. Soils have a good frost mould and have been drying at the surface. With rain due at the weekend, sclerotia could start to germinate as soil temperatures rise.

   

  There is an urgent need to check for light leaf spot in all crops. High levels are present in some crops in all regions even where fungicides were applied last autumn. Treatments should be applied as soon as possible – a threshold of 15% plants affected is suggested as this should equate to a 5% or 0.2 t/ha yield response.