2005/2006 SURVEY: SUMMER ASSESSMENT 2006
| Stems and pods of twenty-five plants from each surveyed crop were
assessed visually at pod ripening for symptoms of disease. |
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The proportion of crops affected with Phoma canker was 94.9% in 2006 compared with 93.7% in summer 2005. Incidence in both 2005 and 2006 was much higher than the
long term mean recorded between 1995 and 2004 of 48.0% crops affected. Total phoma (including cankers and stem lesions)
was recorded this year at 53.2% stems affected. This is higher than in previous years when 39% stems were affected
in 2005 and a long-term mean (1995 and 2004) of 43% stems affected.
Phoma canker was found in nearly half of all the plants in the 2006 survey, with 45.7% affected.
Phoma pod spot also increased in incidence this year with 13.5% crops affected
and 1.2% plants affected compared with 2.3% crops and 0.1% plants last year.
- Levels of light leaf spot were higher than in recent years. Light leaf spot on the stems affected
46.4% crops compared to 23.2% in summer 2005. 28.1% crops had symptoms on the pods this year, compared
with 16.1% last year. In both 2005 and 2006, levels of light leaf spot on the stems and pods have been lower
than the 1995 to 2004 mean of 57.4% crops with stems affected and 35.7% crops with pods affected.
in 2006, light leaf spot was found in all regions on both the stems and pods, with
the highest incidence being recorded in the North and South West regions.
- The incidence of dark pod spot (Alternaria spp.) was lower than last year with 70.8% crops
affected compared with 85.1% last year. However, this was still higher than the long term mean between
1995 and 2004 of 61.8% crops affected. The highest incidence of dark pod spot was
recorded in the South East region and the lowest in the North.
- Sclerotinia stem rot was recorded in all regions with a mean incidence of 20.6% crops and 2.4% stems
affected. This was higher than the previous year when 17.9% crops and 1.9% plants were affected, and higher that the
long term mean (1995-2004) when 17.9% crops and 1.8% plants were affected. As in summer 2005,
the highest incidence of Sclerotinia stem rot was recorded in the South West region.
- The incidence of Botrytis on both the stems and the pods was much lower this year compared with the
summer of 2005. On the pods, Botrytis affected 33.7% crops and 7.7% plants compared to 92.0% crops and
39.5% plants last year. On the stems, 6.2% crops and 0.4% plants were affected, compared with 10.5% crops
and 1.2% plants in 2005. Between 1995 and 2004, Botrytis on the stems affected a mean of 14.2% crops and 1.0% plants,
and on the pods 25.4% crops and 6.1% plants.
- The incidence of powdery mildew on the stems was slightly lower than in summer 2005, with 29.9% crops
and 12.1% plants affected, compared to 36.8% crops and 13.6% plants. Less crops had affected pods, with
24.7% compared to 31.0% in 2005, but incidence within crops was higher with 7.1% plants affected compared
to 5.8% in 2005. Levels of powdery mildew were similar to the long term mean of 23.4% crops with pod symptoms
and 16.3% crops with stem symptoms.
- Compared to 2005 when downy mildew was not recorded in the survey in the summer, downy mildew on the
pods was recorded this year at 4.5% crops and 0.9% plants affected. However, this is still much lower
than the mean level of 27.7% crops affected between 1995 and 2004. Downy mildew was not
found on any of the stems surveyed in 2006, it has not been recorded on stems in the survey since 1991.
- White leaf spot was not recorded on the pods in any region. It has not been recorded on any pods
in the survey since 1999.
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Incidence of diseases on the pods - % plants affected
Incidence of diseases on the stems - % plants affected
Regional incidence of diseases on the pods - % plants affected
Regional incidence of diseases on the stems - % plants affected
