Check crops for phoma urges IACR
28 September 2001
Check crops for phoma urges IACR
OILSEED rape growers are being urged to check crops for phoma leaf spotting this weekend.
The warning comes from national disease expert Bruce Fitt of IACR Rothamsted who says recent spore trapping indicates significant ascospore release last Wed, Sept 19. Leaf spotting normally appears around 10 days later and can lead to yield-sapping stem cankers.
This years first release was 10 days earlier than last year and larger, releasing two thirds more ascospores, he notes. Prolonged wet weather during summer, which kept debris constantly damp, is the primary cause.
"Crops most at risk are small plants showing early signs of infection. On these high risk crops or where there is more than 20% leaf spotting then growers must spray at the earliest opportunity," he says. Alternate wet and dry weather favours ascospore release. *