A commercially acceptable assessment technique for improved control of cabbage stem flea beetle feeding on winter oilseed rape

Highly significant relationships between the percentage of leaves showing Psylliodes chrysocephala (L.) feeding scars and the mean number of larvae per plant during autumn, were established from 457 fields (over five different years) in England and Wales, and used to define an index of leaf scarring as an alternative assessment method for control decisions. The index was tested in conjunction with autumn samples using datasets from 786 fields (six years). An action threshold of 50% leaves scarred resulted in similar treatment advice to the current plant dissection method in over 98% of cases. During spring, the relationship between percentage leaves scarred and mean number of larvae per plant was not consistent between years and the index cannot be used for population assessment at this time of year.