Incidence of the major Brassica pests in northwestern Spain.

Kale (Brassica oleracea L. acephala group) crops are common in northwestern Spain, where they are severely damaged by different insect pests. The damage notably affects the value of this crop because it is freshly consumed and fresh processed. The objective of this work was to determine the abundance and relative importance of the main Lepidoptera pests of Brassica crops for 6 yr at five localities in northwestern Spain and to relate the seasonal changes of larval populations and environmental conditions. Pheromone traps were used as a method of monitoring adults. Larval populations were monitored on kales by counting the larvae for several years and locations at different sample dates. Five species were found: Mamestra brassicae (L.); imported cabbageworm, Pieris rapae (L.); Pieris brassicae (L.); diamondback moth, Plutella xyllostella (L.); and Autographa gamma L. Proportions of each insect fluctuated over the years and in the different locations. M. brassicae was the most abundant (48.5% of the total of Lepidoptera species) followed by P. xyllostella (25%) and P. rapae (15%). The use of pheromone traps combined with plant sampling permitted the detection of two generations of M. brassicae. However, adult counts were not correlated to the number of larvae on plants.