Expansion of pea cropping increases the risk of pea moth (Cydia nigricana; Lep., Tortricidae) infestation

Abstract:  The pea moth ( Cydia nigricana ) is a host-specific pest of pea ( Pisum sativum ). In Finland, the combine-harvested field pea is grown on an area totalling 5000 ha. However, the area under pea cropping may increase substantially if pea replaces soya bean as a protein source for animal feed, which may result in pest and disease problems. In this study, the risk of pea moth infestation is evaluated by modelling field survey data. The observations were made in 2002 and 2003 at 93 and 90 pea fields, respectively, in south-western Finland. The choice of the experimental fields was based on pea cropping data from 1997 to 2001 and included regions of both intensive and less intensive pea cultivation. The occurrence of pea moth adults in the fields was assessed with pheromone traps, and the percentage of damaged pods and pea seeds in each field was determined. The number of pea moths in pheromone traps and the percentage of damaged seeds increased linearly when the area under pea cropping during the previous year (within a 4-km distance) increased, and decreased exponentially when the distance to the nearest pea field in the previous year increased. Furthermore, the percentage of damaged pods and seeds was higher in organic than in conventional fields. Expansion of pea cropping would change the spatial distribution of pea fields, thus affecting the risk of pea moth infestation. An increase in the scale and frequency of pea cropping increases the need for plant protection.