Evaluating the Efficacy of the Systems Approach at Mitigating Five Common Pests in Oregon Nurseries

Abstract

In Oregon, the U.S. Nursery Certification (USNCP), Grower Assisted Inspection (GAIP), and Shipping Point Inspection (SPI) programs are used to certify nursery plants as pest free. To compare the programs' effectiveness for mitigating pest risk, potted plants grown within two USNCP, two GAIP, and two SPI nurseries were surveyed for Phytophthora root rot (Phytophthora spp.), Phytophthora foliar blight (Phytophthora spp.), bittercress (Cardamine spp.), snails and slugs (Class Gastropoda), and root weevils (Otiorhynchus spp.). A total of 1,635 plots were surveyed in the nurseries, with one or more pests detected in 1,003 plots. Based on the total percentage of plots found infested with a pest, significantly fewer were detected in the GAIP nurseries (55%) than in the USNCP nurseries (68%). However, bittercress incidence was significantly higher in GAIP nurseries (21%), while snails and slugs incidence was significantly higher in USNCP nurseries (49%), and Phytophthora root rot incidence was significantly higher in SPI nurseries (31%). Also, the plant families grown by the nurseries had a significant impact on pest incidence for two of the target pests, Phytophthora root rot and root weevils. While the GAIP seemed the best at mitigating pest incidence overall, none of the certification programs was consistently the most effective against all five target pests.