UC Riverside

This study addresses the need for improved management of insect-transmitted viruses in muskmelons in the Southwestern U.S., a region responsible for approximately 80% of domestic production. Current management via repeated insecticide applications to manage vectors is only marginally effective and not sustainable due to insecticide resistance, changing product registrations, and environmental impacts. As an alternative, we evaluated two plant immunity elicitors for efficacy in activating virus resistance in cantaloupe: acibenzolar-S-methyl (ASM) (Actigard®) and an extract of Reynoutria sachalinensis (Regalia®). Each was evaluated in the context of three different insecticide regimes for managing virus vectors. All trials were conducted over multiple years in two melon production regions with different virus and vector threats. In each trial, we monitored plant growth, disease incidence and type, yield, and fruit quality. ASM and Reynoutria reduced the incidence of zucchini yellow mosaic virus (ZYMV) symptoms and improved the yield and fruit quality of plants challenged with ZYMV under conditions typical of the Central Valley, CA growing region. While disease attenuation from elicitor use was observed in both trials with ZYMV as the challenge pathogen, improvements in yield and fruit quality were only evident in one trial. In contrast to results with ZYMV, elicitors were not effective in attenuating infections by whitefly-transmitted criniviruses in the low desert region. Instead, we only observed improvements in plant vigor and yield from using grower standard insecticides. Our experiments document both promising effects and important limitations of elicitor products for virus control in muskmelons grown in the Southwestern U.S.