San Jose scale infestations in cherry are becoming more prevalent in the northern San Joaquin Valley. Some infestations were severe enough to kill trees within one or two years. In addition to tree and limb death, scale feeding damages the fruit surface, making them unmarketable, especially for export. Previous research identified an abundance of parasitic wasps, which may reduce San Jose scale numbers. In 2008, spotted-wing drosophila became a pest throughout California and changed pest management practices in cherry.
Area IPM Advisor Jhalendra Rijal suggests that the management practices for spotted-wing drosophila may harm parasitic wasps and reduce their numbers. To determine if this is true, Rijal assessed the occurrence and abundance of San Jose scale parasites in orchards using sticky traps baited with the San Jose scale pheromone. He observed two parasites, Aphytis spp. and Encarsia spp., in all orchards. Low parasite numbers in May coincided with spotted wing drosophila insecticide applications. Rijal plans to continue monitoring San Jose scale and its parasites.
This research improves our knowledge of the San Jose scale phenology in the northern San Joaquin Valley. It is anticipated that if crawler treatments are needed, a better understanding of the phenology can lead to improved application timing so that crawler treatments are effective and do not interfere with cherry harvest. Rijal’s work will also enhance our understanding of how broad-spectrum insecticide applications for spotted-wing drosophila affect parasites in cherry orchards.
Long-Term Impacts
