The status of citrus IPM in California

Citrus is grown in 4 distinct regions of California and differences in the climates in these regions influence the citrus varieties, pests and natural enemies that occur. The heaviest insecticide treatments occur in the San Joaquin Valley where extremes of heat and cold reduce the efficacy of natural enemies. In the San Joaquin Valley, citrus thrips Scirtothrips citri (Moulton) and California red scale Aonidiella aurantii (Maskell) have been primary pests for many decades. Forktailed bush katydid Scudderia furcate Brunner von Wattenwyl and citricola scale Coccus pseudomagnoliarum (Kuwana) became primary pests when selective insecticides replaced organophosphate and carbamate insecticides. San Joaquin Valley growers maintain their integrated pest management (IPM) program by utilizing low rates of pyrethroids or organophosphate insecticides for katydids and applying organophosphates for citricola scale in alternate years – resulting in an average of 3-4 treatments for all pests per year. In 2008, the Asian citrus psyllid, Diaphorina citri Kuwayama was discovered and in 2012 huanglongbing disease was found in California. While the majority of find sites of the psyllid have been in residential areas of the state, it is expected that the pest and disease will become established in commercial citrus in the near future. Because the disease is difficult to detect when trees first become infected and there is no cure for the disease, psyllid population reduction in combination with infected tree removal is currently the most effective strategy for preventing disease spread. Because the most effective treatments for Asian citrus psyllid are broad spectrum in nature, California citrus IPM will experience major disruptions in the near future. There will be regional differences in the risk of pest and disease establishment and in the impact of treatments on the IPM program.