Screening organic pesticides for control of Asian citrus psyllid (Diaphorina citri) in California

The Asian citrus psyllid (Diaphorina citri Kuwayama) is a serious citrus pest, as it transmits the incurable greening disease, also called Huanglongbing (HLB), which has had a devastating effect on the citrus industry throughout the world. HLB was detected in Los Angeles, California, in 2012. Therefore, we began an intensive screening of conventional and organic insecticides, against the Asian citrus psyllid (ACP), in Southern California. This article reports the results on the efficacy of several organic insecticides with different modes of action on the control of ACP. The trials were conducted from 2012 to 2014 at the greenhouse of the Chula Vista insectary using plants of ‘Volkameriana’ lemon that were infested with ACP adults prior to treatment application. Products evaluated included botanical, biological and horticultural oils, used for organic plant production (i.e., pyrethrins, azadirachtin, diatomaceous earth, kaolin), and several adjuvants. All trials included a water treated control and Danitol, a pyrethroid conventional insecticide, which was used as a positive control to ensure mortality. Forty eight hours after treatment, Danitol always caused 100 % mortality. Many of the organic products tested and the adjuvants were also effective on contact, causing from 80 to 90 % mortality at this time. Danitol, had a residual effect of at least one month, causing up to 98 % of adult mortality 33 days after treatment. In contrast, the efficacy of organic compounds fell rapidly over time. Most products caused less than 60 % mortality fourteen days after treatment. Our results suggested that repeated applications of organic products would be necessary to sustain a high level of control.