Evaluation of sulfur based plant volatiles as possible repellents for Asian citrus psyllid, Diaphorina citri (Hemiptera: Psyllidae)

Asian citrus psyllid (ACP), Diaphorina citri Kuwayama, vectors the causal bacteria of the devastating citrus disease, huanglongbing (HLB). Dimethyl disulfide (DMDS) was recently identified as a metabolite produced in large amounts by wounded guava leaves. We conducted a series of behavioral investigations of D. citri’s response to citrus volatiles with and without guava leaf volatiles and to synthetic dimethyl disulfide (DMDS), in laboratory olfactometers and in the field. Volatiles from guava leaves significantly inhibited D. citri’s response to normally attractive host-plant (citrus) volatiles. A similar level of inhibition was recorded when synthetic DMDS was co-released with volatiles from citrus leaves. In addition, the volatile mixture emanating from a combination of intact citrus and intact guava leaves induced a knock-down effect on adult D. citri. Compounds similar to DMDS including did not affect the behavioral response of D. citri to attractive citrus host plant volatiles in laboratory olfactometer assays. In a small plot field experiment, populations of D. citri were significantly reduced by deployment of synthetic DMDS from polyethylene vials compared with untreated control plots. Subsequent studies have focused on determining whether mixtures of sulfur based compounds exhibit greater behavioral activity on D. citri than individual compounds. The results of the current study verify that guava leaf volatiles inhibit the response of D. citri to citrus host plant volatiles and suggest that the induced compound, DMDS, is responsible for this effect. Also, we provide direct field evidence that deployment of DMDS reduces densities of D. citri and thus may have potential as a novel control strategy for this plant disease vector.