|Silva, Jose - Agronomical Institute Of Campinas (IAC)|
|Andrade, Moacir - Universidad De Sao Paulo|
|Maldonado, Jr, Walter - Sao Paulo State University (UNESP)|
|Andrade, Eduardo - Embrapa|
|Machado, Marcos - Agronomical Institute Of Campinas (IAC)|
Submitted to: Crop Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/12/2016
Publication Date: 2/24/2016
Citation: Silva, J.A., Hall, D.G., Gottwald, T.R., Andrade, M.S., Maldonado, Jr, W., Alessandro, R.T., Lapointe, S.L., Andrade, E.C., Machado, M.A. 2016. Repellency of Psidium guajava cultivars to the Asian citrus psyllid, Diaphorina citri. Crop Protection. 84:14-20.
Interpretive Summary: Asiatic huanglongbing (also known as citrus greening disease) is the most devastating disease of citrus worldwide. It is caused by a bacterium transmitted by the Asian citrus psyllid. With respect to psyllid control, of interest is that reports in the literature indicate guava can be repellent to Asian citrus psyllid (ACP). We conducted research to further evaluate repellency of guava. All guava materials we tested had at least some repellency to the psyllid. Mature guava leaves tended to have a greater repellent effect than young guava flush. Each of five guava oils exhibited repellency. Identification of the constituents responsible for repellency could lead to new psyllid management tactics.
Technical Abstract: Asiatic huanglongbing (HLB)(also known as citrus greening disease) is the most devastating disease of citrus worldwide. It is caused by a bacterium ‘Candidatus Liberibacter asiaticus’ and transmitted by the Asian citrus psyllid (ACP), Diaphorina citri. Considerable research has been conducted toward developing and implementing HLB and ACP management strategies. With respect to ACP control, of interest is that reports indicate guava, Psidium guajava, can be repellent to ACP. We conducted research to further evaluate repellency of guava to ACP. In one set of experiments, guava oil from five Brazilian guava cultivars (‘J3’, ‘Pedro Sato’, ‘Século XXI’, ‘Thailand’ and ‘Paluma’) was extracted from leaves (mature and immature) by hydro-distillation in a Clevenger apparatus and evaluated for psyllid repellency. In a second set of experiments, repellency of guava leaves to ACP was investigated using leaves (young flush leaves and mature leaves) from two guava cultivars, ‘Pink’ and ‘Thai White’. In each set of experiments, repellency was evaluated by releasing ACP adults into a cage with two large vials, one containing a young flush shoot of Murraya exotica (a favored host plant of the psyllid, the flush of which is highly attractive to ACP) and one with M. exotica flush and the test material of interest (guava oil, mature guava leaf or guava flush). The adults were free to move throughout the cage and into the vials, and the number of psyllids in each vial was counted after 24 hours. The results showed that all guava materials tested had at least some repellency to ACP. Mature guava leaves tended to have a greater repellent effect than young guava flush. Each of the five oils exhibited repellency. A report in the literature suggested that sulfur compounds associated with guava may be responsible for ACP repellency. Interestingly, the five guava oil extracts we studied were repellent to ACP but none contained any sulfur compounds. Identification of the constituents responsible for repellency could lead to new ACP management tactics.