Evaluation of N analysis to trace the origin of (Hemiptera: Liviidae) to citrus orchard fertilization management.

We investigated the variability of nitrogen stable isotope ratios N/N (expressed as δN) on citrus orchards with different fertilization management practices (organic versus conventional) and its correlation with the δN values of the key citrus pest Kuwayama (Hemiptera: Liviidae) feeding on such plant material. Tracing the origin of this pest in open field is crucial since the insect is a vector of the incurable and devastating citrus disease known as Huanglongbing. We hypothesized that the origin (natal tree) of the pest may be deduced by correlating the δN values obtained from the young citrus leaves and from adults of raised on them. First, laboratory experiments were performed to understand the acquisition and incorportation of the δN values by . Second, we confirmed the positive correlation between the δN values of the young citrus leaves and . Finally, field sampling was carried out in 21 citrus orchards from Southern California to study the variability on the δN values on organic and conventional commercial citrus orchards. Laboratory results suggest that the analyses of the δN values can be regarded as a useful method to trace the origin of the pest. However, the high variability in nitrogen resource used in both fertilization management practices (especially in organic orchards) by growers makes the application of this technique unfeasible to pinpoint the origin of in the citrus agroecosystem.