Survey of the citrus leprosis vector (Brevipalpus yothersi) and phytoseiids in spontaneous plants of an organic citrus orchard.

Citrus leprosis (CL) is one of the most important viral diseases in sweet orange orchards in Latin America. It is caused by members of at least five species of the so-called Brevipalpus-transmitted viruses (BTV), and the prevalent is Citrus leprosis virus C (CiLV-C). This virus has the broadest host range amongst all CL-associated viruses and is transmitted by Brevipalpus yothersi, a polyphagous mite that can colonize a large variety of host plants, including some spontaneous ground cover plants. But if, on one hand, spontaneous plants can host CL virus and vector, on the other hand, they can offer alternative food for predators, equally common in organic citrus orchards. Brevipalpus yothersi and predator mites were surveyed in 33 spontaneous plants of a Westin sweet orange orchard conducted under organic production system in Brazil, from June 2010 to April 2011. Predatory mites were identified as phytoseiids, and Iphiseiodes zuluagai was the prevalent species, representing 58% of all predators. Other phytoseiids were considered accidental species in the area. Ageratum conyzoides and Alternanthera tenella were the most represented plant host species to predators, comprising 28 and 10% of the total surveyed plants, respectively. Brevipalpus yothersi specimens were detected on various spontaneous species: A. conyzoides, A. tenella, Amaranthus deflexus, Bidens pilosa, Ipomoea quamoclit, I. cairica, Merremia cissoides, Solanum americanum, Panicum maximum, and, predominantly, Commelina benghalensis. The latter has been previously reported as host of CiLV-C as well and, therefore, it is recommended to eliminate this species from citrus orchards.

Brevipalpus Species Vectoring Citrus Leprosis Virus (Cilevirus and Dichorhavirus).

Citrus leprosis (CL) is one of the most devastating viral diseases of orchards, and industries correspondingly invest highly in the management and control of the virus vector. In Brazil, the disease is caused most predominantly by the citrus leprosis virus C (CiLV-C, Kitaviridae: Cilevirus), and also by citrus leprosis virus N (CiLV-N, Rhabdoviridae: Dichorhavirus). Both viruses are transmitted by false spider mites and at least three different species, Brevipalpus yothersi Baker, B. papayensis Baker, and B. phoenicis (Geijskes) sensu stricto, have been reported in citrus orchards. The main goal of this study was to evaluate the capacity of three Brevipalpus species to transmit citrus leprosis virus (cytoplasmic and nuclear types). The capacity of false spider mites to acquire the virus was accomplished using RT-PCR and the ability to inoculation the virus to host plants (common bean and sweet orange) was assessed via viral transmission assays. Common beans infested with B. yothersi and B. papayensis showed symptoms of CiLV-C in 87.5 and 17% of the plants assessed, respectively. In sweet orange, B. yothersi was exclusively able to inoculate CiLV-C, and around 83% of samples were symptomatic. Host plants infected with CiLV-N showed symptoms only when infested with B. phoenicis sensu stricto (s.s.). All the Brevipalpus species (Acari: Tenuipalpidae) were able to acquire both viruses (CiLV-C and CiLV-N), but not infect plants. These results suggest the existence of virus-vector specificity in the leprosis pathosystem, and this information will be critical for enhancing our further understanding of epidemiological features and disease management.