04006naa a2200229 a 450000100080000000500110000800800410001910000230006024501950008326000090027852031410028765000320342865000310346065000170349170000170350870000190352570000190354470000150356370000170357870000190359577301620361411326242022-10-18       2022    bl uuuu     u00u1 u    #d1 aSILVA, M. C. C. R.  aInfectivity of corn leafhopper, Dalbulus maidis (HemipterabCicadellidae), with Maize bushy stunt phytoplasma and Spiroplasma kunkelii in Santa Catarina State, Brazil.h[electronic resource]  c2022  aGreat amount of white-pale insect of no more than 0.5 cm flying off corn plants has been observed by maize producers in Santa Catarina State (SC), Brazil. In fact, it was registered a great loss in 2020/21 year-crop due to corn stunt disease complex incidence, which is caused by two mollicutes, the Maize bushy stunt phytoplasma (MBSP, ?Candidatus Phytoplasma asteris?, 16SrI-B), the corn stunt spiroplasma (Spiroplasma kunkelii Whitcomb), and the virus (Mayze rayado fino virus), all pathogens transmitted by the corn leafhopper, Dalbulus maidis (DeLong & Wolcott) (Hemiptera: Cicadellidae). We intended to verify the natural infectivity of D. maidis with both mollicutes during the maize first crop in 2021/22 year-crop. In this sense, we installed yellow sticky traps in 22 corn crops of different municipalities in SC (14 crops in the West region, 3 crops in the North region, 2 crops in Serrana regions, 2 crops in Itaja?? Valley and 1 crop in South region). The traps were weekly replaced during 27 weeks (from July, 2021 to January 2022) and immediately addressed to the laboratory for molecular diagnostics. If there were up to 3 insects captured by the traps, we performed the diagnosis of all of them individually; if more than 3 insects, we performed diagnosis in triplicates until 7 samples. After a CTAB DNA extraction of those insect samples, a multiplex PCR was performed using primers R16F2/R16R2 and CSSF2/CSSR6 for MBSP and S. kunkelii detection, respectively. We analyzed 1571 samples. We obtained 161 positives samples for MBSP (10.24%) and 254 positives samples for S. kunkelii (16.16%). In spite of finding some corn leafhoppers in the early weeks of the assay, we started to get positive-PCR for both Mollicutes from the 4th week on, when corn crops have all already been sown. Corn crops in Itapiranga and Palmitos, both in the West region, presented the highest number of week events of MBSP-positive samples, respectively, 44.4% and 50%, whereas corn crops in Caxamb?? do Sul, Uni??o do Oeste, Chapec??, S??o Miguel do Oeste (all located in the West region) and Ituporanga (Itaja?? Valley) presented, 47.8 to 55.6% of S. kunkelli-positive events. The 4th and the 22nd were critical for MBSP detection, in which we got 83.3% and 100% of positive samples for MBSP. Several weeks were important for S. kunkelli, as we found more positive-events at 4, 6 and 7 weeks after the beginning of monitoring (more than 80% of positive events) and from 22nd week on after traps installation (more than 65%). In this sense, there was more D. maidis infectivity with S. kunkelii along the first planting and both mollicutes were detected in the leafhoppers when maize was already sown. The crops located in the West region showed more insect-infectivity with both pathogens. We noticed a fluctuation of insect-infectivity through the weeks. A crop season surveillance such as we performed shall help to determine the best time-points and locations for D. maidis infectivity assessment with MBSP and S. kunkelii to establish an efficient and achievable monitoring program and risk analysis for the corn stunt disease complex.  acorn leafhopper infectivity  acorn stunt disease complex  aepidemiology1 aFERREIRA, J.1 aGORAYEB, E. S.1 aSAVARIS, D. M.1 aBORGES, V.1 aSILVA, F. N.1 aRIBEIRO, L. P.  tIn: WORKSHOP BRASILEIRO DE EPIDEMIOLOGIA DE DOEN??AS DE PLANTAS, 6., 2022, Chapec??. Resumos... Bras??lia: Sociedade Brasileira de Fitopatologia, 2022. p. 42