Insect-transmitted viruses and their Management in vegetables Rajagopalbabu Srinivasan Bhabesh Dutta Tim Coolong UGA PIs UGA PIs UGA PIs In this webinar.. § Introduction to vectors, viruses, transmission § Insect-transmitted viruses in tomato and squash § OREI trials Prominence of insect-borne viruses Bacteria, fungi, and phytoplasmas 70% Viruses & viroids transmitted by vectors - Power, A. G. 2000. Current Opinion in Plant Biology 3: 336-340. - Hohn, T. 2007. PNAS 17905-17906. Insects as vectors of phytoviruses 400 80000 Total species described vector species viruses transmitted 300 60000 40000 200 20000 100 0 0 Homoptera Coleoptera Thysanoptera Homoptera Coleoptera Thysanoptera Thrips Larvae § Sucking mouthparts § Epidermal punctures Frankliniella fusca Pupae Adults PP virus transmission - Nagata and Peters. 2001. Virus-Insect-Plant- Interactions, pp 51-67, AP. - Whitfield et al. 2005. Annu. Rev. Phytopathol. 43:459–89. -Thrips photographs by G. Mortiz Thrips-transmitted tomato spotted wilt orthotospovirus in tomato Bemisia tabaci cryptic species - de Moya et al. 2019. Diversity Piercing and sucking mode of feeding § Key to transmission- secrete two types of saliva (watery saliva & gelling saliva) - Dixon 1973 Virus transmission Kliot et al. 2013 Viruses. 5(6):1516-35 Semi-persistent transmission Persistent circulative transmission Tomato yellow leaf curl virus (TYLCV) • DNA virus • Genus Begomovirus, Family Geminiviridae Marchant -unpublished Tomato chlorosis virus (ToCV) • RNA virus • Genus Crinivirus, Family Closteroviridae Squash vein yellowing virus (SqVYV) - Adkins et al. Plant Dis. 92:1119-1123 § RNA virus § Genus Ipomovirus, Family Potyviridae Cucurbit yellow stunting disorder virus (CYSDV) § RNA virus § Genus Crinivirus, Family Closteroviridae Cucurbit leaf crumple virus (CuLCrV) § DNA virus § Genus Begomovirus, Family Geminiviridae Pathosystem: Essentially a virus web Mixed infections (CYSDV + CuLCrV) § Double infection in all samples § Symptom severity OREI pertinent research § Tomato and squash viruses § Thrips trials-spring; squash trials- fall § Biological control with phytoseiid mite § Challenges with biological control: very low threshold & minimal management window Amblyseius swirskii feeding on adult chilli thrips. Photograph by Steven Arthurs, University of Florida Thrips-TSWV tomato trial Number Mite treatment Variety 1 Control Rosso Sicilian 2 Predatory mite release at base of the plant Rosso Sicilian 3 Predatory mite release on foliage Rosso Sicilian 4 Predatory mite sachets Rosso Sicilian 5 Control SV7631TD 6 Predatory mite release at base of the plant SV7631TD 7 Predatory mite release on foliage SV7631TD 8 Predatory mite sachets SV7631TD Thrips-TSWV tomato trial § Two releases. At planting and 3 to 4 weeks post planting Thrips-TSWV tomato trial Thrips-TSWV tomato trial § TSWV only observed in susceptible cultivars Rosso Sicilian § TSWV incidence <15% Tomatoes with & without TSWV resistance. Photos- David Riley, UGA Thrips-TSWV tomato trial Tomatoes with & without TSWV resistance. Photos- David Riley, UGA Thrips-TSWV tomato trial Tomatoes with & without TSWV resistance. Photos- David Riley, UGA Whiteflies-TYLCV tomato trial Whiteflies-TYLCV tomato trial Whiteflies-TYLCV tomato trial § Severe TYLCV incidence ~100% infection Integrating management options § Host resistance § Cultural options § Chemical options Whiteflies-CuLCrV & CYSDV squash trial Whiteflies-CuLCrV & CYSDV squash trial Whiteflies-CuLCrV & CYSDV squash trial Whiteflies-CuLCrV & CYSDV squash trial § Severe CuLCrV and/or CYSDV incidence ~100% infection Whiteflies-CuLCrV & CYSDV squash trial 2020 400 350 300 250 200 Adult Whiteflies 150 100 50 0 control base foliage sachet Mite Treatment Whiteflies-CuLCrV & CYSDV management in squash - conventional Integrating management options § Cultural tactics, mulch, and insecticides Integrating management options § Cultural tactics + chemical tactics Options for organic production to manage insect-transmitted viruses § Integration with cultural and/or chemical tactics § Exclusion § Biological control § Future trials Acknowledgements.