Insect-transmitted 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 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

Larvae § Sucking mouthparts § Epidermal punctures Frankliniella fusca

Pupae

Adults PP 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 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 , Family

Marchant -unpublished Tomato chlorosis virus (ToCV)

• RNA virus • Genus , Family Squash vein yellowing virus (SqVYV)

- Adkins et al. Plant Dis. 92:1119-1123 § RNA virus § Genus , Family 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