Potential factors contributing to the decline of Iris Yellow Spot Virus in organically grown onion crops in Canterbury and Hawke’s Bay over three years
The Tospovirus Iris yellow spot virus (IYSV), transmitted by thrips (predominantly Thrips tabaci), was first recorded in New Zealand in 2007. In March 2015, symptoms of the virus were relatively widespread in an organically managed onion crop in Canterbury. Onion plants were sampled for the presence of T. tabaci adults and larvae and for IYSV symptoms on an organically managed farm in Canterbury in 2014–2015, 2015–16 and 2016–17, and on a similar farm in Hawke’s Bay in 2014–2015 and 2015–16. An immunoassay was used to confirm the presence of IYSV in some symptomatic plants. In Canterbury, IYSV symptoms were less apparent in 2015–16 and no symptoms were observed in 2016–17. No IYSV symptoms were observed in the Hawke’s Bay onion crop, despite relatively high T. tabaci numbers. The virus symptoms declined from when they were first observed in March 2015 to undetectable levels in 2016–17 in Canterbury, which may be attributed to crop location, fewer thrips and the absence of a disease reservoir in volunteer Allium cepa plants or other hosts.
Bag S, Schwartz HF, Cramer CS, Havey MJ, Pappu HR 2015. Iris yellow spot virus (Tospovirus: Bunyaviridae): from obscurity to research priority. Molecular Plant Pathology 16: 224-237.
Gent DH, Schwartz HF, Khosla R 2004. Distribution and incidence of Iris yellow spot virus in Colorado and its relation to onion plant population and yield. Plant Disease 88: 446-452.
Gent DH, du Toit LJ, Fichtner SF, Mohan SK, Pappu HR, Schwartz HF 2006. Iris yellow spot virus: An emerging threat to onion bulb and seed production. Plant Disease 90: 1468-1480.
Jeong Jj, Noh HjJ 2014. A review of detection methods for the plant viruses. Research in Plant Disease 20: 173-181.
Larentzaki E, Shelton AM, Musser FR, Nault BA, Plate J 2007. Overwintering locations and hosts for onion thrips (Thysanoptera: Thripidae) in the onion cropping ecosystem in New York. Journal of Economic Entomology 100: 1194-1200.
Martin NA 2015. Onion thrips, Thrips tabaci (Thysanoptera: Thripidae), overwintering in South Auckland, New Zealand: the importance of the local bionomic data/temperature model and biosecurity implications. New Zealand Entomologist 38: 17-27.
Moritz G, Kumm S, Mound LA 2004. Tospovirus transmission depends on thrips ontogeny. Virus Research 100: 143-149.
Nielsen MC, Fletcher CD, Teulon DAJ 2004. Monitoring thrips flight with 7.5 metre high suction traps (Poster abstract). New Zealand Plant Protection 57: 339.
Popay I, Champion P, James T 2010. An Illustrated Guide to Common Weeds of New Zealand. 3rd ed. Christchurch, New Zealand, New Zealand Plant Protection Society (Inc.).
Smith TN, Wylie SJ, Coutts BA, Jones RAC 2006. Localized distribution of Iris yellow spot virus within leeks and its reliable large-scale detection. Plant Disease 90: 729-733.
Smith EA, Ditommaso A, Fuchs M, Shelton AM, Nault BA 2011. Weed hosts for onion thrips (Thysanoptera: Thripidae) and their potential role in the epidemiology of Iris yellow spot virus in an onion ecosystem. Environmental Entomology 40: 194-203.
Smith EA, Fuchs M, Shields EJ, Nault BA 2015. Long-distance dispersal potential for onion thrips (Thysanoptera: Thripidae) and Iris yellow spot virus (Bunyaviridae: Tospovirus) in an onion ecosystem. Environmental Entomology 44: 921-930.
Srinivasan R, Sundaraj S, Pappu HR, Diffie S, Riley DG, Gitaitis RD 2012. Transmission of Iris yellow spot virus by Frankliniella fusca and Thrips tabaci (Thysanoptera: Thripidae). Journal of Economic Entomology 105: 40-47.
Ward LI, Perez-Egusquiza Z, Fletcher JD, Ochoa Corona FM, Tang JZ, Liefting LW, Martin EJ, Quinn BD, Pappu HR, Clover GRG 2009. First report of Iris yellow spot virus on Allium cepa in New Zealand. Plant Pathology 58: 406-406.