North American Grapevine Yellows: Knowns, unknowns and research objectives. Tony Wolf & Tremain Hatch Winter 2012

Transcription

1 North American Grapevine Yellows: Knowns, unknowns and research objectives Tony Wolf & Tremain Hatch Winter 2012

2 North American Grapevine Yellows

3 Aborted fruit

4 Leaf sympoms

5 Rubbery shoots

6 Rubbery shoots

7 combination of these three symptoms

8 Nomenclature of grapevine yellows diseases North American grapevine yellows Flavescence dorée Bois noir Australian grapevine yellows Others as well

9 Yellows diseases are caused by phytoplasmas Limited to phloem (food-conducting) tissues of plant some symptoms may reflect a blockage of phloem sieve tubes Bacteria-like organisms; fairly small genome

10 Examples of Yellows diseases: wide host range, global distribution Disease common name 16S rdna group-subgroup Named 'Candidatus Phytoplasma' species Aster yellows (AY) 16SrI 'Candidatus Phytoplasma asteris' Western X-disease Palm lethal yellowing 16SrIII-A 16SrIV-A Elm yellows 16SrV-A 'Ca. Phytoplasma ulmi' Flavescence dorée 16SrV-C Clover proliferation 16SrVI-A 'Ca. Phytoplasma trifolii' Apple proliferation 16SrX-A 'Ca. Phytoplasma mali' Pear decline 16SrX-C 'Ca. Phytoplasma pyri' European stone fruit Y 16SrX-F 'Ca. Phytoplasma prunorum' Stolbur phytoplasma 16SrXII-A Australian GY 16SrXII-B 'Ca. Phytoplasma australiense'

11 A brief history of North American Grapevine Yellows Leaf Curl and Berry Shrivel, DeChaunac, New York State (Uyemoto, 1975 Uyemoto et a., 1977) FD-like symptoms in Riesling, New York State (Pearson et al., 1985) Scaphoideus titanus abundant in New York State GY vineyards, and these insects often show + reaction to FD antibodies in ELISA (Maixner et al., 1993). Yellows, or North American Grapevine Yellows reported in Virginia (Prince et al., 1993; Wolf et al., 1994).

12 A brief history. continued Yellows, or North American Grapevine Yellows reported in Virginia (Prince et al., 1993; Wolf et al., 1994): Initial findings related the Virginia phytoplasma to Xdisease (16SrIII group) Subsequently (Prince et al., 1994), a second phytoplasma was detected in the 16SrI group (Aster Yellows) Both phytoplasmas found in cultivated vines (e.g., Chardonnay) and in asymptomatic wild vines (Vitis spp.), and the AY type was also detected in black cherry (Prunus serotina)

13 A brief history. continued NAGY sub-group findings (Davis et al., 1998) X-disease (16SrIII group) phytoplasma unique for this taxonomic group and given I sub-group classification Aster yellows (16SrI group) also unique, and given A sub-group classification

14 A brief history. fast-forward Reassessment of NAGY phytoplasmas from eastern US vineyards (Davis et al. 2012) confirmed only 2 phytoplasmas in vineyards of VA, MD, PA and NY. As originally stated, these phytoplasmas are not the cause of the European yellows diseases such as Flavescence dorée or Bois noir Dr. Robert Davis USDA/ARS Beltsville, MD

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16 Overview of NAGY development

17 Phytoplasma-positive plants Red and white clover wild grapevine dandelion aster American elm sycamore black cherry

18 Vectors of Other Phytoplasma Diseases Leafhoppers Planthoppers Psyllids

19 Identification of vectors Dr. LeAnn Beanland Virginia Tech Malaise trap

20 Plant disease vectors found in samples *Scaphoideus titanus

21 Mean # S. titanus at BRC Mean # S. titanus at GM Predicted No. of S. titanus at Brown Seasonal increase of Scaphoideus titanus Forest Vineyard Collection Day Forest Vineyard Collection Day Forest Vineyard Collection Day

22 Total # Scaphoideus titanus transect sticky traps over a two-year period

23 Example of edge effect of NAGY incidence at a small vineyard near Flint Hill, VA. Each black spot is an affected vine observed in one year (1997). Pasture Chardonnay (1.15 ha) Riesling (1.17 ha) Pasture N Sauvignon blanc (< 0.2 ha) Pasture

24 Examples of leafhoppers (Scaphoideus titanus and Jikradia olitorius) that showed a pronounced difference in yellow sticky trap captures between woodland and vineyard locations. Poles # 3,4,7,8 Trap location on pole S. titanus J. olitorius Vineyard Canopy (5 ) 1 10 Vineyard Lower (8 ) 1 1 Vineyard Middle (14 ) 1 0 Vineyard Upper (20 ) 0 0 Poles # 1,2,5,6 Woods Canopy (5 ) Woods Lower (8 ) Woods Middle (14 ) 7 36 Woods Upper (20 ) 9 19

25 Candidate Vector Species Captured in Sweep Samples Agallia constricta 2960 Polyamia weedi 336 Exitianus exitosus 334 Latalus sayi 311 Amblysellus curtisii 234 Deltocephalus flavicosta 189 Endria inimica 167 Sorhoanus orientalis 161 Chlorotettix galbanatus 122 Graminella nigrifrons 85 Paraphlepsius irroratus 64 Balclutha abdominalis 54 Macrosteles quadrilineatus 26 Doratura stylata 22 Jikradia olitorius 15 Osbornellus auronitens 13 Scaphytopius nigrifrons 12 Agalliopsis novella 8 Athysanus argentarius 8 Acertagallia sp. 4 Scaphoideus titanus 3 Aphrodes flavostrigatus 2 Colladonus clitellaris 2 Idiodonus kennicotti 1

26 4/2/2002 4/16/2002 4/30/2002 5/14/2002 5/28/2002 6/11/2002 6/25/2002 7/9/2002 7/23/2002 8/6/2002 8/20/2002 9/3/2002 9/17/ /1/ /15/2002 Mean # A. constricta captured in the vineyard 4/2/2002 4/16/2002 4/30/2002 5/14/2002 5/28/2002 6/11/2002 6/25/2002 7/9/2002 7/23/2002 8/6/2002 8/20/2002 9/3/2002 9/17/ /1/ /15/2002 Mean # A. constricta captured in scrub Agallia constricta Captured in Sweep Samples Date Date

27 Species that have Tested Positive (PCR) for Phytoplasmas Agallia constricta Balclutha abdominalis Latalus sayi Graminella nigrifrons Scaphytopius sp. Draeculacephala sp. Endria inimica Amblysellus curtisii Exitianus exitiosus Paraphlepsius irroratus Jikradia olitorius Deltocephalus flavicosta

28 Transmission Experiments Required to show that insect is truly a vector

29 Insects Caged on GY-infected Grapevine in the Vineyard

30 Rearing Insect-free Plants

31 Several positive transmission vectors of NAGY Agallia constricta Scaphoideus titanus Macrosteles spp.

32 Lespedeza sp.

33 Examples of non-vitis plant hosts that were found to harbor NAGY phytoplasmas Species Common name + / total Phyto. group Prunus serotina Black cherry 1 / 9 AY Platanus occidentalis Sycamore 1 / 2 X Ulmus sp. Elm 1 / 3 AY Trifolium pratense Red clover 2 / 2 1 AY, 1? Trifolium repens White clover 2 / 2 1 AY, 1? Lespedeza sp. Lespedeza 1 / 1 AY

34 What we know: Grapevine yellows in Virginia is caused by at least 2 distinct phytoplasmas Multiple insect (leafhopper) vectors are involved These insects are typically more abundant outside the vineyard than within Multiple alternative hosts are implicated Grapevine varieties vary in susceptibility to NAGY Nurseries probably not a source of infected vines (although this was recently of concern in Canada)

35 What we don t know: Are all candidate vectors equally effective (or can we target specific one(s)? Would persistent (e.g., soil-applied) insecticides effectively reduce transmission rates? Multiple alternative hosts are implicated -- but which are most common to high incidence vineyards? Is removal truly effective in reducing phytoplasma reservoir?

36 What we don t know (continued): What strategies can be used to suppress spread? o Site selection o Variety selection o Removal of potential alternative hosts What tactics can be used to suppress spread? o Insecticides o Landscape management o Removal of affect vine (or vine parts)

37 Our work with NAGY has been dormant since 2006 We just filled a position to explore some aspects of NAGY, including: o What are the common landscape features that distinguish high risk vineyards What tactics can be used to suppress spread? o Targeted insecticide applications o Landscape and/or vineyard floor management o Removal of affect vine (or vine parts) This will require a multi-year approach. Unfortunately, there are no guarantees of success with this work

38 Thank you. Questions?