Update on potato psyllids and zebra chip in – Dec 2015

Erik J. Wenninger Associate Professor of Entomology Kimberly Research & Extension Center Zebra chip (ZC) disease

• Disease caused by bacterium (Candidatus solanacearum [Lso]) • Bacterium vectored by the potato psyllid (Bactericera cockerelli)

1st instar nymph

(5 nymphal instars) close-up of egg late instar nymph

adult and eggs • 1 generation = 2-3 wks • 77-86 F = optimum temp

adult (2-3 mm long) Clear wings

White markings on head

White band on abdomen Potato psyllid nymphs

Whitefly nymph A brief history of ZC

• 1994 – • 2000 – • 2000… – Southern regions and CA • 2008 – bacterium identified • 2011 – PNW • (Also present in and C. America) A brief history of ZC in Idaho Monitoring program expanded ZC in ID; ca. 1% incidence; mostly Magic Valley ZC incidence nil ZC incidence nil

2011 2012 2013 2014 2015

monitoring began; ca. 1% incidence, some 3-15+%; mostly Magic Valley Magic Valley • 10 sticky traps per field arranged around perimeter

• 5-minute vacuum 1 sample along 10 windward edge 2

3 9

8 4

5 7 • 10 leaf samples 6 from each sticky card station (100 leaves per field) 2012-2015 Monitoring programs • “Intense” program • “Light” program – 13 fields – 71-94 fields – Weekly sampling – Weekly sampling – 10 sticky traps per field – 4 sticky traps per field – Vacuum samples 1 1

10 2

– Leaf samples 9 3 Intense 4 Light 2 8 4

7 5 6 3 Mean B. cockerelli0.1 0.2 0.3 0.4 0.5 per trap per field 3 6 9 1 2 3 0 1 2 3

May 0 “Intense” sticky traps sticky “Intense”

1

Upper Snake Magic Valley Treasure Valley 2

3 Jun

4

5

6

7

8 Jul

9

10 11

12 Aug 13

14

15 16 Sep 17 18

19 2013 2012 2015 2014 20 21 22

9

8 2012 2013 pertrap perfield 2 2014 2015

cockerelli 1 B.

0

Mean 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 Week Number “Light” sticky traps 1.0 2013 0.8 Treasure Valley 0.6 Elmore County Magic Valley 0.4 Upper Snake 0.2 per trap per field per trap

2014 0.4 0.3 cockerelli 0.2 B. 0.1 0.0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Mean Mean May Jun Jul Aug Sep Week Number 4 3 Treasure Valley 2012 2 Magic Valley 1 Upper Snake 4 3 “Intense” vacuum samples 2013

per sample per sample per field 2

1 4

cockerelli 3 2014

B. 2 1

Mean Mean 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 Week Number 20 15 Treasure Valley 2012 10 Magic Valley 5 Upper Snake 0.12 0.09 “Intense” leaf samples 2013

per sample per sample per field 0.06

0.03 0.12

cockerelli 0.09 2014

B. 0.06 0.03

Mean Mean 0.0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 Week Number 33 of 1,093 psyllids Lso+ (2.8%)

Full Season, 2013 No psyllids ≥1 cold psyllid ≥1 hot psyllid 2012 2013 2014 2015

Total sites 15 14 + 94 = 13 + 75 = 13 + 71 = 108 88 84 Traps per week (approx.) 150 516 430 414

Weeks of trapping 19 19 19-22 18-22

Total psyllids on sticky 1,603 1,093 170 1,126 cards Total psyllids tested for Lso 1,073 1,093 170 1,126

Lso positive psyllids 250 33 4 39

% Lso positive 23.3% 2.8% 2.4% 3.5%

Total cards read (approx.) 2,850 9,804 8,560 7,452

Psyllids per card (approx.) 0.56 0.11 0.02 0.15

ca. 8 times higher incidence of Lso in 2012 vs. 2013-2015 ca. 5-fold drop in psyllid abundance each year until 2015 Where do potato psyllids come from?

• Native to North America (west of Mississippi) • Overwinter in southern US / northern Mexico and migrate north with high temperatures (?) • Greenhouses? • Overwinter in PNW • feed on plants in >20 plant families

Where do potato psyllids come from?

• Native to North America (west of Mississippi) • Overwinter in southern US / northern Mexico and migrate north with high temperatures (?) • Greenhouses? • Overwinter in PNW • feed on plants in >20 plant families

Adults observed overwintering in PNW on bittersweet nightshade during winters of ‘12, ‘13, ’14, ‘15 Off-season psyllid monitoring

• Started during Spring 2013 • Magic Valley: 4-5 sites

Erik J. Wenninger • Treasure Valley: 4 sites • Sticky cards and vacuum bittersweet nightshade Erik J. Wenninger samples • Fortnightly sampling

Erik J. Wenninger Sticky card sampling at bittersweet nightshade sites

0.9 0.8 Treasure Valley 0.7 Magic Valley 0.6

0.5 per trap per site per trap 0.4

0.3 started Treasure 0.2 Valley sampling cockerelli 0.1 B.

0.0

Jul Jul Apr Apr Oct Oct Jan Jun Jun Feb Mar Mar Aug Dec Nov Sep Aug Nov Sep May May

Mean Mean 2013 2014 Vacuum sampling at bittersweet nightshade sites

10 site 9 Treasure Valley per 8 Magic Valley 7 6 sample sample 5

per 4

started 3 Treasure 2 Valley sampling 1 cockerelli

0

B. Jul Jul Apr Apr Oct Oct Jan Jun Jun Feb Mar Mar Aug Dec Nov Sep Aug Nov Sep May May

2013 2014 Mean Mean Alternative host plants • Greenhouse trials screening various weeds, crops, and native plants for suitability as hosts to potato psyllids Potato psyllid haplotypes (biotypes)

Swisher et al. 2014 Western Central Northwestern Southwestern Relative abundance of each haplotype 2012 2014 (from Swisher et al., 2014)* 2013

100% 100% 100%

90%

90% 90% 80% 80% 80% 70% 70% 70% 60% 60% 60% 50% 50% 50% abundance abundance 40% 40% 40% 30% 30% 30% Relativeabundance 20% 20% 20% Relative Relative 10% 10% 10% 0% 0% 0%

Collection month Collection month Collection month

* Swisher et al., Am. J. Potato Res. (March 2014) Lso haplotyping : results

2012 2013 75% of the Lso samples 50% of the Lso samples haplotyped haplotyped Most are hapA All are hapA But 2 are hapB

First description of Lso 2014 hapB in Idaho 4/5 Lso samples haplotyped hapB increasing?

2 hapA, 2 hapB Conclusions • Psyllid phenology related to elevation / temperature gradient across Idaho • Psyllids: 2012 > 2013 > 2014… 2015 • Lso high in 2012; more “typical” 2013-2015 • ZC nil 2013-2014 • Suggests monitoring program is effective at predicting ZC risk • Early psyllids in 2015  ZC?

Acknowledgements • Idaho Potato Commission • PNW Potato Research Consortium • Idaho State Department of Agriculture • Idaho Agricultural Experiment Station • USDA-TASC • Chemical industry • Amy Carroll, Lynn Woodell, Lucy Standley, Jessica Vogt, Tasha Stanzak, Cheryn Clayton, Neyle Perdomo, Vince Adamson, Tucker Daley, Kortni Cox, Aaron Vogt, Carlie Wilkinson, Jesica Lowe, Kyanne Frandsen, Chelsea Stevens, Ethan Whitten, Kevin Robison, and Trent Taysom • Jennifer Riebe, Tom Salaiz, Drew Glascock, Katherine Long, Megan Williams, Paul Stukenholtz, Janan Claiborn, Dusty Danos