Understanding and Managing Walnut Botryosphaeria/Phomopsis Canker and Blights (Influence of El Niño on the Sleeping Giant) Themis J. Michailides D. Morgan, J. Moral, D. Felts, R. Puckett, M. Luna U N I V E R S I T Y O F C A L I F O R N I A Kearney Agricultural Research and Extension Center & University of California Cooperative Extension Quad-County Walnut Institute, Stockton 15 March 2016 Cooperators: J. Hasey, R. Buchner, B. Coates, K. Pope, K. Anderson, J. Grant, and D. Lightle: UCCE Sutter/Yuba/Colusa, Tehama, San Benito, Yolo/Solano, Stanislaus, San Joaquin, and Butte/Glenn counties, respectively
El Niño winters in California (1982 through 2015) Winter 1982-1983 El Niño storms Winter 1994-1995 winter storms Winter 1997-1998 El Niño storms
The Bot disease started in 1983, probably in the oldest pistachio orchard in the State (Butte Co., CA)
El Niño winters in California (1982 through 2015) Winter 1982-1983 El Niño storms Winter 1994-1995 winter storms Winter 1997-1998 El Niño storms
1995
El Niño winters in California (1982 through 2015) Winter 1982-1983 El Niño storms Winter 1994-1995 winter storms Winter 1997-1998 El Niño storms
Bot epidemic of 1998
because of Botryosphaeria blight
Winter 2015-2016 El Niño?
Botryosphaeria /Phomopsis of walnuts in Spain
Symptoms we expect to see in walnut orchards in an El Niño year in California
% Infection (%) Latent infection of fruit: Blighted fruit and pathogen isolation from kernels of walnut fruit inoculated with Lasiodiplodia citricola 120.0 100.0 80.0 bc Brighted fruit Isolation from kernel bc abc Lasiodiplodia citricola abc A a ab Blighted fruit 60.0 c A A 40.0 20.0 B B B B AB infected kernels 0.0 5/12 5/22 6/1 6/11 6/21 7/1 7/11 7/21 7/31 8/10 8/20 8/30 9/9 120.0 May 100.0 80.0 c blighted fruit Isolation from kernel c c Neofusicoccum parvum a bc bc Sept. B ab
Infection of intact fruit in the orchard All Botryosphaeria & Phomopsis species Fruit Fruit Peduncle Infect spurs/shoots
Spurs with cankers covered with sporulation (pycnidia)
Susceptible walnut cultivars Ashley Chandler Howard Tulare Vina Serr Hartley Payne Dixon Livermore
Botryosphaeriaceae Phomopsis Distribution of Botryosphaeria spp. in walnut orchards N. mediterraneum = widespread
Botryosphaeria dothidea Neofusicoccum spp. Lasiodiplodia spp. Diplodia seriata Neoscytalidium**
Perithecia Pycnidia
Oozing pycnidia of Botryosphaeria on walnut spurs 0 water Rain: water Oozing pycnidia
The majority of spores will be released within 30 minutes
Spores of Botryosphaeria they germinate within 1.5 hours wetness!
Germination under adverse (wet/dry/wet) conditions and surviving mechanisms
Botryosphaeria spread rain & moving water in the orchard +++++++* air (airborne ascospores) ++ pruning equipment + insects? *rain, dew, sprinkler irrigation
Conditions for infection events Presence of inoculum Rain: at least 1/4 Temperature: 50 F Presence of susceptible tissues
Cankers associated with pruning wounds
Susceptibility of pruning wounds of 1-, 2-, 3-, & 4-16 year-old wood to infection by Bot Average canker length (cm) 14 12 10 8 6 4 2 e cde de a bcd abc bcd a ab b cd abc b 0 control Pruning on 9 & 10 Feb 2015 0 day 3 day 1 week 2 week 3 week 4 week 8 week 12 week 16 week Post-pruning inoculation date
Prune branch Walnut branch Walnut branches
Susceptibility of pruning wounds to infection by Bot as affected by age Average canker length (cm) 16 14 12 10 8 6 4 2 0 Pruning on 9 & 10 February 2015 up to 2 inches b b 5-6 inches 1 year 2 year 3 year 4 year Age of inoculated shoots a a
Treatment of pruning wounds with fungicides and then inoculation with Neofusicoccum parvum 10 Average canker length (cm) 8 6 4 2 a b Neofusicoccum parvum ab ab b 0 Control Quadris Top Merivon Merivon+VitiSeal Abound
Wounds in the field during 1) the season, 2) at harvest and 3) postharvest Leaf scars * Peduncle scars * Canker * Fruit scars when walnuts drop
Infection Courts of Botryosphaeria and Phomopsis During the season: At harvest: Wounds from hail, freeze, Scars from peduncles sunburn, wood peckers Fruit wcars Pruning wounds Postharvest: Leaf scars Scale wounds Peduncle scars Mechanical wounds Walnut blight Leaf scars lesions Husks (remaining on the tree) Pruning wounds Wounds from freeze damage Injuries from wood peckers Other type of injuries
Leaf scar infections
Injuries (wounds) by walnut scale & Botryosphaeria walnut scale Injuries from scales Necrotic lesions More than 50% of necrotic lesions had Botryosphaeria spp.!
Management of Botryosphaeria canker and shoot blight: 1. Assessment of Bot inoculum risk: BUDMON, or CANCERED SPURS ( in progress). 2. Cultural control: Sanitation: prune infected shoots to remove cankers and reduce spore inoculum; avoid wetting the tree canopy. 3. Chemical control: Apply fungicide sprays. Best control Integrated disease control: Use all of the above (1 + 2 + 3).
BUD MONitoring (= BUDMON) Technique BOT BOT Bud collection: February/March Results in 6-7 days % of buds with Bot
Sanitation by pruning
Walnut prunings
Presence of pycnidia with viable spores % Viability Bot survival in chipped wood 120 100 80 60 40 20 0 Unchipped Chipped c/o Katherine Pope, UCCE Yolo /Solano
Botryosphaeria. 40% Phomopsis.. 30% Botryosphaeria + Phom.. 20% No pycnidia....10% 90% Compost Botryosphaeria.. 0% Phomopsis.. 0% Botryosphaeria + Phom.. 0%
Effects Montgomery of fungicides fungicide on Botryosphaeria efficacy 2014 in seasons Chandler walnut shoots/spurs all treatments (Butte Co.) - 2014 SPRAYS: May 8, June 12, and July 10 Merivon Quash Ph-D + Tebucon K Phite Fontelis + OR009 K Phite + Latron EXP 1 + EXP 3 EXP1 + EXP 2 Luna Sensation 7.6 oz EXP 1 Pristine Luna Experience 10 oz Fontelis + Tebucon Luna Experience 6 oz Badge + Manzate Ph-D Fontelis Quadris Top Viathon Luna Sensation 5 oz Control a aa 4X a a ab ab ab ab ab ab ab ab ab ab ab abc abc abc bc c 0 2 4 6 8 10 12 14 Blighted shoots spurs (%)
Nuts at harvest No discoloration Brown kernels Isolations on agar media Black kernels
Effects of fungicides on Botryosphaeria in Chandler walnut (black and brown kernels) (Colusa Co.) - 2014 Botrysphaeria spp. (%) 10 8 6 4 2 0 a ab ab Control Luna Experience (1) Luna Experience (2) Black kernels ab Quadris Top (1) Quadris Top (2) Merivon (1) Merivon (2) b b b b Fontelis+Tebucon (1) Fontelis+Tebucon (2) b Botryosphaeria spp. (%) 8 6 4 2 0 a ab Control Luna Experience (1) Luna Experience (2) b Brown kernels Quadris Top (1) Quadris Top (2) Merivon (1) Brown kernels ab ab ab ab Merivon (2) Fontelis+Tebucon (1) b b Fontelis+Tebucon (2)
Efficacy of four calendar sprays of fungicides in a Chandler walnut orchard in Butte Co. (Sacramento River) - 2015 SPRAYS: May 12, Jun 11, Jul 10, Aug (4X SPRAYS) Pristine Ph D + Tebuconazol Fontelis + Abound Font-Teb>QuadTop>Font-Teb>QuadTop Indar Fontelis + Vintre Luna Experience Viathon Quadris Top Fontelis + Tebuconazol Quash Luna Sensation Ph D Badge-Manzate Pro Stick Fracture Merivon Fontelis Control a ab ab ab ab ab abcd abc abc abc abcd abcd abcd abcd bcd bcd bcd cd d 0 1 2 3 4 5 6 7 8 9 Blighted spurs (%)
Leaf wetness model (LWM) where rain exceeded threshold in a Chandler walnut orchard in Butte County 60 Leaf wetness, hours 50 40 30 20 sprayed April 8-9 (8 mm) Medium Risk High Risk sprayed April 24-25 (18 mm) sprayed Sept. 16-17 (3 mm) 10 0 Low Risk 5 10 15 20 25 Temperature, C
Various timings of Merivon fungicide in a Chandler walnut orchard in Butte Co. - 2015 Merivon: bloom, May, June, July Merivon: April 9, 26; Sept 17--leaf wet Merivon: May, June, July, post-harvest Merivon: post-harvest Merivon: May, June, July erivon: bloom, May, June, July, post-harvest Merivon: bloom, post-harvest a ab abc Bloom + Standard calendar 4X Leaf wetness model 3X Standard calendar+postharvest 4X bcd cde cde cde 1X Standard calendar 3X 5X? 2X Merivon: bloom de 1X Control e 0 1 2 3 4 5 6 7 8 9 SPRAYS: Calendar: May 12; Jun 12; Jul 10 = 3X Blighted spurs (%) Bloom: Apr 9 = 1X; Postharvest: Nov 3 = 1X
Best-timing of a single spray of Merivon in a Chandler orchard in Butte Co. - 2015 5.0 4.5 ab Bloom ab Postharvest (PH) Blighted spurs (%) 4.0 3.5 3.0 2.5 2.0 1.5 ab Best timing a a ab Nonsprayed = 8% 1.0 Merivon: bloom Merivon: May Merivon: June Merivon: July Merivon: August Merivon: post: harvest SPRAYS: Apr 9 (bloom); May 12; Jun 12; Jul 10; Aug 10; Nov 3 (PH)
www.ipm.ucdavis.edu
Efficacy of registered fungicides against Botryosphaeria canker and blight of walnut Fungicide Active ingredient Efficacy Quash Merivon. Pristine. Quadris Top.. Switch PhD... Viathon.. K-Phite. Luna Experience Luna Sensation Fontelis Manzate metconazole fluxopyroxad+pyraclostrobin boscalid + pyraclostrobin difenoconazole + azoxystrobin cyprodinil + fludioxonil Polyoxin-D tebuconazole + phosphite Polyphosphite fluopyram + tebuconazole fluopyram + trifloxystrobin penthiopyrad copper-mancozeb ++++ ++++ +++ +++ ++++ +++ +++ ++++ +++ ++ +++ ++ Efficacy: + = poor: ++++ = excellent http://www.ipm.ucdavis.edu
Scenarios for sanitation & sprays Orchards - Heavy infection (>50%): Prunings need to be chipped and they may be left in the orchard; apply 3-5 fungicide sprays ((bloom, May, Jun, July, and postharvest). Orchards - Moderate infection (21% - 50%): Prune or hedge these orchards first and then move into heavily infected orchards; prunings need to be moved out of the orchard; at least 3 sprays (bloom and June spray, & July depending on weather conditions). Orchards Light infection (6% - 20%): Prune or hedge these orchards first and then move into more infected orchards; prunings need to be moved out of the orchard; two sprays (bloom and mid June to early July). Orchards Very light infection (1% - 5%): Prune infections and destroy them out of the orchard; no spray(s) needed, unless it rains. Orchards No infection: no Botryosphaeria yet (0%): Prunings can be chipped and left in the orchard; no spray(s) are needed.
CONLCUSIONS For best management we need all: a) assessment of inoculum risk; b) sanitation; and c) fungicide sprays. Sprays during May through July/August reduce Botryosphaeria (confirmed in 2014 & 2015). Bloom sprays and postharvest sprays seem to reduce disease (we need to repeat in 2016). Sprays after a rain/infection event seem to be very effective (we need to repeat in 2016). The best-timing spray seems to be around mid-june to early/mid July (we need to repeat in 2016).
Acknowledgments UC Kearney Agricultural Research & Extension Center David Morgan Dan Felts Yong Luo Ryan Puckett Juan Moral & farm advisors Thank you
Effect of walnut scales on infection of walnut by Botryosphaeriaceae (cv. Vina) Percentage of walnut branches infected 20% 18% 16% 14% 12% 10% 8% 6% 4% 2% 0% Shoots w/ scales a b L as iodiplodia c itric ola Inoculation Without wounding spore suspension Shoots w/ scales a b Neofus ic oc c um parvum Shoots w/ scales a b Neofus ic oc c um mediterraneum C ontrol With s c ales No s c ale Treatment 60-75% more shoots were infected when scales were 3 weeks after inoculation present than when scales were not present