Research on hop downy mildew in Ontario

Transcription

1 Research on hop downy mildew in Ontario Is it related to cucumber downy mildew? Mary Ruth McDonald, Amy Fang Shi, Cathy Bakker, Catarina Saude

2 Prof. Mary Ruth McDonald Dept. of Plant Agriculture, Univ. of Guelph Plant pathology and integrated pest management of vegetable crops and specialty crops Production and management of vegetable crops

3 HOP AND CUCUMBER DOWNY MILDEWS - CROSSINFECTION OF CUCUMBERS AND HOPS RESEARCH UPDATE C. Saude, C. Bakker and M.R. McDonald Originally presented Nov to the Fresh Vegetable Growers of Ontario This project was funded by the Fresh Vegetable Growers of Ontario

4 Cucumber 3083 A harvested (OMAFRA, 2012) 32,835 tonnes Both fresh and processing Cucumber downy mildew a serious problem

5 Cucumber Downy Mildew Pseudoperonospora cubensis Fungus-like water mould Pathogen of cucurbits: - cucumber, cantaloupe, melon, gourds, squash, pumpkin Infects leaves, decreasing photosynthesis

6 Cucumber Downy Mildew Pseudoperonospora cubensis Can not survive the winter in host plants in northern latitudes Survives in host in warm temperate (FL) to subtropical regions In Ontario - Where does it come from or overwinter?

7 Cucumber Downy Mildew Pseudoperonospora cubensis Disease control has been difficult ~ 10 products registered to control cucumber Downy mildew 2010 to 2012: -Efficacy trials conducted at SRS -Combined with spores monitoring Conventional (18) and organic (9) 4 to 6 sprays applied

8 Hop Perennial crop Several cultivars Hop Downy mildew- major problem

9 Hop Downy Mildew Pseudoperonospora humuli Fungus-like water mould Pathogen of hop Infects rhizomes, leaves, and cones Overwinters in rhizomes as mycelia in buds No races or strains known

10 Cucumber and Hop Downy Mildews Cucumber downy mildew Pseudoperonospora cubensis Hop downy mildew Pseudoperonospora humuli Look very similar Can not be differentiated using basic molecular methods Can Ps. cubensis infect hops? Can Ps. Humuli infect cucumbers?

11 Hop Downy Mildew Pseudoperonospora humuli V. Brewster, Compendium of Hop Diseases and Pests

12 Objectives 1. Survey hop yards for hop Downy mildew 2. Investigate possible cross infection of Ps. cubensis and Ps. humuli on hop and cucurbits and determine if: - Cucurbits can be infected by Ps. humuli isolates from hop - Hops can be infected by Ps. cubensis isolates from cucurbits

13 Materials and Methods Ps. humuli and Ps. cubensis Cucumber and Hop infection Cucumber cultivar: Marketmore 10 plants/run Hop cultivar: Nugget 10 plants/run Ps. cubensis collected from cucumber plots at Simcoe Research Station Ps. humuli collected from Simcoe Research Station hop yard 5 Leaves/plant infected with 5 droplets (25 μl) of each inoculum (10 4 /ml) Plants kept in growth chambers (4 weeks; 18-20ºC, high RH) Lesions and pathogen spread evaluated and re-inoculated to natural host Spores collected from lesions for DNA comparisons

14 In 2013: Results - High cucumber Downy mildew pressure - High hop Downy mildew pressure Hop Downy mildew found in Norfolk- Niagara cluster Disease monitored in three hop yards in Norfolk 2014 very little downy mildew- no data Downy mildew found on wild hops in Guelph area

15 Results Cucumber Downy mildew - Hop and cucumber infection - Cucumber lesions larger ( cm) heavy sporulation - Hop lesion smaller ( cm) mild sporulation Hop Downy mildew - Cucumber and hop infection Not completed in 2013, 2015?

16 Cucumber Downy Mildew - Hop and Cucumber Infection Lesion Length (cm) Cucumber Hop Plant #

17 Conclusions Downy mildew from cucumber can infect hops Downy mildew from hops infection of cucumber unknown at this stage First results suggest that downy mildew from cucumber in not a major threat for hops but much more work is needed

18 OMAFRA/Univ of Guelph project Origin, biology and management of Hops Down Mildew: a threat to hops, cucumbers and other crops - Identification and characterization of hop downy mildew, its effect on hop and cucumbers by: Surveying yards and wild hops for Ps. humuli isolates present in Ontario. Compare to survey data on cucumber downy mildew from OMAF extension specialists. - Understanding the systemic infection and overwintering of downy mildew in hop crowns.

19 OMAFRA/Univ of Guelph project Origin, biology and management of Hops Down Mildew: a threat to hops, cucumbers and other crops Continuing initial work examining cross infectivity of Pseudoperonospora humuli and Pseudoperonospora cubensis) on cucurbits and hop Determining if Ps. humuli is present in hop plants and rhizomes arriving in Ontario from the United States. Spring 2015 and Identification and characterization of cone pathogens, such as Botrytis spp. and Alternaria spp.

20 Future Work? Evaluate fungicides and biological controls Evaluate cultural controls pruning Disease forecasting? One big question: is there a need to reestablish the hop yard at Simcoe for further research? Where will the funds come from for this? AAFC is looking at some further work on cucumber downy mildew

21 Acknowledgements Agriculture and Agri-Food Canada through the Canadian Agricultural Adaptation Program (CAAP) Agricultural Adaptation Council (AAC) Fresh Vegetable Growers of Ontario Ontario Hop Growers Association Hop and Cucumber growers Lisa Weber and Kevin Robinson

22 Questions?

23 Cucumber Downy Mildew

24

25 Future Work Continue the ongoing work examining cross infection of Ps. cubensis and Ps. humuli - Plants and molecular work Examine cross infection between Ps. humuli and Ps. cubensis isolates from other cucurbits - cantaloupe, melon and squash

26 Cucumber Downy Mildew Host Cucumber Downy Mildew Pathotypes (strains) Cucumber Cantaloupe Sweet melon Sour melon Watermelon Pumpkin & Squash Exists as pathotypes varying in ability to infect the various cucurbit types Races and strains have been described within pathotypes based on variation in virulence and fungicide sensitivity