Management of Fusarium root rot on carrots Kevin Vander Kooi Mary Ruth McDonald Ahmed Abdelmagid Michael Tesfaendrias

Fusarium Root Rot of Carrot Fusarium root rot was identified in the Holland Marsh, Ontario in 2008 Fusarium solani is a soil-borne pathogen but can also be associated with seed This disease infects both the root and crown of carrots, significantly reducing the marketable yield Currently, there is no registered fungicides to control the disease Fusarium solani macro and micro condia

Project Objectives Field trials were conducted between 2011 and 2015 in carrot fields with a history of the disease to: Evaluate the susceptibility of carrot cultivars to Fusarium root rot in field Screen fungicides for effectiveness in controlling the disease Evaluate soil fumigants

Screening Trials 2011-2013 2011- two fungicides: Maxim (fludioxonil 21%) Field 1 Scholar (fludioxonil 230 g/l) Field 2 2013 – five products (In-furrow) Emesto Silver (Penflufen 9.4% and Prothioconazole1.7%) Mertect (Thiabendazole 42.3%) Folicur (Tebuconazole 43% ) Heads Up (Saponins of Chenopodium quinoa 49.65%) Trichoderma atroviride 2012 - 2014 – Variety Trials Field trials Lab trials

Fungicide Trial 2011 NS

Fungicide Trial 2013 September Harvest

Results Disease infects carrots late in season in the field and can cause significant yield losses None of the fungicides or biologicals reduced disease incidence Fusarium solani was identified as the pathogen

Fusarium root rot lab trial Cellobunch vs Isolate 2 Envy vs Isolate 1 Fontana vs Isolate 2

Variety trial in lab Fusarium solani (isolate 1) abc bcd cd d e a de

Variety trial in lab Fusarium solani (isolate 2) bc cd d e

Cultivar field trial - 2013 NS ns

Variety Trial Results Identified different isolates of the pathogen in the Holland Marsh Different isolates of the pathogen infected carrot cultivars under controlled conditions and caused disease All carrot cultivars tested were susceptible to Fusarium

Evaluation of Pic Plus fumigant for control Fusarium root rot Pic Plus (Chloropicrin 85%) Labelled for use in carrots in 2012 Affects a broad spectrum of fungi, nematodes, insects Injected into soil prior to seeding carrots Broadcast and banded applications of 108 L/ha Use in Bradford/Holland Marsh spring 2013 Issues with product in summer of 2013 in SW Ontario In 2014 PMRA requirements for fumigants changed

Pic Plus Applications Banded application Applied at seeding Tested several rates

Evaluation of Pic Plus-2014

Marketable yield following treatment with Pic Plus Marketable Yield t/ha

2015 Harvest Results Several rates tested Applied at seeding under the carrots 108 L/ha reduced disease Issue with quality – forked roots

108 L/ha

Check

54 L/ha

70 L/ha

Fumigant Results Pic Plus is the only product that significantly decreased the disease incidence under field conditions Higher rates up to 108 L/ha reduced disease incidence and severity Use of high rate at seeding caused forking

Recommendations If using high rate delay seeding for several days Avoid late harvest As the plants mature and carrots bulk up the roots become more susceptible to root rot Minimizing stress Anything that stresses the plant such as herbicide injury, or drought may make it more susceptible to root rot Further research is needed to find effective rates to decrease Fusarium severity

Thank you Annual Muck Growers Conference April 12-13 Bradford Ontario All research reports available online www.uoguelph.ca/muckcrop

Acknowledgments TriEst Ag Group Inc. (Douglas Ag Services) HMGA through the Bradford Coop Plant Productions systems of the OMAFRA and University of Guelph partnership Cooperating growers