Pyrenopeziza Brassicae (Sutton and Rawl): Light Leaf Spot Ascomycetes: Helotiales Date: May 14, 2015 Highlights

NPAG Notice New Pest Advisory Group (NPAG)

Pyrenopeziza brassicae (Sutton and Rawl): Light leaf spot Ascomycetes: Helotiales Date: May 14, 2015 Highlights:

• Light leaf spot (LLS) is an important disease of • Pyrenopeziza brassicae affects crop yields brassicas in temperate regions. and/or costs of production of cruciferous crops, • Most cruciferous crops are susceptible to P. although the extent to those impacts is brassicae, including rapeseed, canola, unknown. cauliflower, Brussels sprout, turnip, radish and • Symptoms include discolored brown lesions and kale. Oilseed rape is highly susceptible to this margins, leaf death or distorted young leaves, pathogen. and brown lesions on stems. • Areas where P. brassicae could potentially • Infections are not visible until 2-3 months after spread in the United States include the mid- infection. Atlantic region, areas south of that region, and • In Europe, canola seed production loss of up to the Pacific coast within Plant Hardiness Zones 7- 22% has been observed. 9. • Control of P. brassicae includes use of resistant • Methods of P. brassicae spread include wind cultivars, debris management, protectant dispersed ascospores or rain-splash dispersed fungicide application, rotation to non- conidia. cruciferous crops, and control of susceptible • Long-distance dispersal of P. brassicae can cruciferous weeds. occur through the dispersal of infected seeds. • PPQ-Agriculture Quarantine Inspection developed guidelines fungicide seed treatments to mitigate P. brassicae (see below).

Need for new technology or knowledge: Additional Information:

• Determine the level of susceptibility of crucifers • PPQ Operatives: Access the full NPAG report at: produced in the United States to P. brassicae. http://npag.cphst.org/index.cfm • Determine the phytosanitary risk of P. brassicae • Operatives outside of PPQ: Send information to canola production in northern regions of the requests to [email protected] United States. • Determine the risk of seed-borne inoculum to brassica vegetables and forage production fields.

Tara Holtz, Chair USDA/APHIS/PPQ/CPHST/PERAL Cynthia B. Landry, Vice Chair I [email protected] 1730 Varsity Drive, Suite 300 Betsy Randall-Schadel, Vice Chair II (919) 855-7423 Raleigh, NC 27606-5202 [email protected] Pyrenopeziza brassicae NPAG Notice20150514.docx Page 1 of 2 Pages

NPAG Notice Pyrenopeziza brassicae May 14, 2014

Seed treatments guidelines for Brassica spp. to control light leaf spot (Pyrenopeziza brassicae)

Fungicide seed treatments with documented activity on Pyrenopeziza brassicae are listed in the table below. The table lists fungicides by FRAC code, group name, common name, examples of trade names, and references. The fungicides listed are examples for each group, but there may be more fungicides with labels available. The fungicide groups with activity on Pyrenopeziza brassicae are MBC (1), DMI (3), succinate-dehydrogenase (7), and QoI (11). Brassica seed must be treated with as many different FRAC groups as possible to avoid development of resistance to the fungicides. It is common practice to use multi-site fungicides such as thiram and Pythium/Phytophthora-specific fungicides such as metalaxyl with the P. brassicae fungicides. For the best control of P. brassicae, use the highest dose rate on the label for each fungicide.

Foliar fungicide applications need to be made in conjunction with the fungicide seed treatments. All foliar applications must be tank mixes of multisite fungicides and include at least two fungicides with activity to P. brassicae. For best control of P. brassicae, use the shortest spray interval and the highest dose on the EPA fungicide label.

The applicator must follow a fungicide resistance management program on the EPA label.

FRAC Group name Common Resistance Fungicide EPA Crops References code ** name documented seed REG treatment No. 1 MBC carbemdazim Yes (1), (2) 1 MBC thiabendazole Yes Mertect 100- Brassica (1) 340-F 889 3 DMI ipcopazole Rancona 400- Brassica, (1) 3.8 FS 544 mustard, rape, canola 3 DMI metaconazole Metlock 59639 Canola (1), (2), (3) -171 3 DMI prothioconazole (3) 3 DMI tebuconazole Yes (1), (2), (3) 7, 11 Carboxamides Boscalid Coronet 100- Brassica, (1) QoI pyraclostrobin 1159 rapeseed 11 QoI azoxystrobin Dynasty 100- Brassica, (1), (2) 1159 Canola 7, 11 Carboxamides penflufen Prosper 264- Canola, (1) QoI trifloxystrobin EverGol* 1121 rapeseed, mustard * Prosper also has clothianidin and metalaxyl ** Group name abbreviations correspond to the following (FRAG-UK, 2013): MBC = methyl benzimidazole carbamate; DMI = demethylation-inhibiting; and QoI = Quinone outside inhibitor.

References: (1) FRAG-UK 2013. Fungicide resistance management in oilseed rape. Fungicide Resistance Action Group – UK. http://www.pesticides.gov.ukrags.asp?id=644. (2) Karolewski, Z., and Kosiada, T. 2010. Sensitivity of Pyrenopeziza brassicae (light leaf spot) populations to fungicides recommended for the fungus control. Phytopathologia 56:59-65. (3) Oxley, S.J.P., and Walters, D. R. 2012. Control of light leaf spot (Pyrenopeziza brassicae) on winter oilseed rape (Brassica napus) with resistance elicitors. Crop protection 40:59-62.