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Soybean and SunflowerDisease survival of Diaporthe/Phomopsis spp may
require changed cultural practices
A Case Study
By Sue Thompson – DAFFQ, ToowoombaGRDC DAFFQ IDM project: DAQ 000186
This Powerpoint presentation is an extract from a presentation delivered at a soybean research meeting in Griffith, NSW on 23 September 2014
Phomopsis pod and stem blight (Diaporthe spp.)
On soybean – Phomopsis stem and pod blightOn sunflower – Phomopsis stem canker
• Common in coastal farming systems• Infection favoured by prolonged rainfall• Survives in seed, infected stubble and on weeds• Symptoms often not noticed until plant begins to senesce• Stem, petiole lesions and/or pycnidia may be seen in vegetative stages.
• Pycnidia can be seen on pods as they mature.• Seed quality reduced by cracking, shrivelling and mould growth• Pith damage from stem lesions may lead to smaller seeds
Diaporthe fruiting bodies (pynidia) and oozed droplets of spores on seed
Symptoms can be confusing…
Diaporthe sp. Macrophomina phaseolina (Charcoal Rot)
Colletotrichum sp. (Anthracnose)
Bottom photo: H Brier / J Wessles DAFFQ
Symptoms can be confusing…..
Weathering
Charcoal Rot
Phomopsis pycnidia (small black dots)and fluffy growth around seeds
Symptoms on green plants….
Symptoms are often not seen until plants reach maturity…
Early senescence and pycnidia on stems and/or pods
Where does Diaporthe inoculum come from?
Living hosts – ‘Green bridge’
• Crops
• Crop volunteers
• Weeds • Noogoora Burr • Saffron Thistle• Wild Sunflower • Bathurst Burr • Cobblers Peg
Infected soybeans Clifton Q
Common weed speciesWild Helianthus annuus
Noogoora Burr ‐ lesion and developing fruiting bodies
Where does Diaporthe inoculum come from?
Dead hosts – ‘Brown Bridge’
• Stubble• Soybean stubble• Sunflower stubble
• Weed residues• Noogoora Burr • Turnip weed • Thornapple stubble• Thistle residues (scotch, sow)
Basal lesion on Thornapple
Disease survival on stubble/stems in low till systems
Fruiting bodies of Diaporthe spp on ‘dead’ soybean stems
Diaporthe/Phomopsislesions on sunflower
• Control weeds in‐crop• Control weeds adjacent to paddocks, on roadsides• Control crop volunteers
Consider • Incorporation of crop stubble• Incorporation of dead weed residues
This has some implications for zero and minimum tillage systems…..
How to reduce Diaporthe inoculum in the field
Weeds survive on roadsides and paddock verges
Moree, NSW
20 yrs + of Zero and Min Till – the upside…• Home for beneficial insects
• Moisture savings
• Energy savings
• Compaction reduction
• Weed control (herbicides) – stubble can inhibit weed emergence
20 yrs + of Zero and Min Till – the downside… x• Herbicide ‐ resistance x
• Environmental concerns x
• Protection for insect pests eg. Lucerne Crown Borer x
• Protection and increased survival for multiple pathogens x
Diaporthe sp on wild sunflower stubble
• Sclerotinia minor, S. sclerotiorum, Sclerotium rolfsii – 100+ hosts
• Fusarium spp. – sorghum stalk rot, corn cob rot, wheat crown rot
• Phoma (Ascochyta) rabiei – leaf, stem and pod infection chickpeas
• Leptospheria maculans ‐ blackleg on canola
With little or no cultivation in these systems these diseases can also potentially be carried over into the following crops through stubble/weed residue retention
Other pathogens surviving in zero and minimum till
Sorghum stalk rotThistle stem with sclerotesof Sclerotinia
Ascochyta blight on chickpeas
Specific pathogens isolated from dead hosts
Alternaria brassicae (leaf spot)• isolated from turnip weed• damaging pathogen of brassicas
Cochliobolus sativus (root rot)• isolated from sunflower stubble• root rot, leaf and seed pathogen of wheat
Colletotrichum gloeosporioides (anthracnose)• isolated from soybean stubble and unidentified weed residues• causes fruit rots (avocado, mango), stem and pod blight on soybeans
Macrophomina phaseolina (charcoal rot)• isolated from multiple crop and weed residues• significant pathogen of sorghum, soybean, maize, sunflower
Stenocarpella maydis (cob rot)• isolated from maize residues• pathogen of maize
Charcoal rot on sunflower
Corn cob rot
Dead, not gone…..• Inoculum reservoirs of multiple pathogens are present in the field, regardless of
presence of crop hosts
• Some of those fungi will be pathogenic to at least one of the crops in the summer farming system in the Northern region.
• Dead weeds as well as crop stubble can be a inoculum reservoir for future disease and insect outbreaks.
• Zero and min tillage systems contribute to survival of some pathogens and insects
• Some weeds in non cropping ecosystems also harbour significant crop pathogens.
• Destroy the Brown Bridge………………….. Consider Strategic Tillage!
Acknowledgements…• Roger Shivas ‐Mycology and Taxonomy: DAFFQ Biosecurity, Brisbane• Yu Pei Tan ‐Molecular Analyses: DAFFQ Biosecurity, Brisbane• (Anthony Young DEEDI/BSES 2010)• Stephen Neate ‐ PhD supervisor: USQ, Toowoomba• Liz Aitken ‐ PhD supervisor: UQ SAFS, St Lucia• Australian Sunflower Assoc (ASA) • Australian Oilseeds Federation (AOF)• DAFF QLD• GRDC• Gordon Cumming – Pulse Australia• Growers and advisors in all regions – thank‐you!!• Loretta Serafin ‐ NSW DPI, Tamworth, NSW• Mal Ryley ‐ USQ, Toowoomba • Ian Morgan – PB Agrifoods• Seed Companies: Avosun, HSR Seeds, KB Ornamentals, Nuseed,
Pacific Seeds• Tom Gulya ‐ USDA Fargo ND• University of Queensland • Photos: S Thompson DAFFQ and H Brier / J Wessles DAFFQ
Email: [email protected]: 0477 718 593
Grafton Soybean Varietal Trial Site 2014