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PestFacts WA

Sclerotinia apothecia

  • Albany DPIRD office
  • Munglinup
Apothecia (circled in red) at the DPIRD’s Albany office sclerote depot.
Apothecia (circled in red) at the DPIRD’s Albany office sclerote depot. Photo courtesy of: Kithsiri Jayasena (DPIRD).

GRDC co-funded projects into epidemiology and decision support tools and lupin Sclerotinia, have sclerotia depots at eight locations in WA from Geraldton to Esperance.

Sclerotia have just started to germinate and produce apothecia in the depots at the Albany DPIRD office. No apothecia have been observed in any of the depots at the other locations yet.

Apothecia germinated from sclerotia.
Apothecia germinated from sclerotia. Photo courtesy of: Andrea Hills (DPIRD).

Plant pathologist Andrea Hills (DPIRD) found apothecia in a canola paddock near Munglinup.

These observations are a warning that the Sclerotinia disease cycle is commencing in the Albany and Esperance areas.

Cream coloured apothecia on the left, apricot coloured apothecia on the right.
Apothecia can range from cream (left) to apricot (right) in colour. Photos courtesy of: DPIRD staff Ciara Beard and Andrea Hills.

Apothecia are small cream-apricot coloured mushroom cups measuring up to 5mm in diameter that grow from sclerotia (the hard black fruiting bodies of sclerotinia) under cool (10-20°C), moist conditions. While they vary somewhat in colour, they all tend to darken over time and can survive for up to three weeks before withering away.

Apothecia growing from a sclerote
Apothecia growing from a sclerote. Photo courtesy of: Andrea Hills (DPIRD).

Carefully digging out the apothecia will usually show you its connection back to the sclerote it germinated from.

Apothecia release massive numbers of spores that cause sclerotinia stem rot by infecting petals in all broadleaf crops including canola, lupins, chickpeas, lentils, faba beans (rarely), lucerne and weeds (wild radish and cape weed). These infected petals fall into the crop canopy and under humid, damp conditions can cause stem infection.

Management

Growers in areas with a history of sclerotinia are reminded to consider sclerotinia management in their canola and lupin crops if they are close to or at flowering.

DPIRD research has shown that regular rainfall and high humidity (>75%) in the three weeks before and after commencement of flowering are most conducive for damaging levels of disease to occur in crops. While fungicide application reduces sclerotinia levels, it does not necessarily give a yield response, so it’s important to consider crop risk and value of disease management carefully each season.

Growers need to consider the following factors to determine their risk of sclerotinia and which paddocks to prioritise:

  • rotation history of the paddock
  • history of sclerotinia in the current paddock and those surrounding it
  • rainfall events before and after flowering
  • crop growth stage
  • dense crops with early canopy cover on loamy soil types are at higher risk.

The SclerotiniaCM decision support tool is available for use by canola growers during flowering to help determine the likely economic returns from applying fungicide at a specific time during flowering. The user can specify individual paddock data/history as well as recent and expected weather conditions so that the output relates to their own cropping circumstances. The SclerotiniaCM tool can be downloaded from the App Store or Google Play Store onto your iPad or Android tablet. This tool is not suitable for phones. For more information refer to DPIRD’s SclerotiniaCM decision support tool page.

Several fungicide products are registered for the control of Sclerotinia in canola while options in lupin are more limited. Fungicides need to be applied as recommended per product label. Strategic and responsible use of fungicides will reduce the risk of fungicide resistance developing. For more information refer to DPIRD’s Registered foliar fungicides for canola in WA and Registered foliar fungicides for lupin crops in WA.

Based on the extensive research conducted by DPIRD the following in-season sclerotinia management options are;

  • For canola:
    • Apply a single foliar application at 30-50% bloom, provided conditions are favourable for infection before and during flowering. See Table 1 below for recognising bloom stages in canola. Fungicides cannot be applied after 50% bloom (full bloom or when crop at its brightest). Use the SclerotiniaCM tool for guidance.
    • A second fungicide application at 50% bloom is generally only beneficial in seasons with an extended wet period. Use the SclerotiniaCM tool for guidance.
    • For lupin:
      • Aim to apply fungicide from full to late flowering on main spike in order to protect main stem pods and penetrate the lower canopy
      • A range of products are now registered in lupins which can reduce sclerotia canopy infection eg Veritas® Opti, Amistar® Xtra and Miravis® Star.
Table 1 Identification of bloom stages in canola (crop average):
Percent bloom Number of flowers open on the main stem
5% <5
10% 10
20% (petal drop commences) 11-14
30% 15-20
50% (full bloom, crop is at its brightest) >20

 

 

 

 

 

 

 

 

This season it is expected that blackleg risk, particularly upper canopy infection (UCI), will also be high. Fungicide applications for sclerotinia will confer a period of protection for UCI too (with an exception being procymidone applications). For more information on managing blackleg refer to DPIRD’s 2022 PestFacts WA Issue 5 article Blackleg and risk of sowing canola on canola and Managing blackleg in canola page.

Growers and consultants are encouraged to report to the PestFacts WA service any apothecia finds or disease observations as the season progresses.

Further information can be found at;

For more information on Sclerotinia contact plant pathologists Andrea Hills, Esperance on +61 (0)8 9083 1144, Ciara Beard, Geraldton on +61 (0)8 9956 8504 or Kylie Chambers, Northam on +61 (0)8 9690 2151.

 

 

Article authors: Ciara Beard (DPIRD Geraldton), Jean Galloway (DPIRD Northam) and Andrea Hills (DPIRD Esperance).