VG00058 Pea – Collar Rot

Ascochyta (Mycosphaerella pinodes) is a fungus that occurs in processing pea crops.

The processing pea industry is highly competitive with imports from New Zealand placing economic pressure on producers to continually improve their management practices to remain viable against cheaper imported product.

The production areas of Tasmania and southwest Western Australia are further disadvantaged by having a growing season confined to winter and spring rather than the usual spring and summer season found overseas.

These growing conditions provide a very high incidence of the Ascochyta fungus (Mycosphaerella pinodes), particularly in Western Australia.

Conventional treatments for the control of Ascochyta in processing peas have predominantly focussed on chemical and seed treatments. These treatments have demonstrated only minor success in controlling the fungus.

The objectives of this project were to identify the reasons Ascochyta fungus appears and whether its incidence can be minimised with the use of chemical and nonchemical treatments or cultural practices.


Author

Lloyd Williams

VG00058 Increasing the competitiveness of the Australian processing pea industry through minimising the economic impact of collar rot disease (Ascochyta) - 2004
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Summary :

Minimising the incidence of Ascochyta through the reduction of herbicide applications

Field trials were conducted over a three-year period to assess the effect of a number of broadleaf herbicides to minimise the number of applications required to control weeds through the life of the pea crop. With a reduction in the number of herbicide applications, the incidence of Ascochyta would be lower as minimal physical damage to the vines would occur.

The trials demonstrated that Command and Frontier Optima:

  • in combination these pre-emergent herbicides were the most effective treatment in the trials and had the longest activity spectrum of all of the herbicides
  • as a single pre-emergent spray can suffice against broadleaf weed emergence.
  • Bladex herbicide halved the number of herbicide sprays to a single application.

The relationship between soil compaction & Ascochyta

Field trials were conducted over two years (2001 & 2003) to measure the degree of soil compaction in pea crops in those areas of contact with farm machinery and in areas with no contact.

Farmers observed that areas of high soil compaction displayed high levels of Ascochyta activity that resulted in poor yield.

Methods of removing and reducing soil compaction and the resulting Ascochyta infection were investigated.

  • The research demonstrated that farm machinery caused compaction of the soil and damaged the crop resulting in potential yield losses of up to 25%.
  • The introduction of permanent roadways resulted in no damage to pea vines and reduced the risk of Ascochyta infection.
  • Crop trash may have a buffering potential against the incidence of compaction in both the roadways, tramways and within the commercial crop.

The effectiveness of fungicides in controlling Ascochyta

  • Bravo 720 was the only fungicide to show any preventative effect against Ascochyta.
  • Bravo 720 remains the sole preventative measure against the Ascochyta fungus.

Sap composition of pea vines

  • There was no significant relationship between sap composition of pea vines sampled and their sample sites.
  • There was no clear link between pea vine sap levels and the incidence of Ascochyta in the pea vine samples.

Aerial Photography

  • The plant cell density image demonstrated that the crop was far from uniform. It also showed that less than 50% of the crop was at a maximum density.
  • The true image showed the machinery paths.
  • The false image demonstrates that approximately 20% of the crop contains an optimum density of healthy plant cells in their leaves and the remainder of the crop contains a much lower density.
  • The vigour image shows that up to 50% of the crop is unhealthy.

Acknowledgements :

Input from many farmers over the three years from Kendenup pea growers and continuous support from the committee members is greatly appreciated.

Warren Lee from Vital Food Pty Ltd for your continuous assistance is thanked.

Thank you to the staff of Serve-Ag Research for your assistance and co-operation.

Project funding is by Vital Food Pty Ltd, the Kendenup Pea Growers Association and Horticulture Australia is acknowledged.

The Australian Government provides matched funding for all HAL’s R&D activities.

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