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NY9406 Downy Mildew on seedlings - factsheet
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Phytochemical composition of food
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Summer Root Rot in Parsley
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Vegetable Disease Program
Vegetable Diseases in Australia
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VG00013 Leek Diseases
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VG00026 IPM Eggplant & Cucumber
VG00031 Peas - downy mildew & collar rot
VG00031 Peas - Downy Mildew - metalaxyl resistance
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VG00044 Clubroot - Applicator design
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VG00044 Clubroot - Nutritional amendments
VG00044 Clubroot - Strategic application
VG00044 Clubroot – Introduction
VG00044 Clubroot – Limes and liming
VG00044 Clubroot – Prevention & Hygiene
VG00044 Clubroot – Understanding Risk
VG00044 Total Clubroot Management
VG00048 Alternate fungicides for sclerotinia control
VG00048 Brassica green manure conference paper 2004
VG00048 Brassica Green Manure Update 16
VG00048 Brassica Green Manure Update 18
VG00048 Diallyl Disulphide - DADS - trials
VG00048 Lettuce - Sclerotinia biocontrol
VG00048 Lettuce Sclerotina - Biocontrols
VG00058 Pea - Collar Rot
VG00069 Cucumber & Capsicum diseases
VG00084 Beetroot for Processing
VG01045 Bunching Vegetables - disease control
VG01049 Compost - Benefits
VG01049 Compost - Choosing a Supplier
VG01049 Compost - Getting Started
VG01049 Compost - Introduction
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VG01049 Safe Use of Poultry Litter
VG01082 Broccoli Adjuvant Poster
VG01082 Broccoli Head Rot
VG01096 Article - White Rot research
VG01096 Integrated Control of Onion White Rot
VG01096 Poster - Alternative fungicides
VG01096 Poster - Diallyl Disulphide - DADS
VG01096 Poster - Trichoderma biocontrol
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VG01096 White Rot - Spring Onions
VG02020 Capsicum - Sudden Wilt
VG02035 Capsicum - virus resistance
VG02105 Vegetable Seed Dressing Review
VG02118 White Blister
VG03003 Lettuce - Varnish Spot
VG03092 Lettuce - Shelf Life
VG03100 Retailing Vegetables - Broccolini®
VG04010 Maximising returns from water
VG04012 Hydroponic lettuce - root rot
VG04013 Brassica White Blister
VG04013 White Blister - Control Strategies
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VG04013 White Blister - Workshop Notes
VG04014 Better Brassica
VG04014 better brassica - roadshow model
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VG04014 Clubroot Guidebook
VG04014 Clubroot Poster
VG04015 Benchmarking water use
VG04016 Celery leaf blight - Poster
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VG04019 Nitrate & Nitrite in Leafy Veg
VG04021 Vegetable Seed Treatment
VG04025 Parsley Root Rot
VG04059 Diagnostic test kits
VG04061 White Blister - alternative controls
VG04061 White Blister - Workshop 2007
VG04062 Beetroot Study Tour
VG04067 IPM - Lettuce Aphid
VG05007 Onion White Rot - post plant fungicides
VG05008 IPM - Cultural Controls
VG05014 IPM - Native vegetation pt1
VG05044 IPM - Consultants Survey
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VG05044 IPM - Lettuce Aphid Trials
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VG05044 IPM - Project Summary
VG05045 Parsnip Canker
VG05051 Climate Change
VG05053 Rhubarb Viruses
VG05068 Baby Leaf Salad Crops
VG05073 Mechanical Harvesting
VG05090 Green Bean - Sclerotinia
VG05090 Rhizoctonia Groups
VG06014 Revegetation for thrip control
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VG06046 Parsley Root Rot
VG06047 Celery - Septoria Predictive Model
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VG06092 Pathogens - Gap Analysis
VG06092 Pathogens of Importance - poster
VG06140 Beetroot - colour quality
VG07010 Systemic aquired resistance
VG07015 Curcubit field guide
VG07070 Conference Notes 2008
VG07070 Foliar diseases
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VG07070 Predicting Downy Mildew on Lettuce
VG07070 White Blister - Chinese Cabbage
VG07070 White Blister - Cultural Controls
VG07070 Workshop Notes - 2008
VG07070 Workshop Notes - 2010
VG07125 IPM - soilborne diseases
VG07126 Biofumigation oils for white rot
VG07126 New approaches to sclerotina
VG07127 White Blister - Alternative Controls
VG08020 Optimising water & nutrient use
VG08026 Pythium - field day
VG08026 Pythium - workshop 2010
VG08026 Pythium control strategies - overview
VG08107 - Carbon Footprint - workshop
VG08107 - Carbon Footprint part 1 - definitions
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VG08107 - Carbon Footprint part 3 - calculators
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VG08107 - Carbon Footprint part 5 - users
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VG08426 Parsnip - Pythium Notes 2010
VG09086 Evaluation of Vegetable Washing
VG09159 Grower Study Tour- Spring Onions & Radish
VG96015 Carrot Crown Rot
VG96015 Carrot Defects - Poster
VG97042 Export - Burdock, Daikon and Shallots
VG97051 Pea - ascochyta rot
VG97064 Greenhouse Tomato and Capsicum
VG97084 Green Bean - white rot
VG97103 Celery Mosaic Virus
VG98011 Carrot - Cavity Spot
VG98048 Lettuce - Adapting to Change
VG98083 Lettuce - rots & browning
VG98085 GM Brassicas
VG98093 Microbial hazards - review
VG98093 Safe vegetable production
VG99005 Quality wash water
VG99008 Clubroot - rapid test
VG99016 Compost and Vegetable Production
VG99030 Globe Artichokes - value adding
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VG99057 Soil Health Indicators
VG99070 IPM - Celery
Victorian soil health
VN05010 Folicur - alternative carriers
VN05010 Onion White Rot - Fungicides
VN05010 Onion White Rot - summary
VX00012 Metalaxyl breakdown
VX99004 Clean & Safe Fresh Vegetables
Whitefly & Viruses
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VG98011 Carrot - Cavity Spot

Cavity spot is a serious disease of carrots that has the potential to severely reduce marketable yield.

A survey of Western Australian carrot crops, showed that cavity spot was present in almost half of 200 crops.

World wide, cavity spot is caused by two species of Pythium, P. violae and P. sulcatum.

These are soil-borne fungi that build up on sites that have been repeatedly cropped to carrots. P. sulcatum was identified as the cause of cavity spot in Western Australia.

Other Pythium diseases of carrots include damping off, resulting in low root numbers at harvest, and root dieback, resulting in forked and misshapen carrots.

This report covers research into the causes of cavity spot and related diseases in carrot production areas in Australia, together with information on integrated disease control.

Authors
Elaine Davidson Allan McKay

VG98011 Integrated management of Pythium diseases of carrots - 2001
Download 978kb

Summary :

  • The cause of cavity spot and other Pythium diseases of carrots in Australia Cavity spot disease of carrots is caused by Pythium spp.

  • P. violae and P. sulcatum are the most important causes of cavity spot worldwide. P. sulcatum, but not P. violae, causes this disease in Western Australia.

  • A survey of Pythium spp. associated with carrot crops in eastern and southern Australia showed that P. sulcatum was the most widespread pathogenic species, occurring in all States and most regions.

  • P. violae was recovered from the River Murray basin in Victoria and South Australia. This is the first record of P. violae from carrots in Australia

  • The diversity of P. sulcatum isolates, as shown by DNA analysis, suggests that it is a cosmopolitan species that may occur on native Australian Apiaceae.

Cultural methods for controlling cavity spot

   Host range and rotation :

The major hosts of Pythium sulcatum are members of the carrot family (Apiaceae).

Grasses (barley, maize, oats, rye and wheat) used for wind protection, and un-related vegetables, are not infected.

There was a significant reduction in the incidence and severity of seedling infection by P. sulcatum when carrots followed broccoli.

Oospores of P. sulcatum are able to survive for at least 21 months in the absence of a host.

   Solarisation :

Solarisation is a cultural method for controlling soil-borne diseases where soil is heated by solar energy, usually under black plastic.

In the field it is unlikely that temperatures achieved by solarisation will be high enough to reduce the inoculum potential of P. sulcatum, although these temperatures may be sufficient to reduce the inoculum of P. violae.

   Chemical methods for controlling cavity spot :

In a field experiment on a badly infested site, cavity spot control was attempted with a number of commercially available chemical and microbial formulations.

Seedling harvests showed that Pythium infection was only reduced in the metalaxyl treatment.

At the final harvest there was no significant reduction in the incidence or severity of cavity spot in any treatment although Amistar® is worthy of further work.

A survey was carried out to determine whether there was evidence of enhanced breakdown of the fungicide metalaxyl on sites where it has been used in the past.

The half-life varied from less than 1 day to 43 days, compared with a published value of 70 days. Enhanced breakdown of metalaxyl appears to be a widespread problem.

   Varietal tolerance to cavity spot

Identification of carrot varieties tolerant to cavity spot, that are also suitable for export production, is an important part of integrated disease control.

Many of the most cavity spot tolerant varieties identified did not produce the high root quality demanded by export markets.

Acknowledgements :

We thank carrot growers for allowing access to their properties, especially Luis Gazzola and George Parente for hosting the farm trials.

We thank Robyn Brett (Agriculture Victoria, Knoxfield), Robin Cole (South Australian Research and Development Institute, Adelaide), Sally-Ann Henderson (Agriculture Victoria, Irymple Research Station), Hoong Pung (Serve-Ag Research, Devonport, Tasmania), Rob O'Brien (Queensland Department of Primary Industry, Indooroopilly) and Len Tesoriero (New South Wales Agriculture, Camden) for providing Pythium cultures from the different carrot growing regions of Australia.

We thank Giles Hardy (Murdoch University, Western Australia) and Geoff White (Horticulture Research International, UK) for providing authenticated cultures of P. sulcatum and P. violae.

We thank J. Speijers for statistical advice.

We thank the following companies for the gift of chemical and biological agents and recommendations for their use:

  • Crop Care Australasia Pty Ltd for the gift of Amistar® WG

  • Novartis Crop Protection Australasia Pty Limited for the gift of Bion® 50 WG

  • E-2001 W.A. for the gift of E-2001®

  • EM Distributors WA for the gift of EM microbes®

  • Lefroy Valley for the gift of Trichoflow™-T

We thank Paul Murphy, Rob Deyl, Tony Shimmin and Rohan Prince for technical assistance in Western Australia and D. Wells for assisting with assessing one of the trials in Victoria.

Staff at Medina Research Station, especially Gavin D'adhemar, are thanked for managing the experiments and assisting with harvest and grading.

We thank the Chemistry Centre (WA) for carrying out metalaxyl analyses on soil samples.

This project was funded by the Department of Agriculture, Western Australia and Horticulture Australia Ltd through the National Vegetable R&D Levy .

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


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