Cole Crops, Root, Bulb and Leafy Vegetable Edition by
Jennifer Allen, Vegetable Crop Specialist, OMAFRA, Guelph 

Carrot Diseases
Funding Opportunity
Harrow Open House
Degree Days
Disease Forecasting

Carrot Diseases

There are three organisms that cause leaf blight in carrots, Cercospora carotae, Alternaria dauci and Xanthomoas campestris.   Both C. carotae  and A. dauci are fungi while X. campestris is a bacterial pathogen.

Cercospora leaf blight, requires a minimum of 12 hours of leaf wetness and temperatures between 20-30ºC to develop. Under optimal conditions, lesions can be observed as early as 3 days after inoculation; however, under average conditions lesions are generally observed 10 days after inoculation. This disease is characterized by circular brown/black lesions on leaves and petioles surrounded by a yellowish area with no distinct border.  

 B. Elliot and P. Northover, 2008

Alternaria leaf blight typically occurs later in the season and is characterized by dark brown to black lesions with irregularly shaped yellow halos.  This disease favours temperatures from 8-28ºC with optimal production between 20-30ºC. It is spread by running and splashing rain, wind and farm equipment. Symptoms appear 8 to 16 days after inoculation. 

Bacterial leaf blight is caused by a bacteria, X. campestris p.v. carotae, and is spread by rain drops, irrigation water, insects and farm equipment. The bacteria are present on plants, growing epiphytically until the population reaches a critical density and optimal conditions (i.e. 25-30ºC and leaf wetness) occur. Disease symptoms appear 10 to 12 days after inoculation. It is often very difficult to differentiate amongst these three diseases.  

Monitoring and Control

Fungicides are necessary once blight is detected on 1-2% of the leaf area examined. To determine the percentage of leaf area infected, randomly sample 50-100 mid-age leaves. A leaf is considered infected if one or more lesions are observed. If blight is present on 13 of 50 or 25 of 100 leaves/leaflets examined, a fungicide spray should be applied before the next forecasted rainfall, or before the next night when the forecasted temperature is 16°C or higher. 

Farm Innovation Program Supports Commercialization of Innovative Research 

Quicker access to new farm technology for Ontario farmers and producers will help them be more responsive to changing market demands and increase their competitiveness. 

The Growing Forward Farm Innovation Program will provide funding for research and testing on new technology used on farms. The program is open to:

• Commodity organizations that are not supply managed         
• Farmers partnering with any commodity organizations.

Applications (www.adaptcouncil.org/index.php) for this year’s grants are now open.

Quotes

“The Government of Canada puts farmers first by funding innovation that will provide new growth for their businesses. Growing Forward will help farmers get new ideas off the ground and into the field.”    

– Daryl Kramp, Member of Parliament for Prince Edward-Hastings), on behalf of Federal Agriculture Minister Gerry Ritz

 “Ontario’s producers can take advantage of the latest technologies to improve their competitiveness and respond more quickly to new market opportunities.”  

 – Leona Dombrowsky, Minister of Agriculture, Food and Rural Affairs 

Quick Facts

The Farm Innovation Program is part of the Innovation and Science Suite of programs under Growing Forward, a federal-provincial-territorial initiative that runs until 2013.

• More than $12.5 million is available under the Farm Innovation Program, which is delivered by the Agricultural Adaptation Council.        
• The Growing Forward agreement commits $1.3 billion in government funding for non-business risk management (non-BRM) cost-shared programs across the country. 

Learn More

About Growing Forward in Ontario
www.omafra.gov.on.ca/english/about/growingforward/index.htm

About the Agricultural Adaptation Council
www.adaptcouncil.org/

About the Premier’s Awards for Agri-Food Innovation 
www.omafra.gov.on.ca/english/premier_award/index.html

Harrow Open House

Degree Days

Here are the degree and growing degree-day accumulations for April 1 – July 31, 2009. Yellow highlights areas where 2nd generation accumulations have been reached.

Area	Onion Maggot	Cabbage Maggot	Carrot Rust Fly	Carrot Weevil	Tarnished  Plant Bug	Leaf-hopper	GDD
Bradford/ Holland Marsh*	1345.5	n/a	1472	974.7	457.5	752.5	1219
Sarnia	1405.9	1162.2	1532.1	1045.9	537.4	826.4	1281
London	1457.4	1207.1	1585.9	1086.3	549.7	858.3	1307
Waterloo	1308.8	1065.7	1435.1	950.3	441.6	735.0	1188
Windsor	1766.6	1508.8	1898.5	1383.8	800.8	1142.7	1638

Degree-day information for pests.

	Degree Days
	1st Generation	2nd Generation	3rd Generation
Onion Maggot	210	1025	1772
Cabbage Maggot	314-398	847-960	1446-1604
Carrot Rust Fly	329 – 395	1399-1711	n/a
Carrot Weevil	138 – 156 455 (90% oviposition)	No model available	n/a
Tarnished Plant Bug	40	n/a	n/a
Aster Leafhopper	128	390	n/a

Disease Forecasts

BOTCAST — Disease severity index is 57.  Risk of developing Botrytis is moderate to high.  Monitor fields regularly and if field has more than 1 lesion/leaf, apply a recommended fungicide.        

DOWNCAST—Predicted sporulation infection period for the last three days.  Risk of downy mildew on onions is high.  Downy mildew has been found in onions in the Holland Marsh.

BREMCAST—Predicted sporulation infection period in the last three days.  Risk of downy mildew on lettuce is moderate to high.  

Data provided thanks to funding from the Holland Marsh Growers’ Association, Bradford Co-op Storage Ltd., Muck Crops Research Station, Department of Plant Agriculture, University of Guelph., Lake Simcoe Conservation Authority, Bayer CropScience, BASF, DuPont, Engage Agro and Syngenta.