Root, bulb, leafy and brassica vegetable pest report – 21 August 2012

The threshold for third generation emergence of onion maggot flies has been reached in Delhi and Bradford/Holland Marsh and should be reached in 10-12 days in Wellington (previously reached in WindsorLondon and Thedford). Over the past week, onion thrips counts have been increasing in some onion fields, as reported by the Muck Crops Research Station.  From earlier this week, DOWNCAST indicated that the risk of downy mildew on onions was moderate to high; however, it has dropped to moderate as the week progresse. No downy mildew cases have been reported. DOWNCAST is not available in other areas of Ontario, thus protective fungicides should be applied during cool, humid conditions.

As previously mentioned, the threshold for emergence of second generation carrot rust fly has been reached in all areas. Earlier this week, carrot rust fly activity was still high in some areas of the Holland Marsh, especially in more sheltered areas. Carrot rust fly activity has slowed down as the week progresses.

Degree day accumulations indicate peak of third generation cabbage maggot in Delhi, London and Thedford (in 4-5 days for Wellington).  Please let me know if you are seeing Swede Midge damage this season. Contact Marion Paibomesai at marion.paibomesai@ontario.ca, 519-826-4963.

Here are the degree days accumulated from April 1st until August 21st, 2012.

(These values are provided as guidelines only. Local environments, soil type, field history, etc. may influence activity of these pests.)

Area

Onion Maggot (base 4)

Cabbage Maggot (base 6)

Carrot Rust Fly (base 3)

Carrot Weevil (base 7)

As of

Bradford/Holland Marsh*

1804.8

n/a

1943.5

n/a

21/08/2012

London

1875.5

1605

2016.3

1479.8

21/08/2012

Wellington

1655.3

1405.8

1787.8

1287.5

21/08/2012

Windsor

2159.0

1877.1

2301.9

1739.9

21/08/2012

Thedford

1876.4

1611.9

2016

1485.4

21/08/2012

Delhi

1755.5

1499.7

1892.6

1382.4

21/08/2012

Ridgetown

Data not updated since 28 May 2012

 

Area

Tarnished Plant Bug (base 12)

Leafhopper (base 9)

GDD (base 5)

As of

Bradford/Holland Marsh*

858.2

1195.9

1676.2

21/08/2012

London

900.8

1243.2

1738.2

21/08/2012

Wellington

721.5

1056.2

1527.8

21/08/2012

Windsor

1114.6

1478.1

2017.2

21/08/2012

Thedford

904.7

1246.9

1741.7

21/08/2012

Delhi

826.6

1155.8

1623.5

21/08/2012

Ridgetown

Data not updated since 28 May 2012

*Data provided by Muck Crops Research Station, University of Guelph.

Degree day model 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 (overwintering egg hatch)

390 (local adult emergence)

n/a

n/a

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