Degree days for root, bulb and leafy vegetable pests – 4 July 2012

Thresholds for second generation emergence of onion maggot flies have been reached in the London area and is expected to be reached in Thedford, Delhi and Bradford/Holland Marsh over the next 2-4 days. Peak of second generation of cabbage maggot flies has been reached in London area. If resident populations are present, second generation of carrot rust fly adults should start emerging in the Windsor area.

Stemphylium leaf blight and purple blotch has been seen on onion in the Holland Marsh. These diseases are often found on leaves damaged by other diseases, insects or environmental stresses. Onion thrips counts are also increasing in the Holland Marsh. Keep an eye on aster leafhoppers. Over the past couple weeks, infectivity has been high in Michigan (ranging from 5.2—12.9%).

Here are the degree days accumulated from April 1st until July 4th, 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*

955.6

n/a

1045.2

728.5

03/07/2012

London

1021.1

846.6

1113.9

769.4

04/07/2012

Wellington

884.0

730.5

968.5

660.2

04/07/2012

Windsor

1213.7

1026

1303.8

937.8

03/07/2012

Thedford

937.2

776.7

1024.8

702.2

30/06/2012

Delhi

871.5

715.7

958.6

648.4

28/06/2012

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*

400.9

591.7

875.5

03/07/2012

London

430.4

628.8

931.8

04/07/2012

Wellington

334.2

524.9

804.5

04/07/2012

Windsor

557.5

774

1117.1

03/07/2012

Thedford

381.5

567.7

854.5

30/06/2012

Delhi

342.6

521.8

789.5

28/06/2012

Ridgetown

Data not updated since 28 May 2012


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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