Degree days for root, bulb and leafy vegetable pests – 22 May 2012

Thresholds for onion maggot fly emergence have been reached for all areas degree days have been calculated for (Bradford/Holland Marsh, London, Wellington, Windsor, Thedford, Delhi and Ridgetown). First generation adults of cabbage maggot should start to appear in the Windsor area. For other areas, except Wellington, cabbage maggot adults should start to appear in 5-7 days. If resident populations are present, carrot rust fly adults have begun to emerge in Bradford/Holland Marsh, London, Thedford, Delhi and Ridgetown areas. The threshold for carrot rust fly emergence should be reached in 1-2 days for the Wellington area. If resident populations are present, carrot weevil have likely started to lay eggs in all areas. Based on degree days, Tarnished plant bug should have started to emerge in all areas. Overwintering leafhopper eggs have likely started to hatch in all areas, except Wellington.

Here are the degree days accumulated from April 1st until May 22nd, 2012.

Area

Onion Maggot

Cabbage Maggot

Carrot Rust Fly

Carrot Weevil

As of

Bradford/Holland Marsh*

284.9

n/a

332.4

183.7

22/05/2012

London

325

236.5

374.8

202.3

22/05/2012

Wellington

256.9

189.4

298.4

162.1

22/05/2012

Windsor

439.5

339.6

491.4

292.3

22/05/2012

Thedford

317.8

235.3

366.4

199.8

22/05/2012

Delhi

306.3

224.5

356.4

194.2

22/05/2012

Ridgetown

335.5

251.7

384.5

216.2

22/05/2012

Area

Tarnished Plant Bug

Leafhopper

GDD

As of

Bradford/Holland Marsh*

66.2

130.9

247.1

22/05/2012

London

78.3

147.7

278.7

22/05/2012

Wellington

50.1

112.8

220.4

22/05/2012

Windsor

123.1

213.6

388.7

22/05/2012

Thedford

74.1

143.3

274.1

22/05/2012

Delhi

73.4

141.6

261.3

22/05/2012

Ridgetown

83

156.6

290.4

22/05/2012

* Data provided thanks to Muck Crops Research Station, Department of Plant Agriculture, University of Guelph

 

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 (overwintering egg hatch)

390 (local adult emergence)

n/a

n/a


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