Root, bulb, leafy and brassica vegetable pest report – 24 July 2012

The threshold for third generation emergence of onion maggot flies should be reached in Windsor in 5-6 days. Degree day accumulations indicate peak of third generation cabbage maggot in the Windsor area. The threshold for emergence of second generation carrot rust fly has been reached in all areas, except Wellington (likely in 2-3 days).

DOWNCAST, which helps predict downy mildew outbreaks in onions in the Holland Marsh, indicated that the risk of downy mildew on onions is moderate (depends on canopy size of crop). Risk may increase if temperatures cool and leaves remain wet for long periods. DOWNCAST is not available in other areas of Ontario, thus protective fungicides should be applied during cool, humid conditions. Currently, onion downy mildew has not been reported in Ontario.

Here are the degree days accumulated from April 1st until July 24th, 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*

1342.1

n/a

1457.8

n/a

24/07/2012

London

1412.1

1197.6

1524.9

1100.4

24/07/2012

Wellington

1239.4

1045.9

1343.9

955.6

24/07/2012

Windsor

1656.7

1430.8

1771.6

1321.6

24/07/2012

Thedford

1401

1192.5

1512.6

1094

24/07/2012

Delhi

1297.1

1097.3

1406.2

1008

24/07/2012

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*

624.5

878.2

1246.5

24/07/2012

London

661.4

919.8

1302.8

24/07/2012

Wellington

529.6

780.3

1139.9

24/07/2012

Windsor

836.3

1115.8

1542.9

24/07/2012

Thedford

653.3

911.5

1294.3

24/07/2012

Delhi

592.2

837.4

1193.1

24/07/2012

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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