Insect Pest and Crop Degree Day Update – June 5, 2017

Ontario DD Map June 4Insect Degree Days

Weather Station Location Onion Maggot Seedcorn Maggot Cabbage Maggot Carrot Weevil Carrot Rust Fly Aster Leafhopper
(base 4°C) (base 4°C) (base 6°C) (base 7°C) (base 3°C) (base 9°C)
Harrow 613 613 467 400 690 283
Ridgetown 534 534 394 333 611 231
Delhi 519 519 380 321 593 220
Goderich 414 414 292 239 479 164
Guelph 396 396 278 227 463 149
Bradford*  438 438  318 266  501  178
Kemptville 409 409 302 254 471 175
Sudbury 261 261 179 146 314 91

Summary and IPM Update

Onion thrips have been seen on transplants in the Grand Bend area but at this point numbers are low.

Onion maggot flies have emerged and are active in most areas of the province. Current trap counts are low in the Holland Marsh area* and low to moderate in the Grand Bend area.

Cabbage maggot has reached the DD threshold for emergence in Harrow, Ridgetown, Delhi and Bradford. It is nearing the DD threshold in Goderich, Guelph and Kemptville.

The 2nd generation of seedcorn maggot flies have reached the DD threshold for emergence in Harrow. In most other areas of the province, we are just getting over the 1st generation or are currently between generations.

Carrot weevil adults are currently laying eggs, if they are present.

The 1st generation of carrot rust fly has begun to emerge in almost all areas of the province.

Most of the province (Ridgetown, Delhi, Goderich, Guelph, Bradford, Kemptville) have reached the DD threshold for overwintering Aster leafhopper eggs to hatch. Harrow is nearing adult emergence of the local population of Aster Leafhopper adults.

Use these thresholds as a guide, always confirm insect activity with actual field scouting and trap counts.

Below are the various insect DD thresholds for reference.

Thresholds

Degree Days
1st generation 2nd generation 3rd generation
Onion Maggot 210 1025 1772
Seedcorn Maggot 200 600 1000
Cabbage Maggot 314-398 847-960 1446-1604
Carrot Rust Fly 329 – 395 1399-1711 n/a
Carrot Weevil 138 – 156 Egg laying (oviposition) begins
455 90% of the egg-laying (oviposition) is complete
Aster Leafhopper 128 Overwintering eggs hatch
390 Local adult emergence

*Bradford weather, degree day data and information courtesy of the University of Guelph – Muck Crops Research Station

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