By: Dennis Van Dyk
Insect 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)|
Onion and seedcorn maggot flies have begun to emerge in most areas of the province except for Northern Ontario.
Cabbage maggot has reached the DD threshold for emergence in Harrow and is nearing the DD threshold in Ridgetown and Delhi.
Carrot weevil adults have reached the DD threshold to start laying eggs, if they are present.
The 1st generation of carrot rust fly has begun to emerge in almost all areas of the province.
The southern areas of the province (Harrow, Ridgetown and Delhi) have reached the DD threshold for overwintering Aster leafhopper eggs to hatch.
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.
|1st generation||2nd generation||3rd generation|
|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 and DD data courtesy of the University of Guelph – Muck Crops Research Station