Category Archives: Onions

Tracking the march of leek moth in Ontario

Leek moth (Acrolepiopsis assectella) is an invasive pest of European and Asian origin. The first North American detection occurred near the National Capitol Region (Ottawa) in 1993.  Since then, the leek moth has spread Continue reading Tracking the march of leek moth in Ontario

Spray Coverage in Carrot Potato and Onion

Jason Deveau, Application Technology Specialist – OMAFRA;
Dennis Van Dyk, Vegetable Crop Specialist – OMAFRA

In recent years, Syngenta has been promoting the Defy 3D nozzle in the UK, which is a 100° flat fan, designed to run alternating 38° forward or backward along the boom. They prescribe a boom height of 50 to 75 cm, 30-40 psi, and travel speeds of 10 to 14 km/h in cereals and vegetables. Compared to a conventional flat fan, they claim that the angle and medium-coarse droplets promise less drift and improved coverage.

In 2017, Hypro and John Deere began distributing the Defy 3D in North America. Our goal was to explore coverage from the 3D in vegetable crops. We compared the nozzle’s performance to common grower practices in onion, potato and carrot in the Holland Marsh area of Ontario.

Marsh

Continue reading Spray Coverage in Carrot Potato and Onion

Disease and Insect Update – July 13, 2017

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)
Harrow 1265 1265 1044 938 1380 746
Ridgetown 1153 1153 937 838 1268 660
Delhi 1125 1125 910 813 1237 636
Goderich 973 973 775 684 1076 533
Guelph 928 928 735 646 1034 492
Bradford* 987 987 795 708 1086 547
Kemptville 969 969 786 700 1069 544
Sudbury 754 754 597 525 845 394

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

Summary

Cabbage, onion and seedcorn maggot fly activity should be beginning to increase from Norfolk across to Lambton and south. Most of the province is in-between generations currently but should start seeing the next generation emerge in the next few weeks depending on weather.

For carrot weevil we are now well past the degree day threshold for 90% oviposition across the province. This year we will be monitoring for the presence of a possible 2nd generation of carrot weevils. If you think you are having late season carrot weevil issues, please contact Dennis (dennis.vandyk@ontario.ca).

We have reached the DD threshold for carrot rust fly in Harrow only. The rest of the province should be between generations currently.

Aster leafhoppers adults are now present across the province.

Disease Forecasting

Onion Downy Mildew (DOWNCAST disease forecasting model):
In Bradford, conditions have not been conducive to sporulation so risk of downy mildew is low to moderate.
In Lambton county, sporulation infection periods (SIP) have been accumulated from July 2-5 and then again on July 12 meaning conditions and risk is high in transplant onions and moderate to high in seeded onions.

Late Blight:
Late blight DSVs are accumulating quickly in most areas of the province.
Late blight on potatoes has been confirmed in the Simcoe/Durham county region but the risk remains high across the province. Growers should be applying late blight specific fungicides along with a broad-spectrum fungicide like chlorothalonil (Bravo, Echo), metiram (Polyram) or mancozeb (Manzate, Penncozeb, Dithane).

Check OnPotatoes for up to date late blight risk information and USAblight for currently reported late blight incidence in the Great Lakes region.

Crop Updates

Onions: Earliest direct seeded onions have six true leaves while the majority are at the four to five leaf stage. Stemphylium leaf blight, purple blotch, onion smut and Botrytis leaf blight has been detected in Ontario. See the Stemphylium leaf blight article in a previous OnVegetables post for more information.

Garlic: Leaf dieback has been seen in multiple areas with Fusarium basal rot and bulb and stem nematode. Carefully inspect the basal plate and look for fungal growth or rot on the stem. For confirmation, send suspect cloves to a certified pest diagnostic clinic for bulb and stem nematode extraction. Leek moth has been identified in pockets of Southwestern Ontario.

Brassica: Cabbage maggot is active and severely infested plants may wilt in hot weather. Wilt can also be caused by clubroot, a soil-borne pathogen infecting the roots and causing club-like symptoms. A clubroot survey is underway; please contact travis.cranmer@ontario.ca for more information if you find clubroot in your field. Swede midge has also been reported throughout Southwestern Ontario and is affecting the meristems later seeding dates of multiple brassica crops. Continue to scout for flea beetles, diamondback moth, cabbageworm, aphids, thrips and tarnished plant bugs.

Celery: Tarnished plant bugs have been detected in Thedford and the Holland Marsh. Scout for damage from carrot weevils laying eggs.

Below are the various insect DD thresholds for reference.

Thresholds

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

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

Ontario DD Map July 13

Scouting for onion thrips

Onion thrips (Thrips tabaci) feed on more than just onions; they also feed on cabbage, leaf lettuce, a variety of other vegetables and fruits, field crops, and many weed species. Thrips are unique from other insects as they have rasping-sucking mouthparts that allow them to scratch the cell walls of leaves, suck up the cell contents including the chlorophyll, and leave behind a shiny, translucent trail on the leaf. A single female can produce Continue reading Scouting for onion thrips

Stemphylium is the new Botrytis

Stemphylium leaf blight (Stemphylium vesicarium) of onion starts as yellow-tan, water-soaked lesions developing into elongated spots. As these spots cover the entire leaves, onions prematurely defoliate thereby reducing the yield and causing the crop to be more susceptible to other pathogens. Stemphylium was first identified in Ontario in 2008 and has since spread throughout the Holland Marsh and other onion growing areas in southwestern Ontario.

Stemphylium leaf blight can sometimes be misdiagnosed as Continue reading Stemphylium is the new Botrytis

Insect Pest and Crop Degree Day Update – June 13, 2017

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)
Harrow 716 716 556 481 800 351
Ridgetown 629 629 474 407 712 290
Delhi 618 618 464 399 700 284
Goderich 500 500 365 305 573 215
Guelph 463 463 332 274 538 182
Bradford* 523 523 388 329 593 227
Kemptville 502 502 381 326 571 232
Sudbury 353 353 257 216 412 147

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

Summary

Onion maggot flies are active in most areas of the province.

Cabbage maggot has reached the DD threshold for emergence in all areas of the province except up North.

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. In Harrow we have past the degree day threshold for 90% oviposition. This means if carrot weevils are present then almost all of the egg-laying has been completed.

The 1st generation of carrot rust fly is emerging or has emerged in the province.

All areas of the province 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.

IPM Update

Onion: Earliest direct seeded onions are at the fifth leaf stage while the majority are the third leaf stage. There is a low risk for Botrytis leaf blight. When scouting, check the underside of the outer leaves and look for small, light green to yellow lesions surrounded by white halos. Herbicide injury will be often more white than green but can be mistaken for Botrytis leaf blight. Thrips have been detected in most onion growing areas; pull the leaves apart and look down into the leaf base for 2mm-long grey adults or very small yellow nymphs ~1mm in length. Onion fields next to hay or overwintering rye are at a greater risk as thrips move once the hay or rye is cut.

Garlic: Continue to scout for symptoms of rot in the basal plate which may be due to bulb and stem nematode, Fusarium basal rot or white rot. Look for plants that have yellowing of foliage or tip dieback and dig carefully around the plant and look for fungal growth or rot on the stem. Onion thrips and onion maggot flies have been detected.

Brassica: First generation of cabbage maggots are active. Continue to scout for diamondback moth, cabbageworm, aphids, thrips and tarnished plant bugs. 

Celery: Scout for tarnished plant bugs as they are emerging and are typical found first around field borders.

 

Ontario DD Map June 11 2017

 

Below are the various insect DD thresholds for reference.

Thresholds

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

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

 

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