VCR – Vegetable Crop Report – May 9th, 2024

Crop Updates

Brassica crops – Transplanting continues. Seedcorn maggot fly is likely active in Essex, Chatham-Kent and Lambton counties. Dig up wilted transplants and inspect roots for insect damage. 2023 was the last year to use Lorsban / chlorpyrifos products for maggot management. Success (Group 5) and Verimark (Group 28) are registered as greenhouse tray drenches and Verimark can also be used as an in-furrow application in the transplant water at the time of transplanting. Be on the lookout for flea beetle emergence as the soil temperature reaches above 10°C. The 2024 Brassica Crops IPM Scout Training workshop will be held on Monday, May 13^th. Register for the virtual or in-person workshop here or by calling 1-877-434-1300.

Carrots – If you have carrot weevil in your area, get those weevil traps out this week as overwintering adults will be emerging in the next week or so.

Garlic – Plants are at an average of 4-8 leaves. Leek moth is active where there are established populations. Seedcorn maggot fly damage has been observed in multiple fields in SW Ontario and has reached its first-generation threshold in Essex, Chatham-Kent, Norfolk, Huron, Durham, Middlesex and Lambton counties. Dig up plants that have wilted leaves to look for seedcorn maggot larvae, wireworms or millipedes.

Onions – Transplanting is underway across the province and many fields have been direct seeded in drier areas. Fields that were planted in early April have reached the second true leaf. The threshold for seedcorn and onion maggot fly have been reached in Essex, Chatham-Kent, Norfolk, Huron, Durham, Middlesex and Lambton counties. Pay attention to crop debris left over from last year, bury cull piles, and manage volunteer onions. Conditions have been favourable for downy mildew development this spring. Downy mildew was found on onion plants that overwintered in a community garden in Guelph on May 8^th, 2024 (Figures 1-2). If you were unable to attend the Onion IPM scouting workshop today, a recorded version can be found at: https://www.youtube.com/watch?v=OwGISdtuNEU

Onion leaves with fuzzy velvety growth of downy mildew. — Figure 1. Downy mildew found on onions in a community garden in Guelph May 8th, 2024.

Sporangiophore and spores (sporangia) of onion downy mildew from onions in a community garden in Guelph May 8th, 2024. — **Figure 2**. Sporangiophore and spores (sporangia) of onion downy mildew from onions in a community garden in Guelph May 8^th, 2024.

Potatoes – Have some wet, slimy, rotten potatoes or seeing blackleg show up in the field? We want them. We’re surveying soft rot bacteria this year to see what species Ontario growers are dealing with. Please see the article here for more details or contact Dennis (519-766-5337, dennis.vandyk@ontario.ca) to arrange pick-up of samples. Planting continues in-between rain events. Late blight incidence last season means the risk for early season infection is higher this year. Take special care to kill volunteers and get rid of any cull piles. Consider a late blight seed treatment if you’ve seen any late blight incidence on seed. You can find a list of registered seed treatments for late blight here.

Pest Degree Day Forecasting

County	Carrot Rust Fly	Onion Maggot	Carrot Weevil	Aster Leafhopper	Tarnished Plant Bug	Cabbage Maggot	Seedcorn Maggot	European Corn Borer
THRESHOLD	329-395, 1399-1711	210-700, 1025-1515	138-156, 455+	128+	40+	314-398, 847-960, 1446-1604	200-350, 600-750, 1000-1150	See legend below
Bruce***	233	189	94	52	17	120	189	38
Essex*	415	359	219	151	70	261	359	122
Chatham-Kent*	355	304	178	120	49	214	304	93
Norfolk**	344	291	158	99	36	197	291	74
Huron***	287	238	122	70	27	156	238	50
Wellington Centre**	255	206	101	55	11	129	206	36
Wellington North**	247	201	98	56	16	128	201	39
Simcoe***	244	199	96	49	9	124	199	30
Durham***	273	223	109	58	15	142	223	39
Peterborough	247	200	96	48	12	126	200	33
Kemptville***	253	205	107	62	20	133	205	45
Sudbury***	140	109	48	24	4	64	109	15
Timiskaming***	124	99	46	25	4	60	99	16
Lambton**	339	290	165	106	45	202	290	82
Thunder Bay	95	69	19	7	0	30	69	3
Middlesex**	352	299	169	109	45	208	299	84
Renfrew	241	195	98	59	21	124	195	44