VCR – Vegetable Crop Report – May 29th, 2025

Welcome back to the next VCR of 2025!

Due to the cooler weather, many counties are now trending at or slightly below their 10 year average GDD.

Crop Updates

Asparagus – the cool wet weather has slowed down harvest and promoted purple spot on the spears.

Brassica Crops –The threshold for the first generation of cabbage maggot has been reached in Essex and will likely be active by next week in southern parts of the province. For cabbage 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. 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. An Emergency Use Registration for Cimegra (Group 30) has been approved for broccoli, Brussels sprouts, cabbage, and cauliflower against cabbage maggot for the 2025 field season. Damage from cutworms is widespread this year (Figure 1). Products registered for cutworm management are most effective when they are applied early when the cutworm larvae are small. Keep an eye out for flea beetles, diamondback moths, and imported cabbageworms this week.

Figure 1. Cutworm damage on a Brussels sprouts plant.

Celery – Transplants are establishing well, and most fields have been planted across Southwestern Ontario. The thresholds for aster leafhopper and tarnished plant bug have been reached in many areas across the province. Dig up wilted plants and inspect the roots/plug for cutworm larvae.

Cucurbits – hopefully the cooler temperatures are behind us and we can get busy planting. As the seedlings emerge, watch for striped cucumber beetles in the field. Even low populations can transmit the bacterial wilt pathogen. Thiamethoxam treated seed usually provides up to 6 weeks of beetle control.

Garlic – Scapes will likely be visible in the next two weeks on hardneck cultivars. Tipburn on older leaves is widespread across the province this year and may be due to the lack of moisture in March and April in some areas making it difficult to find plants that are still green to the tip. Register for this years Garlic Growers Association of Ontario Field Day on Saturday, June 7th. Go to https://www.garlicgrowersofontario.com/field-day-2025 to register.

Onion – Direct seeded fields are between the flag and 3 leaf stage. Transplants are doing well given they have had enough moisture to establish. Onion maggot flies are active in most regions; be on the lookout for wilted plants. Stake/count 50 or 100 plants now and count later in the seasons to determine how many onions make it to harvest. While scouting, keep on the lookout for cutworms and dig around suspect plants that look like they have been cut with scissors to look for cutworm larvae within the top inch of the soil surface (Figure 2). Control volunteer onions in neighbouring fields, as this can be a source for fungi inoculum like Stemphylium or pests like onion thrips that will be seen in the coming weeks.

Figure 2. Cutworm damage on an onion seedling.

Sweet corn – there is a lot of yellow corn around. This is due to the cool temperatures, delayed emergence and lack of root growth. Growth and colour will improve with warmer temperatures. Additional fertilizer is not necessary to address the poor colour.

Tomatoes – planting is about 65% complete for processing tomatoes and fresh market tomatoes are continuing with their staggered planting schedules. Be sure to keep scouting for early season insect pests like black cutworm, wireworm and Colorado potato beetle. The cooler weather will slow down the growth of transplants, making them vulnerable to these pests for longer than most years.

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***	342	288	153	93	35	192	288	70
Chatham-Kent*	507	439	260	174	79	312	439	137
Durham***	411	354	210	132	55	255	354	101
Essex*	547	478	295	199	90	351	478	158
Huron***	402	343	199	131	65	241	343	106
Kemptville***	404	350	206	132	63	250	350	106
Lambton**	464	398	231	150	69	282	398	118
Middlesex**	458	396	233	148	63	283	396	115
Norfolk**	448	385	218	135	56	268	385	102
Peterborough	373	317	175	106	40	217	317	80
Renfrew	384	332	194	125	63	237	332	100
Simcoe***	361	305	170	102	43	210	305	78
Sudbury***	239	204	116	79	42	141	204	66
Thunder Bay	64	55	29	13	2	37	55	8
Timiskaming***	222	187	108	72	35	130	187	58
Wellington Centre**	383	325	181	108	41	225	325	82
Wellington North**	388	332	185	121	54	229	332	96