VCR – Vegetable Crop Report – May 22nd, 2025

Welcome back to the next VCR of 2025!

Although many areas experienced lower temperatures this week, excluding the northern counties of Sudbury, Thunder Bay, and Timiskaming, all counties continue to trend above their 10 year average GDD.

This past week was also a very wet one for many counties. Chatham-Kent and Middlesex are both close to their 10-year average precipitation for the month. The counties of Essex and Lambton have surpassed their 10-year averages for May.

Crop Updates

Asparagus – the recent stretch of cold, wet, windy weather may result in an increase of purple spot (Stemphylium), especially as the weather begins to warm up and the fungus takes advantage of minute wounds caused by wind or sand blasting.

Brassica Crops – Plants are establishing well, and transplanting continues across the province. The degree day threshold for cabbage maggot emergence has been met in Essex, CK, Lambton and Middlesex counties which means eggs should be hatching out soon. 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. 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. The nighttime lows have generally been above temperatures that would result in frost damage in head brassicas in most regions. In areas with hard frosts, plants may see older, outer-most leaves turn yellow and wilt over the next week. Plants that were not properly hardened off before transplant are at a greater risk of frost damage. Continue to dig up wilted plants and inspect the roots for wireworms, cabbage maggot larvae, or millipede damage.

Cucurbits – planting will begin to ramp up over the next week. Cucurbit crops are sensitive to chilling injury. Optimum growth requires temperatures above 20 C. Planting can occur when the soil temperatures are consistently over 16 C. Avoid planting when the air temperature is forecasted to drop below 10 C. Take soil temperature readings in the morning for an accurate idea of the minimum soil temperature.

Garlic – Cool nights and drier conditions have led to many fields showing yellow tips on older leaves, despite whether herbicides have been applied in the past. Leek moths have been captured in most areas across the province. Leek moths can be monitored to inform insecticide timing by using Delta 1 traps and more information can be found here: March 7, 2025 ONVeg article. The Garlic Growers Association of Ontario is hosting the 2025 field day Saturday, June 7th at Felix Fumanek Farms near Arthur, Ontario. Equipment from multiple manufacturers will be on display, along with products from fertilizer and pest control product suppliers. The agenda includes presentations on results from past trials, a tour of a new garlic curing and storage facility along with a field tour of cultivar / clean seed demonstration trials Registration starts at 9:00, the agenda starts at 9:30 and goes until 4:30. Lunch will be provided. Felix Furmanek Farms is located at 8818 Wellington County Rd 14, Arthur, Ontario, and all are welcome to join, rain or shine. Please register for the field day by going to https://www.garlicgrowersofontario.com/field-day-2025.

Onion – The majority of direct seeded onions fields have emerged and are in the loop or flag stage. Onion maggot and seedcorn maggot flies have reached their threshold for the first-generation emergence in most counties and damage from early season activity will likely be observed shortly. Dig up wilted plants and inspect roots for onion maggot larvae. Once seeded onions have emerged, stake out 100 plants as a damage plot. These damage plots will be valuable to monitor the amount of damage due to maggot flies or other pests throughout the season. If you were unable to attend the Onion IPM scouting workshop, a recorded version can be found at: https://www.youtube.com/watch?v=moY8MPmzy88

Potatoes – With these recent rains and cooler soil temperatures, watch for seed and emergence issues caused by Rhizoctonia and seed borne late blight. If you are seeing seed rot or blackleg symptoms early in the season, you can submit samples for free to the Ontario Potato Soft Rot and Blackleg survey. More details and contact information can be found here: Potato Bacterial Soft Rot Survey – ONvegetables. Remember to sign up for the Ontario Potato Scout Training next week Wednesday May 28^th: 2025 Ontario Potato Scout Training – ONvegetables

Tomatoes – planting has begun for processing tomatoes and fresh market tomatoes are starting with their staggered planting schedules. Be sure to keep an eye out for early season insect pests like black cutworm (Fig. 1), wireworm (Fig. 2) and Colorado potato beetle (Fig. 3) . These pests are becoming more of an issue with the loss of some key insecticides and early detection is key to managing them effectively. Make sure to read all product labels carefully before any pesticide application.

Fig. 1. Damage to tomato transplant caused by black cutworm.

Fig. 2. Wireworm damage and larva inside tomato transplant stem

Fig. 3. Colorado potato beetle egg mass on underside of tomato leaf.

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***	283	237	126	79	31	157	237	60
Chatham-Kent*	438	378	223	153	73	267	378	123
Durham***	341	292	173	110	47	209	292	86
Essex*	488	426	265	182	90	314	426	148
Huron***	359	307	184	124	62	219	307	101
Kemptville***	342	294	172	112	55	209	294	90
Lambton**	418	358	213	145	71	256	358	118
Middlesex**	407	352	210	139	63	253	352	110
Norfolk**	406	350	203	133	60	247	350	105
Peterborough	319	270	149	93	40	184	270	73
Renfrew	317	273	158	103	53	193	273	83
Simcoe***	312	263	149	95	43	183	263	74
Sudbury***	181	153	86	60	32	104	153	50
Thunder Bay	0	0	0	0	0	0	0	0
Timiskaming***	160	132	74	52	26	88	132	42
Wellington Centre**	333	282	159	97	39	196	282	74
Wellington North**	338	289	163	107	49	200	289	85