VCR – Vegetable Crop Report – May 21st, 2026

vegetablecropreport

21 hours ago

Most regions with the exceptions of Sudbury, Thunder bay and Timiskaming are above their 10-year averages for GDD. Many areas have seen strong winds over the past week leading to dust clouds in areas with drier fields.

Strong winds over the past week, coupled with recent field preparation and planting activities, has led to dust clouds in many areas with drier fields – J. Mosiondz May 18th, 2026.

Crop Updates

Cutworms – Insect forecasts and trapping programs are indicating that there has been increased potential for black cutworm moths moving into the Great Lakes region. Moths are attracted to green cover for egg laying. This includes winter annual plants like chickweed or overwintering cover crops. In the coming weeks when scouting vegetable crops, look for signs of above ground feeding and cut stems of seedlings. The larvae are often found in the top 2.5 cm of the soil at the base of the plant.

Asparagus – As the temperatures continue to improve, scout for asparagus beetle adults and egg masses in both the production fields and younger fields that have recently been released. Damage from larval feeding is most impactful in these immature plantings.

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. Scout for cutworm and flea beetle damage over the next week. Products registered for cutworm management are most effective when they are applied early when the cutworm larvae are small. Damage on the lower leaves of plants with no signs of lepidopteran pests may be the result of early-morning slug feeding.

Cucurbits – As we move into the final week of May and planting begins to ramp up, consider soil and air temperatures before making the decision to plant. For transplants, chilling injury occurs at temperatures below 10°C. While the plants will recover from cool temperatures, the damage can have a lasting impact on the health and vigour of the crop and the early development of flowering tissue. The minimum soil temperature for direct seeded cucurbits is 15°C. Below this level the seeds will be slow to germinate and more prone to early season stand losses.

Garlic – Tipburn is widespread across the province, but newer leaves are generally looking better. 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. Most plants are past the 5th leaf stage, so avoid applying nitrogen to reduce the number of rough bulbs at harvest as well as to encourage longer storage life. Register for the Garlic Growers Association 2026 field day Saturday, June 6th at Great Lakes Family Farms near Grand Bend, 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 garlic trials, industry, and minor use updates as well as a tour of a new garlic curing and storage facility. Registration starts at 9:00, the agenda starts at 9:30 and goes until 4:30. Lunch will be provided. Great Lakes Family Farms is located at 70748 B Line, Grand Bend, Ontario, and all are welcome to join, rain or shine. Please register for the field day by going to https://www.eventbrite.ca/e/field-day-2026-tickets.

Onions – Direct seeded fields are between the flag and 3 leaf stage. The extreme temperatures have been rough on some fields. 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 1). 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 1** – Cutworm damage on an onion seedling.

Potatoes – Planting is wrapping up on the North shore of Lake Erie. Conditions have been quite dry as of late. Planting continues in Alliston and Shelburne. The season started cool and wet but conditions have improved.

Sweet corn – Scout young plantings to assess the plant stand and early season growth. If there are gaps in the plant stand, or signs of variable growth, look for wireworm or seed corn magot activity in the root zone. Additionally, take a look at the overall health of the root system to rule out root rots or seedling decay. These problems are usually more prevalent in cool, wet springs when emergence and early growth are delayed.

Tomatoes – Due to cooler nighttime temps and recent rain events, there is a slower start to tomato planting this spring. Planting has started and is ongoing 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 (Figure 2), wireworm (Figure 3) and Colorado potato beetle (Figure 4) . These insect pests can cause significant damage to transplants, and early detection is key to managing them effectively. Make sure to read all product labels carefully before any pesticide application.

**Figure 2** – Cutworm damage on a young tomato plant.

**Figure 4** – A cluster of Colorado potato beetle eggs laid on the underside of a 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***	238	197	95	48	19	124	197	34
Essex*	521	461	299	207	102	350	461	167
Chatham-Kent*	441	383	232	154	78	280	383	125
Norfolk**	387	334	208	144	73	244	334	116
Huron***	312	262	143	86	34	179	262	65
Wellington**	288	244	141	89	39	170	244	68
Simcoe County***	273	230	132	82	38	161	230	62
Durham***	298	252	142	86	36	175	252	67
Peterborough	286	242	138	88	36	170	242	68
Kemptville***	310	266	149	95	44	184	266	75
Sudbury***	136	108	51	28	10	68	108	20
Timiskaming***	109	82	38	20	7	49	82	14
Lambton**	388	332	195	133	58	236	332	106
Thunder Bay	86	62	21	11	5	30	62	8
Middlesex*	396	343	207	139	64	248	343	110
Renfrew	254	214	112	68	30	143	214	54