VCR – Vegetable Crop Report – August 6th, 2026

Crop Updates

Brassica Crops – Alternaria leaf spot is starting to progress in some fields (Figure 1). Alternaria can cause head rot in broccoli and cauliflower if spores are able to infect the beads/curds and secondary bacteria can cause rot. See the Ontario Crop Protection Hub for a list of fungicides registered to manage Alternaria on broccoli, Brussels sprouts, cabbage, cauliflower and kale. Conditions have also been favourable for Brassica downy mildew and Sclerotinia while mould in some regions. After blocks are harvested, be sure to incorporate all crop residue to help lower amount of surviving of larvae and inoculum available to infest and infect later plantings.

**Figure 1** – Alternaria causing an uneven dome on a head of broccoli.

Garlic – Most garlic has been cured and is going into storage. Once cured, table stock can be kept at a temperature of 0.5°C at a relative humidity of 55-65% and planting stock can be kept above 14°C (up to 18°C) at a relative humidity of 55-65%. Avoid a relative humidity above 70% or temperatures between 3-14°C as this can promote sprouting in storage. Stained bulb wrappers on bulbs headed to storage may be due to a bacterial pathogen, such as Pseudomonas (Figure 2). To reduce the chances of Pseudomonas next year, avoid saving bulbs with missing or stained bulb wrappers for planting stock and avoid planting in poorly drained fields. Consider planting in raised beds if there are concerns of flooding in any part of the growing season. If you are purchasing planting stock for this fall, remember that low levels of stem and bulb nematodes can be found in planting stock that otherwise looks great. Here’s an article summarizing the things to consider before purchasing new garlic planting stock: https://onvegetables.com/2022/08/05/garlicplanting/.

**Figure 2 –** Bulb with staining on the bulb wrapper caused by the pathogen *Pseudomonas cedrina.*

Onions – Transplants are being harvested and some direct seeded fields are starting to lodge. The weather has been conducive for downy mildew (Figure 3) development in many onion growing areas. Past research at the Ontario Crops Research Centre – Bradford has shown that Orondis Ultra (groups 40/49), Zampro (groups 45/40) and Orondis Gold (groups 4/49) are effective for controlling this disease and are most effective when they are applied as a protective application before infection can occur. Stemphylium leaf blight is slowly causing tip dieback, but it is not as severe relative to previous years for this time in August. As fields of transplants are harvested, be mindful of younger, direct-seeded onions in border fields as the level of thrips may surge as they move to a greener crop, especially in this hot and dry weather.

**Figure 3** – Onion downy mildew found in a community garden in Guelph – July 19^th, 2026.

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***	1338	1220	888	691	445	993	1220	602
Essex*	1884	1748	1359	1115	782	1486	1748	999
Chatham-Kent*	1741	1607	1225	992	688	1349	1607	887
Norfolk**	1615	1485	1129	911	612	1242	1485	806
Huron***	1488	1362	1012	802	526	1124	1362	705
Wellington**	1436	1316	984	780	509	1089	1316	684
Simcoe County***	1480	1360	1031	828	561	1137	1360	734
Durham***	1560	1437	1096	887	612	1206	1437	791
Peterborough	1477	1355	1021	817	540	1129	1355	721
Kemptville***	1561	1441	1097	891	618	1208	1441	797
Sudbury***	1267	1164	884	713	475	974	1164	631
Timiskaming***	1241	1138	863	694	456	950	1138	612
Lambton**	1644	1512	1147	933	637	1264	1512	831
Thunder Bay	1138	1038	768	610	391	852	1038	535
Middlesex*	1661	1533	1171	954	656	1288	1533	850
Renfrew	1352	1247	949	776	548	1046	1247	698