VCR – Vegetable Crop Report – July 30th, 2026

Crop Updates

Brassica – Conditions have been favourable for Xanthomonas or black rot of Brassicas. Populations of thrips are increasing and could become problematic in cabbage. Diamondback moths, imported cabbageworms, tarnished plant bugs and aphids remain elevated in many areas. The threat of downy mildew and bacterial pathogens remains high given the high humidity and colder nights (Figures 1-2).

**Figure 1** – White fuzzy growth on downy mildew lesions on broccoli – T. Cranmer.

**Figure 2** – Lower leaves infected with downy mildew turning yellow – T. Cranmer.

Cucumbers – Overall disease pressure has been lower than average. As of July 30, there have been no reports of downy mildew in the Great Lakes region. Anthracnose, fusarium and verticillium wilt have been found at low levels in some fields.

Mites appeared in high numbers in both Kent and East Elgin last week. Mite pressure can build very quickly with few noticeable signs. Aborted fruit and “off colour” leaves are often one of the first signs of a mite infestation.

Garlic – Harvest is wrapping up. Garlic is fully cured when the outer skins are dry and crispy, the center of the cut stem is hard, and the neck is constricted at the bulb. Depending on the moisture in the crop at harvest, the dry weight is typically 18-22% less than the fresh weight at harvest. When curing, maintain good airflow to prevent pockets of no air movement. If you are using heat to improve the water holding capacity of the air, be careful to avoid temperatures above 43°C which may lead to waxy breakdown. Waxy breakdown is a disorder when the cloves turn yellow or translucent and become jelly-like in texture from high temperatures in the field, during harvest or while curing. While trimming or handling bulbs, rogue out bulbs with fusarium / bulbs with a missing or rotten basal plate and do not keep them for seed. As mentioned in last weeks VCR, be on the lookout for Allium leafminer pupae in stems, pictured below, (Figure 3). If you find pupae and are looking to get the exact insect identified, please E-mail travis.cranmer@ontario.ca.

**Figure 3** – The relative size of Allium leafminer pupae found on the stem of harvested garlic July 7th, 2026 – B. McAuley.

Onion – The rain has been welcoming in many areas as direct seeded onions are starting to bulk. Stemphylium is progressing in most fields (Figure 4). Bacterial rots are starting to be seen in some fields that were irrigated through the dry periods in July and bulbs with split basal plates are also common (Figure 5). As transplants start to lodge, give more attention to counting thrips at the edges of direct seeded fields that are adjacent to fields of transplants. Keep an eye out for onion downy mildew given the cooler temperatures in some areas over the past week. Downy mildew of onions prefers temperatures below 22°C and extended periods of leaf wetness. A full list of products registered for onion downy mildew can be found on the Ontario Crop Protection Hub.

**Figure 4** – Onion infected with stemphylium creating tan lesions with brown to black streaking that elongate through the leaf – T. Cranmer.

**Figure 5** – Onion with a split basal plate – T. Cranmer.

Pumpkins and Squash – Powdery mildew is starting to move into the area. The best control is achieved with well-timed fungicide sprays in late-July through August. Use a 7-14 day interval based on disease pressure and weather conditions. Powdery mildew does not need a lot of moisture to develop; however it does slow considerably at temperatures above 30°C.

Snap Beans – White mould pressure typically increases as we head into August. Risk factors include thick crop canopies, heavy dew, intermittent rains and cooler nighttime temperatures. Apply fungicide controls at first bloom with a second application 7 days later if the conditions persist.

Sweet Corn – Weather patterns suggest a low-to-moderate risk of corn earworm pressure. Populations usually increase significantly over the month of August as the moths are carried north by the prevailing winds.

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***	1218	1106	795	612	387	893	1106	531
Essex*	1755	1626	1257	1027	716	1377	1626	918
Chatham-Kent*	1620	1492	1131	913	629	1249	1492	814
Norfolk**	1497	1374	1039	834	557	1144	1374	737
Huron***	1372	1253	923	728	473	1029	1253	638
Wellington**	1324	1211	900	710	460	998	1211	621
Simcoe County***	1363	1250	942	753	507	1042	1250	666
Durham***	1434	1318	997	802	549	1101	1318	714
Peterborough	1357	1243	929	739	483	1030	1243	650
Kemptville***	1432	1319	995	804	552	1100	1319	717
Sudbury***	1148	1052	792	635	419	876	1052	560
Timiskaming***	1130	1034	780	625	408	860	1034	550
Lambton**	1516	1391	1047	848	573	1157	1391	753
Thunder Bay	1026	932	683	540	341	760	932	471
Middlesex*	1541	1419	1079	875	598	1188	1419	778
Renfrew	1241	1142	862	700	490	952	1142	628