VCR – Vegetable Crop Report – July 23rd, 2026

Crop Updates

Brassica Crops – Up until this past week, conditions have accelerated nutrient disorders in some head brassicas fields, from tip dieback on leaves to uneven head development to leaf edema. For Alternaria fungicide management, see the Crop Protection Hub for a list of registered products and max number of applications for the specific brassica crop you are growing. Bacteria rot in cabbage and Xanthomonas black rot have also been identified. The second wave of cabbage maggot flies has been active in many counties across the province. Dig up wilted plants and inspect roots for cabbage maggot larvae. There have been lots of double/triple heads in cabbage and multiple growing points in other Brassicas which was likely due to Swede midge damage earlier in the season. Diamondback moth pressure continues to be high, there is still a bit of flea beetle damage, and some field perimeters are being targeted by slugs (Figure 1). Watch for brassica downy mildew, especially near windbreaks and areas that receive any sort of shade throughout the day, given the cooler weather with longer periods of leaf wetness we will see this week and into next.

**Figure 1** – Slug feeding on the leaf of a Brussels spouts plant – July 21^st, 2026.

Garlic – Harvest continues. Witches brooming observed earlier in the season has resulted in a bunch of misshapen bulbs with multiple scapes (Figure 2). Remove bulbs from direct sunlight as soon as possible and be mindful of how long garlic is sitting in wagons/crates when there is no forced air present. Waxy breakdown occurs when the bulb experiences high temperatures in the field, during curing or in storage. Be vigilant about reducing mechanical injury during harvest. Remove excess moisture from the crop as soon as possibles as a slow cure will make it easier for pathogens, like Fusarium or Penicillium blue mould to colonize wounds / bruises from harvest. When curing, controlling humidity is the most important variable to control. Curing over a long period of time (eg. 14+ days), can allow bulb mites to acclimatize and cause problems in storage. Be on the lookout for Allium leafminer pupae in stems, pictured below, (Figures 3). If you find pupae and are looking to get the exact insect identified, please E-mail travis.cranmer@ontario.ca.

**Figure 2** – Bulbs that had witches brooming earlier in the season – July 22^nd, 2026.

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

Onions – Many fields are still green to the tip, but most fields are showing some Stemphylium lesions by now. Allegro 500F (group 29) is registered for suppression of Stemphylium, Botrytis leaf blight and purple blotch on dry bulb onions. A product containing mancozeb (group M3s, such as Manzate Pro-Stick, Dithane Rainshield, and Penncozeb 75 DF Raincoat) may provide protection against Stemphylium if it is being applied to manage onion smut, Botrytis or Alternaria/Purple Blotch. Allego 500F and products containing a group 7 show the best efficacy, such as Sercadis, Aprovia, or Miravis Duo (group 7/3). Avoid applying products from the same chemical group one after the other to manage Stemphylium. Research has shown that there is very high resistance in Stemphylium to one of the fungicides in Quadris Top (group 11/3) and in Luna Tranquility (group 7/9). The levels of thrips are starting to climb in some fields that have received two applications of Movento 240 SC (group 23). Apply no more than two consecutive insecticides from the same IRAC crop as onion thrips have a relatively short life cycle with multiple generations through the summer months and are at a high risk of developing insecticide resistance. Fusarium basal rot is common in fields that have been irrigated and are under black plastic. Over the next week, be on the lookout for onion downy mildew (Figure 4) and stunted/wilted plants due to onion maggot. A full list of products registered for onion downy mildew can be found on the Ontario Crop Protection Hub.

**Figure 4** – 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***	1104	1000	710	541	337	801	1000	467
Essex*	1629	1507	1159	943	653	1272	1507	841
Chatham-Kent*	1503	1382	1042	838	575	1153	1382	746
Norfolk**	1381	1265	951	761	504	1050	1265	670
Huron***	1261	1149	841	659	425	939	1149	576
Wellington**	1216	1110	820	644	415	911	1110	562
Simcoe County***	1251	1145	858	683	458	950	1145	602
Durham***	1314	1205	906	724	492	1002	1205	643
Peterborough	1242	1134	841	666	431	936	1134	583
Kemptville***	1309	1203	901	723	492	998	1203	643
Sudbury***	1035	946	707	564	369	784	946	496
Timiskaming***	1018	928	696	554	358	769	928	487
Lambton**	1394	1276	953	768	514	1056	1276	680
Thunder Bay	904	817	590	460	283	660	817	398
Middlesex*	1419	1304	985	795	539	1087	1304	705
Renfrew	1129	1036	774	624	433	859	1036	559