VCR – Vegetable Crop Report – July 16th, 2026

Crop Updates

Brassica Crops – Broccoli and cauliflower head development has been uneven with the extreme heat this season. Tip burn and riciness is being observed in some fields. Rot in the main meristem and no head development could be the result of Swede midge damage that occurred several weeks earlier (Figure 1).

**Figure 1** – Swede midge damage can result in bacterial rot several weeks after the swede midge larvae have left. Photo: H. Fraser.

Carrots – Lots of heat related issues are being seen, including losses to heat canker in recently planted fields (Figure 2). Continue to irrigate where possible to reduce stress.

Garlic – Harvest is in full swing across the province. 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. Remove excess moisture from the crop as soon as possible as a slow cure will make it easy for pathogens to colonize wounds / bruises from harvest which will lower quality and the length of time the crop can be kept in storage. Be vigilant about reducing mechanical injury during harvest. If you find brown insect pupae while harvesting that looks similar to Allium leafminer pictured below, (Figures 3-4), please E-mail travis.cranmer@ontario.ca.

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

**Figure 4** – The relative size of Allium leafminer pupae found on the stem of harvested garlic July 7th, 2026 – B. McAuley.

Onions – Most fields are showing some Stemphylium lesions by now (Figure 5). If Penflufen was part of the seed treatment, do not start a foliar fungicide program with a group 7 fungicide. For the first application to manage Stemphylium, 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. Avoid applying products from the same chemical group one after the other to manage Stemphylium. For the second foliar product, Allegro 500F (group 29) or products containing a group 7 show the best efficacy, such as Sercadis, Aprovia, or Miravis Duo (group 7/3). 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). Avoid applying products from the same chemical group one after the other to reduce the selection pressure against group 7 or group 29 fungicides so that they can be used to manage Stemphylium for future years. Fusarium basal rot is common in fields that have been irrigated and are under black plastic. The levels of thrips are climbing with the heat. Apply no more than two consecutive insecticides from the same IRAC crop as thrips have a relatively short life cycle with multiple generations through the summer months and are at a high risk of developing insecticide resistance. The next generation of onion maggot is active in many areas across the province. Be on the lookout for stunted/wilted plants due to onion maggot over the next week.

**Figure 4** – Onion Stemphylium moving in on leaf tips.

Potatoes – Colorado potato beetles are still active and larvae are getting larger. Here is a list of registered products to use foliar against Colorado Potato Beetle. Some products should be targeted at younger larval stages so check the notes for instructions. If you applied a neonic seed treatment or in-furrow, do not follow up with a neonic (Group 4A) foliar. Consider border sprays as most feeding is near the edges of fields.

Symptoms of secondary growth are already being seeing in susceptible varieties. This includes chaining and the sprouting of new stems from tubers (Figures 5-6). Irrigate when possible to reduce stress during this time. There has been lots of air pollution and heat stress damage seen over the last week. Expect increased amounts of damage with the heat and poor air quality.

**Figure 5** – Secondary growth from potato tubers caused by stress.

**Figure 6** – Chaining and secondary tuber growths on potatoes.

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	1000000+
Bruce***	1004	906	637	482	299	721	906	415
Essex*	1496	1381	1054	852	583	1160	1381	757
Chatham-Kent*	1381	1267	948	757	516	1051	1267	673
Norfolk**	1270	1161	867	691	456	959	1161	608
Huron***	1158	1053	765	597	384	857	1053	521
Wellington**	1112	1013	744	582	374	828	1013	507
Simcoe County***	1136	1038	772	610	406	857	1038	537
Durham***	1200	1098	819	652	441	909	1098	578
Peterborough	1138	1038	766	604	391	854	1038	529
Kemptville***	1213	1113	828	663	449	919	1113	588
Sudbury***	939	857	639	510	336	709	857	449
Timiskaming***	931	848	637	509	334	702	848	449
Lambton**	1270	1160	857	686	453	953	1160	605
Thunder Bay	795	715	509	393	237	572	715	338
Middlesex*	1299	1192	893	717	483	989	1192	634
Renfrew	1046	958	711	571	394	790	958	510