VCR – Vegetable Crop Report – July 27th, 2023

Welcome back to the VCR!

Brassica Crops – Conditions have been favourable for Alternaria and Brassica downy mildew. Many fields that had waterlogged roots are starting to wilt during the heat of the day. Not only is wilt caused by extreme temperatures, wilt can also be caused by cabbage maggots, wireworms, clubroot and other pests/pathogens that are targeting the roots. It is a good idea to dig up wilted plants with a shovel and examine roots to see if any pests are present or if the wilt is caused from the heat.

Garlic – Harvest continues across the province. As garlic cures, check bulbs in the middle of pallet boxes or totes regularly to get a good sense of how the entire crop is drying out. Thinking of planting a new cultivar or purchasing new planting stock for 2024? Test any new planting stock for bulb and stem nematode before planting in your field. Low levels of 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/

Onions – Some areas may be at a high risk for onion downy mildew given the high humidity, heavy dews and colder mornings. While there are many products registered for onion downy mildew, past work by the Ontario Crops Research Centre – Bradford has shown that Orondis Ultra (groups 40/49), Zampro (groups 45/40) and Ridomil Gold Mz (groups 4/M3) are effective. Stemphylium is progressing in many fields, especially those where the older leaves are senescing early due to excess moisture. The second wave of onion maggots are active and causing damage in some onion growing regions while the pressure of thrips has not increased substantially in areas that have had a lot of precipitation over the past week.

Peppers – Phythophthora and fusarium are starting to take down some plants in fields across Southwestern Ontario. Continued wet weather will only help these diseases to spread and become more severe. Growers need to identify any plants that are wilting during the heat of the day and get them diagnosed to know what is affecting them. Identifying the issue early on can help you to protect the remaining healthy plants through the use of registered fungicides. For root and crown rot, a soil application is usually best. Make sure to read all labels carefully before any pesticide applications. For questions or more information, please reach out to Amanda Tracey at 519-350-7134 or at amanda.tracey@ontario.ca.

Tomatoes – Late blight spores have been detected on spore traps in Essex and Elgin counties. This combined with reports of late blight symptoms in potato near Alliston and Shelburne means that grower should be using preventative fungicides with late blight activity in their tomato crops. Growers should also be scouting fields for any symptoms of late blight (Figure 1) and getting it confirmed by an OMAFRA Specialist. This is a community disease and it takes all of us working together to keep our crops healthy. If you have any questions or need help with a diagnosis, please contact Amanda Tracey at 519-350-7134 or at amanda.tracey@ontario.ca.

**Figure 1 –** Wet looking, green-grey foliar lesions of late blight on tomato plant.

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***	1188	1084	790	611	386	885	1084	533
Essex*	1534	1408	1067	868	593	1173	1408	774
Chatham-Kent*	1438	1316	986	791	527	1091	1316	701
Norfolk**	1412	1291	969	776	514	1070	1291	685
Huron***	1279	1166	863	678	434	959	1166	591
Wellington**	1256	1148	852	670	428	948	1148	586
Simcoe County***	1279	1170	865	686	445	962	1170	602
Durham***	1376	1261	944	759	507	1043	1261	672
Peterborough	1290	1179	866	680	434	965	1179	595
Kemptville***	1415	1304	991	799	540	1093	1304	706
Sudbury***	1199	1100	820	648	422	911	1100	568
Timiskaming***	1167	1068	783	611	391	876	1068	532
Lambton**	1387	1269	943	753	496	1046	1269	663
Thunder Bay	1002	908	646	494	288	731	908	422
Middlesex*	1398	1282	966	775	514	1066	1282	687
Renfrew	1408	1299	990	799	545	1091	1299	711