VCR – Vegetable Crop Report – August 18th, 2022

Temperature – Most regions continue to match or surpass their 10 year GDD cumulative average except Peterborough which has not caught up after cooler weather in July. Daytime temperatures are expected to be in the mid- to high 20s throughout next week with nighttime temperatures ranging from the mid- to high-teens and up to the low 20s further south.

Precipitation – Most regions received little to no rain over the past week except for Durham and Peterborough. Showers with a chance of thunderstorms are forecasted over the weekend and into the beginning of the week throughout Ontario. Some counties may also see rain again toward the end of next week.

Crop Updates

Brassica Crops – Transplanting for late broccoli has finished. Alternaria is starting to show in some fields. Alternaria can cause head rot in broccoli and cauliflower if spores are able to infect the beads/curds and secondary bacteria can cause rot. Over the next few weeks, be on the lookout for brassica downy mildew.

Celery – The wet weather has been great to allow celery to bulk-up, but it has also been conducive for many foliar and soil pathogens. Blackheart and Fusarium yellows can have very similar symptoms of leaf dieback and a rotted crown. To determine if you are seeing Fusarium yellows, take a cross-section of the crown and look for discolouration within the heart (Figure 1). Bacterial leaf spot and celery leaf curl are active. Scout once the crop canopy is dry for Cercospora, Septoria and leaf curl. Tarnished plant bugs continue to be active.

Figure 1. Cross-section of plant with fusarium discolouriation within the crown – August 2020.

Garlic – When choosing a field for the 2022-2023 field season, avoid a field that has been planted in garlic, leeks or onions in the last 3 years. If you are obtaining new planting stock for 2022-2023, read this first: https://onvegetables.com/2022/08/05/garlicplanting/. If purchasing new planting stock, be sure to test it for bulb and stem nematode before planting it. Cloves can look healthy and show no symptoms of infection even though low levels (i.e. 10 nematodes/gram) are present. It is often not until the third or forth year of planting that low levels of nematodes become high populations that cause severe basal rot and unmarketable bulbs.

Onion – Early transplants continue to be harvested and direct seeded onions are starting to lodge. Stemphylium leaf blight and tipburn is starting to take hold in direct seeded fields. Royal MH can be applied for sprout control when 50% of the crop has lodged and there are green tops that are still present to absorb the product. Apply at least 10 days before the crop is harvested. Now is a great time to assess damage plots that were put up in the spring. Determining the number of plants that survived out of the 100 germinated/transplanted plants that were counted at the start of the season is valuable information to determine what percentage of plants died due to onion maggot, drought, or some pest or pathogens.

Pest Degree Day Forecasting

*NOTE: Data as of August 17th, 2022

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
Essex*	2087	1941	1527	1280	944	1661	1941	1163
Chatham-Kent*	1899	1758	1360	1122	759	1489	1758	1011
Norfolk**	1868	1730	1334	1091	725	1463	1730	978
Huron***	1673	1538	1154	921	574	1277	1538	812
Wellington**	1638	1505	1124	892	549	1247	1505	788
Simcoe County***	1667	1534	1156	923	582	1278	1534	817
Durham***	1777	1638	1248	1012	652	1374	1638	899
Peterborough	1583	1450	1069	843	507	1191	1450	736
Kemptville***	1778	1637	1249	1017	658	1372	1637	906
Sudbury***	1482	1364	1019	804	475	1133	1364	703