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.
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.
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|
*- Bivoltine region for ECB. First Peak Catch: 300-350 DD, Second Peak Catch 1050-1100 DD
**- Overlap region for ECB. First Peak Catch: 300-350 DD Second Peak Catch 650-700 DD, Third Peak Catch 1050-1100 DD
***-Univoltine region for ECB. Peak Catch 650-700 DD
Use these thresholds as a guide, always confirm insect activity with actual field scouting and trap counts.
Select a region below for the latest weather, crop and pest degree day information: