The weather and pest forecasting dashboard is live! Check out values specific to your region at https://onvegetables.com/weather-dashboard/
Temperature – Temperatures remain in the mid to low 20s into the weekend before rising at the beginning of next week. Many regions may see temperatures in the 30s with the humidex. Temperatures are expected to drop again towards the end of next week. Sudbury temperatures are expected to remain stable. Cabbage maggot is at threshold in Huron, Wellington, Simcoe, Peterborough and Kemptville. Degree day data for each region is shown below.
Rainfall – There is a chance of showers at the beginning of next week for most of the province and throughout the week in northern regions. Some areas have already received small amounts of rain for September. All region came near and most surpassed their 10 year precipitation averages for August. Simcoe county received more than double it’s 10 year average. Precipitation data for each region is shown below.
Brassica Crops – Alternaria is becoming more widespread in some areas. Depending on the Brassica crop grown, not all fungicides are labelled for use; see Table 1 below for fungicides registered on different Brassica crop groups. Diamondback moths, imported cabbageworms, imported cabbage worms and tarnished plant bugs are active.
Carrot – Leaf blights remain the primary concern. Cercospora leaf blight can cause significant damage to the petioles and leaves (Figure 1).
Celery – Cercospora, Sclerotinia (pink rot, Figure 2), leaf curl and Fusarium yellows are active. Avoid scouting when leaves are wet as pathogens can spread easily on clothes/equipment throughout the field. Disc harvested blocks to reduce pest pressure and plant a cover crop to prevent soil erosion. Continue to scout for tarnished plant bugs, aster leaf hoppers, Leafminers and aphids.
Cucurbits – Conditions have been favourable for infection by Didymella bryoniae, the causative agent of Gummy Stem Blight. Look for hot spots of stems with oozing lesions, and for distinctive patterns on the skin of butternut squash (Figure 3). These lesions do not reduce the quality of butternut squash fruit, but do reduce marketability. This pathogen also causes black rot of pumpkin.
Aphids have been active in cucurbit fields, sprays for cucumber beetle can reduce populations of the beneficials that usually keep aphids in check. During wetter conditions aphid populations normally crash due to infection with natural fungi. Action is warranted if aphid populations are building on fruit.
Cucumber beetles remain active. Striped cucumber beetles have enjoyed continuous flushes through the season, and spotted cucumber beetle (Figure 4) populations are now increasing.
Squash vine borer Melittia cucurbitae (Figure 4) has been found in several areas. Management is preventative for this pest. Home and market gardeners sometimes excise the borers and allow vines to re-root but this can open the vines up to fungal infection. Look for sawdust-like frass around an entry hole on wilting plants, dissecting the stem will reveal the larvae.
Powdery mildew pressure remains high. Infection with powdery mildew can reduce fruit quality including poor internal colour development, and infection of the petiole (Figure 5) can reduce marketability.
Squash bugs are active and can cause crop damage (Figure 6) but are not usually a problem in commercial fields. Colonies with many different instars are typical. Squash bugs prefer to feed on leaves but will move to fruit once leaves are no longer available.
Onions – Most fields have started to lodge or have been harvested already. No downy mildew outbreaks have been confirmed. Scout patches of the field that are not as green and look closely at the leaves to ensure that there is no fuzzy growth. The 2020 Muck Crops Research Station Variety Trials Evaluation Days are September 8 – 11. Please call the Muck Station at 905-775-3783 or E-mail Shawn at firstname.lastname@example.org to book your timeslot. Timeslots are available from 8:30AM to noon or 1:00 to 4:00 with a maximum of 10 people per time slot. Access to the Muck Station will be restricted and health protocols will be enforced.
Peppers – Hand harvest continues for processing and fresh market peppers. Many growers have noticed a yield boost from the recent rain events. No pepper weevils have been captured on outdoor survey traps. Growers should continue to scout for signs of the pest and check traps regularly. If you have caught a weevil and would like to have it looked at, please email pictures to Amanda Tracey at email@example.com or call 519-350-7134.
Potatoes – Late blight has been confirmed in one New York County and probably in another NY county. Remain vigilant with scouting and fungicide application. Look out for Botrytis grey mould and white mould developing at the bottom of the canopies. Scout later harvested fields for black cutworm. As harvesting ramps up, keep an eye out for tuber diseases going into storage such as pink rot (Figure 7).
Tomatoes – Harvesting for processing and fresh market is ongoing. New York has just reported an occurrence of Late blight in potato and tomato, which occurred approximately 2 weeks ago. The first observation of symptoms in Ontario occurred on potato in Norfolk County over a week ago. No new instances of late blight have been reported in Ontario this week. Tomato growers, especially those with late varieties that still have a significant amount of green foliage, should continue to scout for symptoms and apply general fungicides with activity against Phytophthora infestans. If a field is high risk (i.e. symptoms in the field or neighbouring crop), growers should consider applying a late blight specific fungicide. Please see the post “Late Blight Update – August 26, 2020” for more information and links to additional resources. Always be sure to read product labels carefully before any pesticide application.
NOTE: Data as of September 2nd, 2020
Pest Degree Day Forecasting
|Pest||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: