Temperature – All counties continue to meet or rise slightly above their 10 year average GDD trends. Daytime temperatures have dropped to the mid- teens to low 20s after yesterday’s stormy weather and they are forecasted to remain consistent throughout next week. Some counties may see single digit nighttime temperatures at the start of the weekend.
Precipitation – All counties received at least some rain over the past week. However Norfolk county received approximately 40% of it’s 10 year average rainfall total for June yesterday with a whopping 36.4mm and Simcoe received approximately 25%. Most counties fell slightly behind their 10 year average rainfall for May except for Wellington, which was slightly above, and Kemptville which received almost double their 10 year average total monthly rainfall. Rain and possible thunderstorms in most counties are forecasted for after the weekend and again towards the end of the week. A few counties may also see rain with a risk of thunderstorms tonight continuing into tomorrow.
Brassica Crops – Transplants are establishing well if there is adequate moisture with some plants showing wilting on days over 30C. The threshold for the first-generation emergence of cabbage maggot has been reached in most regions other than Sudbury. Flea beetles, swede midge, slugs and cutworms (Figure 1B) remain active. Diamondback moths and imported cabbageworms are likely to be observed very soon. Pull up wilted plants and inspect roots for insect larvae. Wilted plants may be due to heat, millipedes (Figure 1A) or seedcorn maggot damage and if the leaves are turning purple, the wilt may be due to wirestem, caused by Rhizoctonia (Figure 1C).
Celery – Transplants are establishing well, and most fields have been planted across Southwestern Ontario. The thresholds for aster leafhopper and tarnished plant bug has been reached across the province. Dig up wilted plants and inspect the roots/plug for cutworm larvae.
Cucurbits – Striped cucumber beetles (Figure 2) are migrating to pumpkin, squash, cucumber, and melon fields. If an insecticidal seed treatment, such as thiamthoxam, was not used, be prepared to make a foliar application. The threshold is one beetle per plant. The beetles cluster feed, so large numbers will commonly be found on random plants, or in specific areas of a field. Beetle feeding at this stage has a high risk of transmitting the bacterial wilt pathogen. Where an insecticidal seed treatment has been used, it is common to find large numbers of dead beetles at the base of the plant along with some feeding damage. Beetles ingest the insecticide while they feed. It is also common for the beetles to enter the field in flushes. Frequent scouting is important to properly determine if a foliar insecticide application is warranted.
Garlic – Plants are starting to send out the scape leaf and the scapes on ‘Music’ are starting to emerge. Scapes will likely emerge in most regions in SW Ontario over the next 5-10 days. Tipburn is widespread across the province this year and may be due to frost damage, lack of moisture over the past month or herbicide injury. It is difficult to find plants that are still green to the tip. Irrigation may be required for bulbs to size well in areas that have had little precipitation over the past month. Continue to scout for damaged leaves as this will likely be due to leek moth damage. Leek moth leaves what looks similar to sawdust on the top of the leaves (Figure 3). Depending on the area, the second flight of leek moth will be active over the next two to three weeks. Use sticky cards with lures to monitor populations, and target the second generation of larvae a week after the peak flight. Register for the next Garlic Production and Pest Management workshop near Janetville, ON, that takes place Friday, August 19th from 9:30-4:30. Register by calling 1-877-424-1300 or filling out this online form: https://survey.clicktools.com/app/survey/go.jsp?iv=1y59n0qcz8rld.
Leafy Greens – Cutworms are active and leafy greens that are grown from seed are at a greater risk. If leaves look like they were cut at the soil line in the field, dig up around the plant to look for cutworm larvae (Figure 4). The larvae comes out at night to feed, so if management strategies targeting this pest are implemented, it should be when the larvae are active and the product can make contact.
Onions – Earliest direct seeded onions are at the third leaf stage while the majority of fields are in the flag or 2nd leaf stage. Transplant are doing well given they have had enough moisture to establish. Onion maggot flies are active in all regions; be on the lookout for wilted plants. Control volunteer onions in neighbouring fields as this can be a source for fungi inoculum like Stemphylium or pests like onion thrips. Also be on the lookout for black cutworms over the next two weeks. Cutworms can cause damage that looks like the onion has been cut with scissors above the soil line (Figure 4). Dig around suspect plants to look for cutworm larvae within the top inch of the soil surface.
Pest Degree Day Forecasting
*NOTE: Data as of June 1, 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: