Temperature – Growing Degree Days still lag marginally behind in many regions but are ontrack to catch up with the 10 year average value. Temperatures may cool slightly over the weekend but high temperatures will return into the next week across Ontario. Onion maggot, Asterleaf hopper, and Tarnished Plant Bug thresholds have been triggered in all regions. Carrot Rust fly thresholds have been triggered in Huron, Wellington, Simcoe counties, Peterborough, and Kemptville. Cabbage Maggot has been triggered in Essex county. Seedcorn maggot is at threshold in most counties excluding Essex, Chatham-Kent, and Norfolk which have all passed the first peak. Degree day data for each region is shown below.
Rainfall – All regions fell behind 10-year average values except for Simcoe county which surpassed its 10-year average rainfall for May. Some rain showers or thunderstorms may occur over the weekend and toward the end of next week. Sudbury may see scattered showers throughout the week. Precipitation data for each region is shown below.
Asparagus – Warm temperatures led to rapid spear emergence which produced a large quantity of asparagus in a short time. Last week’s fluctuating temperatures have encouraged Stemphylium purple spot in many areas, some fields have high incidence. Begin scouting immediately after harvest is complete to determine when a spray program will need to be initiated. Fusarium and Phytophthora symptoms have been observed in some areas: early symptoms were difficult to differentiate from the extensive frost damage that we saw recently. Begin scouting for beetles.
Beans & Peas – Peas are already in flower in several areas, and many beans have been planted.
Brassica Crops – Transplants are establishing well and putting up new leaves. If transplants have leaves cut off in the field around the soil line, dig around the plant and look for cutworm larvae (Figure 2B). It appears that cutworm damage is high this year. Wilted plants may be due to millipede (Figure 2A) or seedcorn maggot damage and if the leaves are purple, the wilt may be due to wirestem, caused by Rhizoctonia (Figure 2C). Adult click beetles and flea beetles are active and the first generation threshold for cabbage maggot emergence has been reached in Essex county.
Carrot – With the bulk of carrot acres seeded, many growers are irrigating to achieve good germination with the dry conditions that are being seen in some areas. With the stretch of hot weather, we saw a lot of heat canker and dying off from hot soil conditions despite frequent irrigation in some cases. Carrot weevil is active and laying eggs. There are reports of high black cutworm pressure this year from New York and some have been seen in Ontario. Monitor your fields for plants that look like they’ve been cut by scissors.
Celery – Aster leafhopper and tarnished plant bugs are active and thresholds have been reached in all regions.
Cucurbits – Large amounts of cucumbers have been planted, and pumpkin production is planned to proceed as per normal in Southwestern Ontario. Transplanted cucurbits were host to large emergences of striped cucumber beetle, so vine crops attractive to beetles such as zucchini, squash, and pumpkin should be scouted for these. It’s not too late to transplant trap crops such as zucchini or some squash cultivars: if you’d like a full list of varieties that make good cucumber beetle trap crops, email Andrew and he will send you one. Be on the lookout for herbicide injury due to warm temperatures in susceptible cultivars.
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 over the next 5-10 days. 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.
Leafy Greens – Cutworm pressure is higher than average this season 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 –The degree day threshold for onion maggot has been reached in most growing areas. Some onions showing signs of heat scald or herbicide damage. Control volunteer onions in neighbouring fields as this can be a source for fungi inoculum like Stemphylium (Figure 5) or pests like onion thrips. Black cutworms are active and can cause damage that looks like the onion has been cut with scissors above the soil line (Figure 6). Dig around suspect plants to look for cutworm larvae.
Potatoes – Almost all the potato acres are planted. Most of the early seeded acres weathered the frost surprisingly well and enjoyed that stretch of hot weather. There are reports of high black cutworm pressure this year so monitor for any plants that look like they’ve been cut off or chewed stems near the soil level. If you dig around in the top inch or two of soil near a damaged plant you can often find the cutworm larvae curled up. At-plant insecticides should be taking care of overwintering Colorado potato beetle adults. Monitor your fields and keep an eye on any Colorado potato beetle populations that appear to be multiplying earlier than expected. It is never too early scout for late blight as any infected seed piece could cause problems early.
Sweet Corn – sweet corn is progressing normally.
NOTE: Data as of June 3, 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: