Temperature – All counties continue to trend at or slightly above their 10 year average GDD. Daytime temperatures are forecasted to remain in the high-teens or mid- to low-twenties and then rise towards the end of next week.
Precipitation – All regions received some precipitation over the last week with Norfolk, Huron and Simcoe counties well on their way to reaching their 10 year average already. Huron in particular received 52.8 mm of rain on Tuesday. Chatham-Kent, Durham and Peterborough have received approximately half of their 10 year average precipitation totals for June. Rain is forecasted over the weekend in most counties and then again towards the end of the week with the risk of thunderstorms in some regions.
Brassica Crops – Dig up wilted plants to inspect the roots for cabbage maggot larvae as larvae are likely to be actively feeding. Imported cabbageworm and diamondback moths are active and slug and cutworm damage has been observed (Figure 1). To determine if the threshold for management has been met for imported cabbageworm, diamondback moth or cabbage looper scout 5 plants in 5 locations and record the total number of each lepidopteran pest found (total number of egg or larvae found):
Diamondback moth x 0.2 = A
Imported cabbageworm x 0.5 = B
Cabbage looper x 1.0 = C
A+B+C and divide by 25 = Cabbage Looper Equivalent
For cabbage, the threshold is 0.3 and for broccoli and cauliflower the threshold is 0.2.
|Diamondback Moth||Imported Cabbageworm||Cabbage Looper|
|Eggs||-Scale-like eggs laid in small groups||-Yellow, bullet-shaped with ridges||-round, greenish-white|
|Larvae||-hairless||-Green larvae, short hairs, velvet-like appearance||-inchworms with thin white line along each side|
|Damage||-Create windows in leaves, do not consume through leaf||-Ragged holes and dark green frass not in piles||-Ragged holes and dark green frass in piles|
|Relative Damage (Cabbage Looper Equivalent)||0.2||0.5||1.0|
Celery – Transplants are establishing well. The thresholds for aster leafhopper and tarnished plant bug (Figure 2) has been reached across the province. Dig up wilted plants and inspect the roots/plug for cutworm larvae. Scout for carrot weevils as they may be emerging around the field borders.
Garlic – Fall-planted garlic have reached their max number of leaves for the season. The number of adult leek moths trapped has been very low over the past two weeks and it is likely that the second flight will be occurring shortly. Target the next wave of leek moth larvae a week after the next peak of adults trapped. Scapes are emerging emerge across Ontario. Be on the lookout for leek moth feeding damage and kill any larvae or cocoon that you observe while scaping. Cut scapes of hardneck cultivars as soon as possible for the greatest yield benefit. Avoid using sickle bar mowers to remove scapes as they can easily spread garlic pathogens (including viruses) and often clip leaves during the scape removal process. Snapping the scape, by hand, an inch above the youngest leaf is ideal. Pulling scapes instead of snapping can cause the upper leaves to lose support and fall over causing pre-mature senesce of the plant. Past research has shown that by accidentally removing one leaf when the scape was removed, bulb sizes were reduced by 13% and the yield was reduced by an average of 17.5%. The same trial showed that yield was greatly impacted as the number of leaves cut during mowing increased. If the top two leaves were cut, the yield was reduced by approximately 25%, almost outweighing any potential gains you would expect by removing the scape in the first place. Avoid applying any nitrogen past the 5th leaf stage as this has been found to decrease storage life and cause ‘rough’ bulbs with cloves forming outside the main bulb wrapper.
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.
Onions – Many direct seeded onions have reached the fourth leaf stage and some areas are even a little further along. Scout for onion smut, onion maggot and cutworm damage. The pressure of thrips is low in direct seeded fields, however, it will likely increase dramatically as we see more hot and dry weather. Past research has shown that Movento 240 SC (group 23) has some residual activity that works better against larvae when it is applied earlier in the season. If the spray threshold exceeds 3 thrips/leaf, Movento 240 SC could be followed by two applications of Delegate (group 5) or Agri-Mek (group 6). Using a penetrating surfactant can be useful to maximize the effectiveness of products against thrips. Apply no more than two consecutive insecticides from the same IRAC group as thrips have a relatively short life cycle with multiple generations through the summer months and are at a high risk of developing insecticide resistance.
Pest Degree Day Forecasting
*NOTE: Data as of June 8, 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: