Temperature – Warm temperatures continued across the province this week with most growing regions now exceeding the 1000 degree day accumulation mark. Chatham, Essex and Norfolk have all continued to exceed their 10-year degree day accumulation average with Kemptville, Simcoe, and Wellington quickly approaching their respective averages. Remaining growing regions are still below their 10 year averages.
Rainfall – Precipitation in July was generally all over the place when comparing totals from region to region. The Chatham-Kent region received nearly 3 inches (75.4 mm) of rain on the 28th pushing it well past it’s 10-year average and receiving a total of 169.5 mm of rain for the month compared to a 10-year average of 90.8 mm. Norfolk nearly doubled its average for July receiving 121.4 mm of rain compared to a 10-year average of 69.7 mm of rain. Huron also marginally exceeded its 10-year rainfall average. Other growing regions ranged from marginally below to significantly below their averages with Simcoe county and Peterborough in particular receiving only a third of their monthly averages. Regular irrigation has been underway, especially in regions which have received little rainfall in the past month.
Brassica Crops – Continue to scout for Alternaria and incorporate all crop residue into the soil from a block once harvested.
Carrot – Canopies are generally closed in most fields. The second generation of Carrot Rust Fly is now active in Essex, Chatham, and Norfolk. Keep an eye out for leaf blights infecting the older leaves at the bottom of the canopy, as well as white mold in fields where the canopy has closed when scouting.
Celery – Celery leaf curl has been identified in several fields. Avoid walking through the fields when the humidity is high and the leaves are wet as celery leaf curl spores will stick to clothes and equipment. Carrot weevil damage as well as black heart (caused by a calcium deficiency) has also been observed.
Garlic – Harvest is underway in most areas of the province. Leek moth trap counts have come down in most fields. The third generation of leek moth will likely occur near the end of August and into September. After harvest, incorporate field debris to reduce the likelihood of leek moth completing it’s lifecycle.
Onions –Bacterial rot has been identified in both transplant and direct seeded fields. The weather has been conducive for Stemphylium development. The threshold for the second generation of onion maggot have been met in most growing region; affected plants will appear wilted with signs of feeding damage in or around the basal plate of the bulb. Feeding damage by yellow woollybear caterpillars has also been identified on hotspot plants in some fields (images below). Thrips pressure is low and most fields are still below the action threshold for thrips of 1 thrips/leaf. Conditions have not been favourable for downy mildew development in most onion growing areas of the province.
Potatoes – Continue to be vigilant in scouting for late blight, especially in irrigated areas as spores have been confirmed in spore traps found in Norfolk, Simcoe, Dufferin and Lambton counties. The closest confirmed plant infections found have been in Wisconsin. Early symptoms of late blight include water soaked lesions usually found on the lowest leaves near leaf tips or margins. Later infections will have dark brown or black lesions surrounded by a yellow halo, lesions will eventually coalesce together on both leaves and stems leading to plant collapse.
Corn Earworm: We are seeing increasing trap counts across the Great Lakes region. There were significant earworm flight from July 18-26th. Freshly silking corn is at high risk of infestation if earworm are active in the region. For the fresh market, if flights are sustained over the silking period, fields may require multiple applications to maintain quality. Pyrethroid resistance is common in corn earworm. Group 28 and Group 5 insecticides, provide a good rotation for resistance management purposes (image provided below)
Western Bean Cutworm: despite the late start to the year, WBCW moths still appear to be synchronized with the tasselling of field corn. WBCW typically prefer field corn which is at the tasselling to silking stage. They occasionally feed on sweet corn at the same stages, especially if there is a lack of suitable field corn in the area. Look for purple, spherical eggs. They are usually laid on the upper leaves in groups of 15-30.
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.