VCR – Vegetable Crop Report – July 26, 2019

Ontario DD Map - July 26

Temperature – Hot and humid temperatures have returned after a brief reprieve from the hot weather earlier this week in most growing regions of the province. Chatham, Essex, and Norfolk counties have all caught up to their 10-year average degree day accumulations while the remaining growing regions are still marginally to significantly behind their 10-year norms.

Rainfall – Precipitation has been sporadic in most growing regions with most regions receiving between 10 and 30 mm of rain within the past week. The remaining growing regions range from being well below, to on track with their monthly rainfall norms. Average monthly rainfall totals have been exceeded in Norfolk county, with Huron and Wellington counties quickly approaching their respective averages. Remaining growing regions range from a quarter to three quarters of their average rainfall totals for the month. Regular field irrigation is underway in most regions, especially those who’ve received little to no rain in the past two weeks.

Crop Updates

Brassica Crops – Diamondback moths, flea beetles, aphids and imported cabbageworm are prevalent in many fields. Continue to scout for Alternaria and incorporate all crop residue into the soil from a block once harvested.

Carrot – Canopies are beginning to, or are already closed in many fields. Threshold has been met for the second generation of Carrot Rust Fly in Essex County and will likely be met in Chatham, Norfolk, and Kemptville within the next week.

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 many parts of the province. Hardneck cultivars like Music are generally harvested when 40-60% of the leaves have senesced and turned yellow. Once harvested, try to keep bulbs out of direct sunlight as research has shown that this will increase storage life. 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.

Onions –The heat from last week may have led to an increase in the incidence of bacterial rot in onions, especially in irrigated fields. Onion maggot damage, onion smut, pink root, and stemphylium are also present. 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. Many fields are still below the 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 – Despite the hot weather this week, be vigilant in scouting for late blight, especially in irrigated areas as spores have been confirmed in multiple spore traps in the province. 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. Early blight infection is also still showing up in some fields typically on older leaves. During this time of rapid growth, remain vigilant in both scouting and fungicide applications to ensure new leaves are protected. We are still seeing Colorado potato beetle larvae at various growth stages which have hatched and began feeding on plants. Remember to rotate insecticide groups for any foliar applications. We are still looking for some samples to test for insecticide resistance so if you have some CPB feeding in your fields, please contact Dennis at 519-766-5337. With the hot and dry conditions we’ve had the last week or two, it’s important to maintain soil moisture levels during critical growth stages. Refer to the chart below for the impact of dry weather on yield loss.

Growth Stage	Soil Available Water Requirement	Yield Losses IF Available Water Below Required Levels
Growth Stage I Sprout Development	75% available soil water	Short periods of drought stress do no reduce yields
Growth Stage II Vegetative Growth	75% available soil water	5%
Growth Stage III Tuber Initiation	80% available soil water	10%
Growth Stage III Tuber Initiation	80% available soil water	10%
Growth Stage IV Tuber Bulking	90% available soil water	40-60% Highest demand for water. Adequate water is necessary for high yield. Dry conditions favour tuber malformations
Growth Stage V Tuber Maturation	60-65% available soil water	Water deficit causes tuber dehydration

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
Essex*	1545	1421	1079	877	614	1189	1421	781
Chatham-Kent*	1397	1275	946	749	475	1050	1275	660
Norfolk**	1369	1253	932	741	468	1035	1253	654
Huron***	1129	1020	726	553	316	817	1020	475
Wellington**	1173	1066	771	601	364	864	1066	526
Simcoe County***	1155	1047	755	587	355	847	1047	513
Durham***	1225	1117	825	659	417	916	1117	582
Peterborough	1105	996	700	527	297	794	996	452
Kemptville***	1261	1152	856	676	417	950	1152	591
Sudbury***	1010	916	664	519	311	742	916	454