VCR – Vegetable Crop Report – July 6th, 2023

Welcome back to the Vegetable Crop Report! As the first week of July comes to an end, we are beginning to see slow starts to our precipitation averages for most counties.

Brassica Crops – Rapid growth due to heat and excess moisture may lead to nutrient deficiencies, tip burn and hollow stem in broccoli over the next couple of weeks. These abiotic disorders often vary by cultivar in their severity. Alternaria is active and early detection and management of Alternaria will reduce potential inoculum later in the season. Incorporate all left over plant tissue immediately after harvest to lower the amount of inoculum available to infect later plantings. Continue to scout for lepidopteran pests, aphids and thrips. Thresholds for lepidopteran pests using the cabbage looper equivalent can be found here: https://onvegetables.com/2023/06/15/vcr2023-07/

Garlic – Harvest is quickly approaching and some fields are quickly senescing if they are overly stressed. Allow the crop to reach at least 40% yellowing/senesce before harvesting for better yields and increased storability. Symptoms of Fusarium basal rot, Botrytis neck rot and stem and bulb nematode will cause pre-mature senesce (Figure 1). Depending on how quickly your soil dries out, avoid irrigating too close to harvest as soil stuck to the bulb will make it more difficult to achieve a clean wrapper. If black plastic has been used for weed control, cutting it open to allow the soil to dry before harvest can also help with wrapper cleaning. If leek moth counts were high last week, consider targeting the larvae that are now feeding on the crop. If mites or Fusarium were issues in storage last year, refer to this article with information about curing: https://onvegetables.com/2021/12/09/stored-garlic-might-have-mites/

**Figure 1**– Infected plants with Botrytis neck rot appear stunted and green leaves can develop water-soaked lesions, wilt and eventually turn yellow (A). Plants infected with stem and bulb nematode show similar symptoms with yellowing of the leaves from the bottom of the plant moving upward, but the leaves turn yellow before wilting (B).

Onions – Stemphylium has been observed in multiple fields across the province. Conditions have been favourable for white rot development. There are no pesticides that are registered to control white rot. The best management strategy is prevention as spores can persist in the soil for at least 40 years. If only a few plants are observed, rogueing out plants in these affected areas (Figure 2). The high humidity, heavy dews and colder mornings means that conditions may have been favourable for onion downy mildew in several areas across the province (Figure 3). The 2017 Muck Vegetable Cultivar Trial & Research Report from the Ontario Crops Research Centre – Bradford summarizes downy mildew product efficacy on page 66: Click here to visit page 66 of the 2017 report. Past research has shown Orondis Ultra (groups 40/49), Zampro (groups 45/40) and Ridomil Gold MZ (groups 4/M3) to be effective for downy mildew management when they are applied as a protective application, before infection. A full list of products registered for downy mildew on dry bulb onion can be found here: Onion x Downy Mildew – Ontario Crop Protection Hub

**Figure 2**– White rot mycelium growing on onion bulb with black sclerotia present – July 2022.

**Figure 3**– Onion downy mildew will start as a tan lesion with purple-grey, velvety growth. Diseased leaves turn pale-green, yellow, and then collapse. Usually starts as a small patch then quickly spreads throughout the field – August 2019.

Tomatoes and Eggplants – Colorado potato beetle continues to be a concern for some growers. Two foliar applications of registered insecticides are recommend 5 days apart to ensure that newly hatched larva are also being targeted. Always read all product labels thoroughly before any pesticide application.

Growers should also be aware that early blight spores have been detected on spore traps across southwestern Ontario. Keeping up on a good general fungicide program should protect most crops, but be on the lookout for key symptoms, like foliar lesions with concentric rings, in your fields (Figure 4).

**Figure 4**– Early Blight on Tomato Plant

Pest Degree Day Forecasting

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
Bruce***	857	774	543	406	244	617	774	349
Essex*	1143	1038	759	603	391	845	1038	530
Chatham-Kent*	1065	964	697	545	343	781	964	475
Norfolk**	1045	945	685	535	336	766	945	464
Huron***	937	844	604	462	280	679	844	395
Wellington**	935	848	614	472	292	688	848	408
Simcoe County***	932	844	602	465	287	678	844	402
Durham***	1007	913	660	517	327	738	913	451
Peterborough	942	852	602	458	275	680	852	394
Kemptville***	1014	924	675	524	329	755	924	453
Sudbury***	871	793	576	446	282	646	793	387
Timiskaming***	849	771	549	419	262	621	771	361
Lambton**	1014	916	653	506	311	736	916	437
Thunder Bay	715	642	442	332	189	506	642	281
Middlesex*	1052	955	700	549	347	779	955	480
Renfrew	1011	923	677	528	337	757	923	461