VCR – Vegetable Crop Report – June 25th, 2026

Crop Updates

Brassica Crops – 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. Diamondback moths and imported cabbageworms are common. No cabbage loopers have been reported yet. Continue to scout for lepidopteran pests. Thresholds for lepidopteran pests using the cabbage looper equivalent can be found here: https://onvegetables.com/2026/06/11/6/. Check the undersides of leaves for aphids and pull back cabbage leaves to look for thrips. Be on the lookout for black rot, caused by the pathogen Xanthamonas campestris pv campestris (Figure 1). Black rot spreads rapidly during warm, humid weather and enters other plants through wounds or natural openings on the leaf tips. The Xanthamonas bacteria often finds it’s way to farms in infected seeds and then bacterial cells overwinter on used trays, propagation equipment, and crop debris for up to three years. Infected plants have characteristic ‘v’ shaped lesions and systemically infected plants have chlorotic areas anywhere on the leaf. When leaves are held up to the sun, veins filled with Xanthamonas bacteria are stained black in the chlorotic areas on the leaf. The best management strategy is prevention through certified clean seed, sanitation of propagation equipment/tools, a four-year crop rotation, and rogueing and then burying all crop debris. With the excessive moisture in some regions of the province, fields with clubroot will likely start to show symptoms on susceptible plants. Blind plants are becoming more noticeable as the surrounding plants gain height. Plant missing a primary growing point (blind plants), is potentially due to Swede midge damage that may have occurred a few weeks ago (Figure 2).

**Figure 1** – Black rot can cause characteristic ‘v’ shaped lesions on infected plants.

**Figure 2** – A blind Brussels sprouts plant missing a primary growing point, potentially due to Swede midge damage that occurred a few weeks ago. June 22, 2026.

Carrots – With many fields in the 2-6 leaf stage, this is an important time for carrot weevil applications if your pressure is high. Here is a list of products registered for carrot weevil.

We are also nearing the stage when applications for Aster leafhopper are needed to prevent Aster yellows later in the season. Aster leafhopper infectivity testing from Michigan is showing lower infectivity counts to start the season.

It is also an important time for weed control. If you are on muck soil, Zidua was recently registered which can help with redroot pigweed. Zidua has pre-emergent weed activity and it is applied around the 2-3 leaf stage.

Garlic – Harvest is around 2-3 weeks away in most fields that are growing Music or a similar hardneck cultivar. Allow the crop to reach at least 40% yellowing/senesce before harvesting for better yields and increased storability. Harvesting early will maximize the amount of bulb wrappers present while later harvests will result in fewer bulb wrappers available to brush off and allow for a marketable bulb. Symptoms of Fusarium basal rot, Botrytis neck rot and stem and bulb nematode will cause pre-mature senesce (Figure 3). 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 trimming and wrapper cleaning. If leek moth counts were high last week, consider targeting the larvae that are now feeding on the crop. If bulb 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 3** – 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 is active has been observed in seeded and transplant onion fields across the province (Figure 4). If Penflufen was part of the seed treatment, do not start with a foliar group 7 fungicide. For the first application, a product containing mancozeb (group M3s, such as Manzate Pro-Stick, Dithane Rainshield, and Penncozeb 75 DF Raincoat) may provide protection against Stemphylium if it is being applied to manage onion smut, Botrytis or Alternaria/Purple Blotch. Avoid applying products from the same chemical group one after the other to manage Stemphylium. For the second foliar product, Allegro 500F (group 29) or products containing a group 7 show the best efficacy, such as Sercadis, Aprovia, or Miravis Duo (group 7/3). Research has shown that there is very high resistance in Stemphylium to one of the fungicides in Quadris Top (group 11/3) and in Luna Tranquility (group 7/9). Avoid applying products from the same chemical group one after the other to reduce the selection pressure against group 7 or group 29 fungicides so that they can be used to manage Stemphylium for future years. Botrytis lesions have also been found but fungicides applied against Stemphylium will likely suppress any Botrytis in commercial fields. The level of thrips (Figure 5) continues to be low, but they are active and are likely to reach threshold next week as the daily temperature begins to climb. 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 as the first insecticide. Once the threshold of thrips/leaf has been reached, Movento 240 SC (two applications) could be followed by two applications of Agri-Mek (group 6) or Delegate (group 5). Entrust (group 5), Success (group 5), and Exirel (group 28) are also registered for thrips on onions. 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.

**Figure 4** – What appears to be the start of a Stemphylium lesion on a direct seeded onion. June 24, 2026.

**Figure 5** – Thrips on a direct seeded onion. June 24, 2026.

Potatoes – Many fields in Norfolk County are starting to flower, many fields in the Alliston area are filling the rows and starting bud formation. With lots of new growth and some recent storms rolling through the area, disease and fungicide applications should be top of mind. Ensure new growth is protected. No late blight has been reported in any region in North America to this point in the season but continue to monitor for symptoms (Figure 6). To see a list of registered fungicides for early and late blight, visit the Ontario Crop Protection Hub: Potatoes – Early blight and Late blight fungicides. There is also a crop risk tool available to assess your risk of late blight and early blight which you can find here: Crop Risk Tool

**Figure 6** – Potato late blight lesions.

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***	632	556	349	237	117	413	556	190
Essex*	1065	970	704	542	332	790	970	467
Chatham-Kent*	954	861	605	457	278	688	861	393
Norfolk**	861	773	543	408	236	614	773	346
Huron***	758	674	450	324	174	520	674	269
Wellington**	729	650	443	322	176	507	650	268
Simcoe County***	733	655	453	333	192	517	655	281
Durham***	792	711	496	371	222	564	711	317
Peterborough	747	667	459	339	188	525	667	285
Kemptville***	811	732	510	387	237	580	732	333
Sudbury***	569	507	349	260	146	399	507	219
Timiskaming***	564	503	355	269	157	399	503	230
Lambton**	848	758	519	390	220	594	758	330
Thunder Bay	449	390	247	173	80	289	390	139
Middlesex*	864	777	542	408	236	616	777	346
Renfrew	689	619	426	322	200	488	619	280