VCR – Vegetable Crop Report – June 26th, 2025

Welcome back to the next VCR of 2025!

Currently most counties are trending close to their 10 year average GDD, with Bruce county trending slightly above their 10 year average.

Crop Updates

Brassica Crops – Diamondback moths and imported cabbageworms are common. No cabbage loopers have been reported yet. Dig up stunted plants and check for maggot damage. Check the growing points and undersides of leaves for aphids (Figure 1). Pull back cabbage leaves and look for thrips as populations are starting to climb. With rain in the forecast, be on the lookout for Alternaria over the next two weeks. In new transplants, continue to monitor for cutworms or heat canker. 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. To read more about black rot, refer to CropIPM. If you happen to come across black rot, please E-mail travis.cranmer@ontario.ca as we are looking for samples to use for a product efficacy trial that may lead to a new product registration.

Figure 1 – Characteristic V-shaped lesions of black rot on Brussels sprouts, caused by Xanthamonas campestris pv campestris.

Celery – Plants are establishing well. Aster leaf hoppers are active and in some fields the numbers are reaching the lower threshold of 10 leafhoppers/card. Scout and rogue plants showing yellow leaves/symptoms of aster yellows. It is unknown what percentage of aster leafhoppers may contain the aster yellows phytoplasma, but it is early in the season and the percent infected is likely to be low. If suspicious plants showing symptoms of aster yellows are found in or around the field, and the level of leafhoppers is high, it may be time for an insecticide application. Dig up stunted and/or wilted plants and inspect roots for nematode cysts, or carrot weevil larvae or if plants were unable to establish properly after transplanting due to a lack of adequate moisture.

Garlic – Most areas have finished scaping and plants with adequate moisture are bulbing up nicely. Many fields are showing leaf tips starting to senesce. Early season drought stress can lead to virus symptoms (such as tip dieback, stunting, mottling or streaking) to be more pronounced than in early in the season. Dig up plants showing yellowing of the leaves from the bottom upwards and inspect the bulb and basal plate. Yellowing of the lower leaves is generally associated with stem and bulb nematode (Figure 2), but it could also be Botrytis neck rot.

Figure 2 – Various degrees of stem and bulb nematode damage on garlic. Look for stunted plants with leaf yellowing from the bottom leaves of the plant moving upward.

Onions – Stemphylium leaf blight has been detected and has been observed in direct seeded onions as well as transplants. 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. The level of thrips continue to be low, but are likely to reach threshold within the next two weeks given the 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 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 crop 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.

Peppers – Peppers are having a bit of a tough year with the cold weather at planting. Peppers are very sensitive to night temperature 10°C or lower and soil temperature below 15°C. Many pepper growers who planted in late May and early June have seen chilling or frost injury. If the growing head of these peppers was still green and healthy, the plants should pull through. Check your plants again this week as the heat should help them grow more quickly. If significant growth in is not apparent, the peppers may not produce well this season. Growers should also be on the look-out for soil borne disease, which often pop up after a storm that causes standing water in the field. Removing water from the field quickly can help minimize the spr4ead of these diseases and spot treating particularly bad areas may be needed to help protect healthy plants. Soil borne disease can be hard to distinguish in their early stages. Look for dark drown to gray stem lesions, brown roots, or a spongy crown. Make sure to check soil moisture regularly and irrigate as needed to help prevent heat stress on pepper plants. If growers are concerned, they can always reach out to Amanda Tracey (519-350-7134) for assistance or advice.

Tomatoes – Tomato plants are growing quickly with the current heat wave. Growers should make sure to check soil moisture and irrigate as needed to ensure the plants are not affected by heat stress. With the heavy rains and storms that come with such intense heat, growers should ensure that water is removed from low lying areas as quickly as possible and keep an eye out for soil borne disease such as Phytophthora and Fusarium. Look first for wilting plants and then check for lesions on the stem at the soil line. Digging up wilting plants, growers should also look for unhealthy or brown root and a soft, spongy crown. If this occurs in a large area, spot treating is a registered fungicide could be beneficial to help minimize the spread to healthy plants. If growers are concerned, they can always reach out to Amanda Tracey (519-350-7134) for assistance or advice.

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***	724	642	423	307	171	490	642	257
Chatham-Kent*	962	865	603	460	284	683	865	395
Durham***	842	757	530	395	239	602	757	337
Essex*	1038	940	670	515	320	755	940	446
Huron***	824	735	505	380	234	575	735	328
Kemptville***	859	776	545	413	260	618	776	358
Lambton**	910	815	561	423	260	641	815	364
Middlesex**	946	854	600	455	285	680	854	393
Norfolk**	901	808	554	414	256	633	808	354
Peterborough	798	713	483	357	209	555	713	303
Renfrew	829	748	522	396	249	594	748	341
Simcoe***	796	711	489	363	223	558	711	312
Sudbury***	601	536	359	265	152	413	536	225
Thunder Bay	502	442	281	190	86	329	442	151
Timiskaming***	585	521	355	265	154	405	521	225
Wellington Centre**	805	719	490	364	220	563	719	311
Wellington North**	806	723	492	374	229	564	723	323