VCR – Vegetable Crop Report – July 2nd, 2026

Crop Updates

Brassica – High temperatures this week will increase the chances of seeing nutrient deficiencies, tip burn in Brassicas as well as riciness in cauliflower and brown bead, bolting, and hollow stem in broccoli over the next two weeks (Figure 1). 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. Avoid increasing the leaf wetness period of the crop by irrigating only in the morning when plants are already moist due to the morning dew. With the hot and wet weather, be on the look out for Sclerotinia/white mould. Sclerotinia mould tends to start near the ground on plants and as it infects it creates dark, water-soaked areas on the lower leaves near the base at the soil line. As the pathogen progresses you may see white mycelial growth. These water-soaked lesions enlarge and can cause the leaves to wilt. Infected cabbage heads will retain their shape but will be filled with a soft, watery rot. If conditions are favourable for the Sclerotinia, you will see the white mycelial growth followed by small, black spots/spores that look like mouse droppings within the fluffy white growth. These black spores can overwinter in the soil for up to 8 years and the best preventative management strategy is to rotate with non-susceptible crops such as beets, onions, spinach, corn, cereals, or grasses. It is also helpful to decrease the plant density of the field to allow for adequate air circulation. Allow the top inch of soil to dry out between irrigation events and incorporate residue from harvested areas as deep as possible. Continue to scout for lepidopteran pests, aphids, and thrips.

**Figure 1**. Broccoli beads turn brown from extreme fluctuations in soil moisture and temperature.

Carrots – Irrigate where available to lower soil temperatures and reduce losses to heat canker (Figures 2-3).

Garlic – Many fields with heavier soils are showing witches brooming this year which was likely caused due to extended periods of saturated soils. While there may not have been standing water in these fields in the past few months, there were extended periods where the top layer of soil was consistently wet for a significant duration of time. This excess moisture may have resulted in the plant growing extra cloves outside of the main bulb and as these cloves are forming, their leaves are extending up the stem and emerging at the same place where the scape emerged. Depending on where these extra cloves are forming, some plants may produce unmarketable bulbs. Stemphylium and Alternaria are starting to colonize the yellowing tips in many fields, and some fields are showing lesions where water may have been sitting where the leaf attaches the stem (Figures 4-5). While this fungus can infect healthy leaves, Stemphylium easily infects dying or dead leaf tissue. Fusarium basal rot is also prevalent this year, and it can easily be confused with stem and bulb nematode damage (Figure 6). In bulbs infected with Fusarium basal rot, some roots will stay on sections of the basal plate while in plants infected with stem and bulb nematode, all roots may completely detach from the basal plate (Figure 7). To know for certain that it is only Fusarium basal rot and that there are no nematodes present, submit a sample to a pathogen diagnostic clinic to test for stem and bulb nematode. Harvest is one to two weeks away and some fields are quickly senescing if they are overly stressed. For better yields and storability, allow the crop to reach at least 40% yellowing/senesce before harvesting. Since it generally takes several days to harvest the entire crop, many growers start at 40% and by the time the crop is fully harvested it may have reached 60 or 70%. The ideal time to harvest for porcelain cultivars (such as Music) is when 50% of the leaves have senesced or turned yellow. 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. Always avoid leaving harvested bulbs in direct sunlight after they have been pulled. Focus on curing the crop quickly if Fusarium or mites have been a problem in the past: https://onvegetables.com/2021/12/09/stored-garlic-might-have-mites/

**Figure 4**. Stemphylium lesions forming where the leaves attach to the stem.

**Figure 5**. Stemphylium spores isolated from these older leaves on a plant stunted by Fusarium basal rot.

**Figure 6**. Plant stunted due to Fusarium basal rot (this plant was dug and sent to a diagnostic clinic).

**Figure 7**. Fusarium basal rot (not nematodes) causing the loss of roots and symptoms of rot at the basal plate.

Onion – Transplant onions are looking great, and many direct seeded fields are at the 6-7 leaf stage. Onion maggot has reached it’s second degree-day threshold and is likely active in Essex and will be shortly in the other major onion growing regions. The levels of thrips are starting to rise. Play close attention to fields bordering hay and wheat as the levels of thrips will generally start to increase as hay is cut and wheat is harvested. Apply no more two applications of the same insecticide targeting thrips for resistance management. Stemphylium is starting to colonize the tip dieback in many fields (Figure 8). If Penflufen was part of the seed treatment, do not start a foliar fungicide program with a group 7 fungicide. For the first application to manage Stemphylium, 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.

**Figure 8**. Tip dieback on direct seeded onions – June 24, 2026.

Potatoes – This hot weather puts the crop under a lot of stress. This is the time where soil borne diseases that are limiting the crop start to show symptoms. These include Rhizoctonia, blackleg, Potato Early Dying (PED), Verticillium wilt and Potato Virus Y. If you have the ability to irrigate, now is a good time to relieve some crop stress at a critical development stage.

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***	751	668	441	314	173	511	668	260
Essex*	1208	1106	818	642	412	911	1106	560
Chatham-Kent*	1088	988	711	548	349	800	988	478
Norfolk**	988	893	642	494	300	720	893	424
Huron***	882	791	546	406	235	624	791	344
Wellington**	842	757	530	396	230	600	757	335
Simcoe County***	859	775	551	417	255	622	775	358
Durham***	920	832	595	456	287	671	832	396
Peterborough	872	786	556	422	250	630	786	361
Kemptville***	939	853	611	473	302	688	853	413
Sudbury***	675	607	431	330	198	487	607	283
Timiskaming***	686	617	448	348	215	499	617	302
Lambton**	977	880	620	476	285	702	880	409
Thunder Bay	546	481	316	228	114	365	481	188
Middlesex*	997	903	647	499	306	728	903	430
Renfrew	800	724	513	398	257	581	724	349