VCR – Vegetable Crop Report – July 9th, 2026

Crop Updates

Asparagus – newly developing fern are very susceptible to foliar diseases. Scout for purple spot and rust. Fungicides act to prevent disease development; however product selection should be based on which diseases are present in the field. Both purple spot and rust first develop in the lower 24 inches of the fern. As the season progresses the lesions will mature and produce the spores that cause secondary infections on the fern. Fungicide coverage at this time targeting the lower canopy will help reduce secondary infections. Group 11 fungicides provide good purple spot control. Group 3 fungicides provide good rust control. Chlorothalonil (Bravo) is effective on both diseases, however the level of control is not as strong. It is a good rotational partner for resistance management and broad spectrum control.

Brassica Crops – The heat has dried out many regions which has led to many fields being irrigated. Conditions continue to be favourable for Alternaria and Sclerotinia white mould. Sclerotinia will start as 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. Once the crop is harvested, incorporate residue as soon as possible to reduce inoculum for future years. Managing chewing insects will also reduce the spread of Sclerotinia. Diamondback moths continue to be active in high numbers in many areas. In cabbage, keep an eye out for thrips as the heads start to form.

Carrots – Herbicide applications continue as the battle with pigweed rages on (Figure 1).

Cucurbits – The Michigan State University downy mildew spore trapping program continues to report positive air samples, however there are no active field infections reported in the Great Lakes region at this time. Infections typically appear in late-June to early-July each year. Cucumbers and cantaloupe are at the highest risk of developing downy mildew infections. Disease management programs for watermelon and cantaloupe should centre around the prevention of Alternaria and Anthracnose. In pumpkins and squash, powdery mildew is the primary pathogen of concern.

Garlic – Harvest has started in some regions. 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. When harvesting, remove bulbs from direct sunlight as soon as possible and be mindful of how long garlic is sitting in wagons/crates when there is no forced air present. Remove excess moisture from the crop as soon as possible as a slow cure will make it easier for pathogens to colonize wounds / bruises from harvest which will lower quality and the length of time the crop can be kept in storage. Be vigilant about reducing mechanical injury during harvest. When curing, controlling humidity is the most important variable to control. Curing over a long period of time (eg. 14+ days), can allow storage pathogens and bulb mites to acclimatize and cause problems in storage. Curing in a shortly period of time is less favourable for bulb mites which may result in a longer storage life. The higher the quality of crop that goes into storage, the longer it will last.

Onion – Seeded onions are starting to take off and so are the number of thrips. 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), Delegate (group 5), or Exirel (group 29). Entrust (group 5), Success (group 5), and Minecto Pro (groups 6 / 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. If you are in an area with long periods of leaf wetness with fog and/or morning dews, be on the lookout for downy mildew (Figure 2).

Figure 2. Downy mildew found in a community garden in Guelph – July 8, 2026.

Figure 3. Lacewing eggs. Lacewings are a natural predator of thrips and aphids – July 7, 2026.

Peppers – The cool spring made for a slow start for peppers and led to many growers seeing herbicide injury. With the warm weather the plants are now growing out of this injury and looking much healthier, though they are still about a week behind their typical growth stage. Bacterial disease is a concern for peppers as it has already been seen in some fields.

European corn borer has now completed its first peak flight. Growers should stay informed as the second peak will happen when the plants have fruit, and control measures will need to be taken. European corn borer larvae create a hole near the calyx of the pepper to enter the fruit and feed. Keep an eye out for frass (bug feces) on the top of the pepper fruit and inspect for entry holes. You can also use pheromone lures combined with halo traps to monitor for European corn borer adults. There are a number of insecticides options that can be added to the spray program for European corn borer control. Make sure to read all product labels thoroughly before every product application.

Potatoes – With the recent heat growers are seeing lots of symptoms of heat stress and air pollution including interveinal bleaching and brown leaf margins (Figure 4). Recently hatched eggs and Colorado Potato Beetle larvae (Figure 5) are still being found in fields. As most of the crop has filled the row and is flowering, there is little at-plant insecticide left in the plant. Pressure has been low-moderate and spotty so monitor for any large hotspots. Here is a list of registered products to use foliar against Colorado Potato Beetle. Some products should be targeted at younger larval stages so check the notes for instructions. If you applied a neonic seed treatment or in-furrow, do not follow up with a neonic (Group 4A) foliar.

Figure 4 – Brown leaf margins on a potato plant.

Figure 5 – Colorado potato beetle larvae at various lifestages feeding on a potato leaf.

Sweet corn – Over the past week there has been low-to-moderate risk of corn earworm migration into the Great Lakes region. Corn becomes attractive to the adult female moths during silking. Pheromone traps should be installed before silking and moved to fresh plantings when the silks begin to dry down.

Tomatoes – After a chilly start to the year setting growth back, tomatoes are not catching up and are approaching canopy closure. Bacterial disease is a concern for many growers and is widespread this year. Given the disease started during the cooler weather, it is likely bacterial speck, which the plants will outgrow. Bacterial spot, however, is likely also present now with the warm weather, and will continue to increase.

Growers should also be starting to scout for late blight. Though there have not been any reports in the Great Lakes region thus far, late blight typically starts to appear in mid-July. As soon as growers see late blight in a field, disease specific fungicides need to be added to the spray program to maintain control. Late blight is a community disease and spreads rapidly via wind. If growers see or suspect late blight, please report the incidence to OMAFA field staff. Make sure to read all product labels thoroughly before every pesticide application.

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***	879	788	540	400	238	618	788	339
Essex*	1320	1213	911	725	479	1009	1213	638
Chatham-Kent*	1237	1130	832	656	435	929	1130	578
Norfolk**	1135	1033	761	599	384	846	1033	522
Huron***	1024	926	660	506	314	744	926	437
Wellington**	981	889	641	493	306	718	889	425
Simcoe County***	1002	910	665	518	335	743	910	452
Durham***	1061	966	709	556	365	792	966	489
Peterborough	1008	914	663	516	323	744	914	447
Kemptville***	1078	985	722	570	378	806	985	503
Sudbury***	804	729	532	417	264	595	729	364
Timiskaming***	806	731	541	427	273	599	731	374
Lambton**	1125	1021	740	582	370	829	1021	508
Thunder Bay	661	589	403	301	166	459	589	254
Middlesex*	1151	1050	773	611	397	862	1050	535
Renfrew	904	823	598	472	316	670	823	418