VCR – Vegetable Crop Report – July 11, 2024

Welcome back to the next VCR of 2024! Many counties experienced heavy precipitation over the last few days and all counties continue to trend above their 10 year average GDD.

Crop Updates

Brassica Crops – With all this moisture leading to extended periods of leaf wetness, be on the look out for Brassica downy mildew (Figure 1). Brassica downy mildew starts as yellow spots on the upper leaf surface with grey to whitish mycelial growth on the underside of the leaves. Avoid overhead irrigation or irrigate only in morning when plants are already moist due to the morning dew. Do not increase the leaf wetness period of the crop. Products registered for use on broccoli downy mildew can be found on the Ontario Crop Protection Hub. Dig up wilted plants to confirm the presence of clubroot (Figure 2), or cabbage maggot larvae.

**Figure 1**. Brassica downy mildew on a broccoli leaf – September 2023.

**Figure 2**. Swollen broccoli roots infected with clubroot.

Garlic – Harvest continues. Allow the crop to reach at least 40% yellowing/senescence before harvesting for better yields and increased storability. The ideal time for optimum yields is to harvest porcelain cultivars (such as Music) when 50% of the leaves have senesced or turned yellow. Since it takes several days to harvest, many growers start at 40% and by the time the crop is fully harvested it may have reached 70%. Always avoid leaving harvested bulbs in direct sunlight after they have been pulled. Curing / drying is often associated with an increase in temperature, however, when it comes to curing garlic, relative humidity should be the primary focus. Heating air increases the amount of moisture that the air can hold per cubic metre. A cubic meter of air can hold ~17 grams of water vapour at 20°C, while at 30°C it can hold ~30 grams. In most years, when the ambient air’s relative humidity is low, increasing the temperature greatly increases the water holding capacity of the air. This year, the air has been humid, and already close to being saturated. Therefore, increasing the temperature of the air will not add much more water holding capacity. As a result, it will take a longer amount of time to remove excess moisture from the crop. Speed up curing by adding dehumidifiers or air conditioners to pull as much moisture from the crop as quickly as possible.

Onions – Many direct seeded fields are at the 8-leaf stage and transplants are nearing maturity in some fields. Conditions in many areas have been favourable for onion downy mildew (Figures 3-5). While there are many products registered for onion downy mildew, past work by the Ontario Crops Research Centre – Bradford has shown that Orondis Ultra (groups 40/49), Zampro (groups 45/40) and Orondis Gold (Groups 4/49) are effective at protecting the crop against downy mildew. Despite the rain, the levels of thrips are climbing quickly in many fields. 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. Older leaves are turning yellow in fields that received excess moisture and some plants are showing signs of bacterial rot.

Figures 3-5. Leaves with downy mildew found on July 8^th in Wellington County.

Peppers – Peppers are progressing well, but a still a bit behind compared to the average year. Bacterial spot has worked its way into the province and is starting to show up in pepper fields. Using drip in stead of overhead irrigation can help to minimize the spread of bacterial spot in fields. There are also some Japanese beetles (Figure 6) migrating into pepper crops in search of food. These beetles can cause feeding damage on foliage, so keep an eye out for them in your crop. You can identify a Japanese beetle by their iridescent brown-green colour, a line of white dots along either side of their body and the three forked end of their antennae. Pheromone baited traps are available and can help bring numbers down when used properly.

**Figure 6.** Adult Japanese beetle on pepper plant

Tomatoes – Tomato crops are progressing nicely, though there are a number of disease concerns coming up right now. Most importantly, late blight (Figure 7) has been identified in Elgin (US-23 strain) and Kent (awaiting strain ID) counties.

**Figure 7.** Grey-brown late blight lesion on tomato leaf.

This is a community disease and if you see late blight in your field, please notify OMAFA staff. If late blight is found in your field or a neighbouring field, fungicides with specific late blight activity should be added to your fungicide program to prevent significant crop losses. Always be sure to read every product label carefully before each application.

Other disease concerns are phytophthora and fusarium, which have been causing pockets of wilting plants, and crown and root rot in many fields. Bacterial spot has also made its way into Ontario and is being seen in tomato fields. Using drip instead of overhead irrigation can help to minimize the spread of the disease within fields. Another pest to scout for at this time of year is stink bug. Stink bugs are thought to migrate into tomatoes as wheat is harvested. Look for adults (Figure 8) and nymphs (Figure 9) that like to hide deep in the plant canopy. Another way to scout for stink bugs is to look for the damage they cause like dimples (Figure 10) and light-coloured, snowflake patterns (Figure 11) on the fruit. Once stink bugs are found in your crop, you should follow a weekly spray program to keep numbers as low as possible. This is a very difficult pest to scout for and control. If you think you have a stink bug problem, please reach out to amanda.tracey@ontario.ca for information and guidance.

Figure 8. Adult stink bugs on tomato leaves

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***	1068	961	677	509	297	766	961	434
Chatham-Kent*	1182	1102	864	712	487	942	1102	636
Durham***	1196	1084	784	609	381	879	1084	528
Essex*	1482	1363	1034	839	571	1138	1363	747
Huron***	1158	1048	745	569	353	841	1048	489
Kemptville***	1222	1112	824	653	425	913	1112	574
Lambton**	1335	1223	909	724	480	1009	1223	637
Middlesex**	1287	1175	865	684	445	963	1175	601
Norfolk**	1301	1185	865	681	437	966	1185	595
Peterborough	1123	1014	724	553	336	816	1014	475
Renfrew	1217	1109	822	657	433	912	1109	579
Simcoe***	1145	1037	745	572	353	836	1037	490
Sudbury***	966	872	622	472	281	701	872	402
Thunder Bay	766	676	441	311	150	512	676	252
Timiskaming***	949	861	620	475	292	696	861	408
Wellington Centre**	1164	1052	759	587	361	850	1052	506
Wellington North**	1146	1037	745	577	360	838	1037	498