VCR – Vegetable Crop Report – August 15th, 2025

Welcome back to the next VCR of 2025!

Currently most counties are slightly above their 10 year average GDD, with Norfolk, Sudbury, Timiskaming, and Thunder Bay trending at their 10 year average.

Crop Updates

Brassica Crops – Transplanting for late broccoli has finished. Alternaria is starting to show in some fields. Alternaria can cause head rot in broccoli and cauliflower if spores are able to infect the beads/curds and secondary bacteria can cause rot. With the hot and dry weather, be on the lookout for symptoms of black rot –Xanthamonas campestris pv. campestris (Figure 1). Black rot spreads rapidly during warm weather and fields with overhead irrigation. The bacterial cells enter 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.

https://i0.wp.com/onvegetables.com/wp-content/uploads/2022/06/CH7_BRA_Fig7-03a-BlackrotLeafOnCauliflower.jpg?ssl=1 — **Figure 1** – Black rot leaf on cauliflower with characteristic ‘V’ shaped lesion on leaf tip.

Garlic – Stained bulb wrappers on bulbs headed to storage may be due to Pseudomonas (Figure 2). To reduce symptoms of Pseudomonas next year;

Shorten cure time by removing excess moisture from the crop as quickly as possible using dehumidifiers
Rogue out cloves with missing bulb wrappers, brown streaking or fat necks and do not use them as planting stock
Avoid poorly drained fields and plant in raised beds if there are concerns of flooding in any part of the growing season
Avoid planting in headlands or areas that are in the shade; shade results in extended periods of leaf wetness periods which result in better conditions for bacterial development
Implement a 4-year crop rotation
Avoid overhead irrigation; utilize drip irrigation instead
Avoid applications of nitrogen after the 5^th leaf stage

**Figure 2** – Brown streaking of *Pseudomonas cedrina* – Photo by R.A.G. 2024.

**Figure 3** – Decaying bulb wrappers of *Pseudomonas marginalis* – 2021.

**Figure 4** – Internal bulb rot of *Pseudomonas fluorescens* – 2024.

Onion – Transplants continue to be harvested and direct seeded onions are starting to lodge. Stemphylium leaf blight and tipburn is starting to take hold in direct seeded fields but the level of Stemphylium lesions to other years is lower. Royal MH can be applied for sprout control when 50% of the crop has lodged and there are green tops that are still present to absorb the product. Apply at least 10 days before the crop is harvested. Now is a great time to assess damage plots that were put up in the spring. Determining the number of plants that survived out of the 100 germinated/transplanted plants that were counted at the start of the season is valuable information to determine what percentage of plants died due to onion maggot, drought, or some other pest.

Peppers – Phytophthora remains a concern for pepper growers even though the season has been dry and generally not conducive to disease development. Check wilting plants for crown and stem lesions and brown, unhealthy roots. Affected areas of the field can be tilled under to help minimize the spread of fresh spores. We are also approaching the final peak of European corn borer (ECB) in most areas of the province and have reached the beginning of the final peak in Essex County. Growers should be gearing up to spray an insecticide to protect fruit. FRAC group 28 and 3A products are a good option for ECB control in peppers.

Tomatoes – Tomatoes are looking very good in most growing regions of the province. Early varieties are ready for harvest which will begin on August 15th. On August 7, 2025 late blight was observed in tomatoes in Middlesex county Ontario. Growers should remain aware of the risk in the area by staying up to date on blog posts. Growers should continue with their general fungicide program and consider late blight specific fungicides only if there are symptoms in the field or in a field very nearby.

Phytophthora capsici is still a concern in most growing areas in Southwestern Ontario. Growers should be on the look out for wilting plants, buckeye rot on green fruit and red fruit turning into “water balloons”, especially in lower areas of the fields. There are some control options that can help to protect the remaining fruit.

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***	1583	1451	1082	865	580	1199	1451	766
Chatham-Kent*	1935	1789	1376	1133	807	1506	1789	1018
Durham***	1804	1669	1291	1057	750	1414	1669	948
Essex*	2057	1909	1489	1235	889	1624	1909	1115
Huron***	1723	1585	1204	980	683	1325	1585	877
Kemptville***	1797	1663	1283	1050	748	1406	1663	945
Lambton**	1882	1737	1333	1095	781	1463	1737	986
Middlesex**	1901	1758	1355	1110	789	1484	1758	997
Norfolk**	1831	1688	1284	1044	734	1413	1688	934
Peterborough	1702	1567	1187	961	663	1309	1567	857
Renfrew	1805	1674	1299	1072	775	1421	1674	968
Simcoe***	1728	1593	1221	995	705	1340	1593	894
Sudbury***	1417	1303	979	787	527	1083	1303	698
Thunder Bay	1278	1167	856	665	412	954	1167	576
Timiskaming***	1382	1268	952	763	502	1053	1268	673
Wellington Centre**	1687	1551	1172	946	652	1295	1551	843
Wellington North**	1681	1548	1171	955	663	1291	1548	854