VCR – Vegetable Crop Report – September 4th

Weather Update

Many regions have recently fallen below their 10-year average in growing degree days as things start to cool off and become wetter.

Recent storms pushed August rainfall above the 10-year average in most regions, with some receiving more than double the average. September has also started wet, with many regions already receiving 20 to 30 mm (0.8 to 1.2 inches) of rain and locally higher amounts.

For more specific data see below for a list of regions and counties

Crop Updates

Brassica Crops – Conditions continue to be very favourable for many fungal and bacterial pathogens including Alternaria, black rot, downy mildew and sclerotinia. Numbers of aphids, diamondback moths and tarnished plant bugs continue to be high in multiple regions. Slug damage around field borders is also prevalent in some fields (Figures 1-2).

**Figure 1** – Slug feeding on a broccoli leaf.

**Figure 2** – Slug feeding on the leaf of a Brussels sprouts.

Garlic – Planting season has started. Cloves should be planted within 7 days of cracking to ensure vigour and best chance of overwintering survival. If Fusarium basal rot was an issue this past season, consider following:

Follow a long crop rotation; aim for 7 or more years before returning to the same field
Use planting stock with intact basal plates and looks disease-free
Avoid planting garlic in fields that were wheat or sorghum Sudan grass was grown the previous season as there is some evidence that Fusarium species that colonize garlic are also a host in these crops (Fusarium proliferatum in wheat and Fusarium oxysporum in Sorghum Sudan grass)
Consider planting in raised beds if the field is likely to be saturated with water at any point during the growing season
Plant cloves after cracking as soon as possible and avoid planting anything that was split over 7 days ago

If you are still considering purchasing new planting stock for the 2026-2027 field season, remember that low levels of stem and bulb nematodes can be found in planting stock. Testing one bulb for every 200 lbs of planting stock or one in every 1000 bulbs could be a good indication of if there are nematodes present. Along with avoiding stem and bulb nematode, here are some other things to consider before purchasing new planting stock: https://onvegetables.com/2022/08/05/garlicplanting/.

Onions – Harvest has been postponed in many areas due to the rain events over the past week.

Potatoes – With the recent storms, weather has been ideal for a number of diseases but especially Late blight. Multiple regions (New York, Eastern Ontario (home garden), Quebec (earlier in the season), and Michigan) have now reported the presence of late blight at some point this season so risk is considered high for later harvested potatoes. Registered products can be found at this link. Wet harvest conditions also raise the risk of Pink rot, Soft rots and Pythium leak.

If you grew Colomba this season, did you see symptoms like those in the pictures below? In order to determine the extent, investigate some possible causes and find solutions, I’m interested in hearing from you. (contact: Dennis Van Dyk – 519-766-5337)

Snap Beans – be on the look out for two spotted spider mites. They often appear in the field edges along side dusty laneways or gravel roads. The symptoms are very subtle, until they aren’t! Look for yellowing between the leaf veins accompanied by bronze-to-brown stippling. Dirt will often stick to the lower leaf surface where the mites have left webbing. The mites themselves are very difficult to see with the naked eye and may require a 10x hand lens to confirm they are there. The following article outlines the current status of miticide resistance in Ontario as well as the identification of new species of mites feeding in beans.
Spider Mites Active in Some Fields – Scouting is Advised – Field Crop News

Two Spotted Spider Mite – lower leaf surface

Sweet Corn – the recent storm activity puts sweet corn at higher risk of infestation by corn earworm, especially as trap counts in the mid-west have recently spiked. If you are trapping for corn earworm on your farm, consider reporting the findings to the Great Lakes and Maritimes Pest Monitoring Network. All corn at the green silk stage is attractive to egg-laying females.

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 below
Bruce***	1777	1630	1214	962	632	1348	1630	845
Essex*	2427	2263	1790	1490	1073	1944	2263	1345
Chatham-Kent*	2254	2091	1625	1336	948	1778	2091	1203
Norfolk**	2053	1897	1462	1192	816	1601	1897	1062
Huron***	1945	1791	1356	1091	731	1497	1791	966
Wellington**	1882	1734	1318	1058	703	1451	1734	934
Simcoe County***	1926	1778	1366	1106	755	1500	1778	984
Durham***	2039	1888	1463	1197	839	1601	1888	1074
Peterborough	1918	1769	1350	1090	729	1487	1769	966
Kemptville***	2029	1881	1452	1191	834	1591	1881	1068
Sudbury***	1682	1551	1187	960	638	1305	1551	850
Timiskaming***	1641	1510	1152	926	604	1266	1510	817
Lambton**	2154	1994	1545	1275	895	1690	1994	1145
Thunder Bay	1534	1405	1052	838	534	1164	1405	734
Middlesex*	2159	2002	1557	1283	901	1702	2002	1151
Renfrew	1754	1625	1256	1034	734	1376	1625	932