VCR – Vegetable Crop Report – July 25, 2024

Welcome back to the next VCR of 2024!

Almost all counties continue to trend above their 10 year average GDD, with the exception of Thunder Bay which is on trend with its 10 year average.

Crop Updates

Garlic – Harvest is underway. Pull bins out of the sun as soon as possible and ensure that the bulbs have good air circulation as soon as possible. Curing is complete when the bulb wrappers are crispy, the middle of the cut stem is hard, and the base of the stem is dry when cloves are removed. A shorter cure period focusing on reducing the relative humidity is key to avoiding bulb mites spreading pathogens over the next few months.

Onions – Conditions in some areas are still at high risk for onion downy mildew given the high humidity, heavy dews, and colder mornings. Stemphylium is progressing in many fields, especially those where the older leaves are senescing early due to excess moisture. As transplant fields are harvested, be sure to scout the edges bordering direct seeded fields. The second wave of onion maggots are active and causing damage in some onion growing regions.

Sweet corn – Heavy aphid populations have been identified in some sweet corn fields. High populations prior to tasseling are more concerning. Aphids, and the honey dew they produce on the tassels may prevent pollen shed. Populations on the silks may also inhibit pollination. Scout fields and take note of any populations before the tassel emerges from the whorl. If numbers increase over the next 5-7 days, a spray may be required to prevent barren cobs and/or prevent populations from developing on the husks. While scouting, look for beneficials including lady beetle adults and larvae, as well as lacewings and mummified aphids (caused by parasitic wasps). If populations are not too high, a healthy population of beneficials helps to keep aphids under control.

Fig. 1 – Lady beetle larvae on aphid infested sweet corn.

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***	1277	1157	834	640	389	935	1157	551
Chatham-Kent*	1604	1477	1123	914	616	1236	1477	810
Durham***	1456	1330	988	785	515	1096	1330	690
Essex*	1731	1598	1231	1010	702	1348	1598	905
Huron***	1394	1269	924	721	463	1034	1269	627
Kemptville***	1464	1340	1013	817	550	1115	1340	724
Lambton**	1574	1449	1096	885	602	1209	1449	785
Middlesex**	1586	1457	1099	887	599	1214	1457	787
Norfolk**	1534	1405	1045	836	552	1159	1405	737
Peterborough	1371	1248	916	716	458	1022	1248	625
Renfrew	1478	1356	1027	834	568	1131	1356	742
Simcoe***	1367	1246	915	716	458	1019	1246	621
Sudbury***	1178	1071	781	606	375	874	1071	523
Thunder Bay	963	860	585	430	230	670	860	358
Timiskaming***	1154	1053	772	602	379	862	1053	522
Wellington Centre**	1383	1258	926	728	464	1030	1258	635
Wellington North**	1361	1240	909	714	458	1014	1240	622