VCR – Vegetable Crop Report – May 19th, 2023

Welcome back to the VCR Report for 2023!

Brassica Crops – Plants are establishing well, and transplanting continues across the province. Diamondback moth has already been identified in Chatham-Kent, and imported cabbageworms are active in most counties. The nighttime lows have generally been above temperatures that would result in frost damage in head brassicas in most regions. In areas with hard frosts, plants may see older, outer-most leaves turn yellow and wilt over the next week. Plants that were not properly hardened off before transplant are at a greater risk of frost damage. It has not been warm enough for the first generation of cabbage maggot to reach its threshold in any county, however, adult flies are likely around in low numbers in more-protected areas. Dig up wilted plants and inspect the roots for wireworm or millipede damage.

Garlic – Cool nights have led to many fields showing yellow tips on older leaves, despite whether herbicides have been applied in the past. Leek moths have been captured in most areas across the province. Leek moths can be monitored to inform insecticide timing by using Delta 1 traps and more information can be found here: May 17, 2023 ONVeg article. Dig up wilted plants and look for Delia maggot larvae (Figure 1).

**Figure 1.** Stunted garlic plant with Delia maggot fly larvae – May 14, 2020.

Onion – Most fields have been dried enough for the majority of transplants and direct seeded onions to be transplanted. Cooler nights have made it difficult for transplants to get established. Onion maggot flies have reached their threshold for the first-generation emergence in most counties and damage from early season activity will likely be observed shortly. Dig up wilted plants and inspect roots for onion maggot larvae. Once seeded onions have emerged, count out 25 plants per row and put a marker at each end and record the number of plants every week. These damage plots will be valuable to monitor the amount of damage due to maggot flies or other pests throughout the season.

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***	222	186	100	57	25	126	186	44
Essex*	389	333	198	137	68	236	333	113
Chatham-Kent*	352	299	176	120	59	212	299	98
Norfolk**	327	275	159	105	48	192	275	82
Huron***	281	237	141	92	42	167	237	71
Wellington**	262	223	132	87	43	159	223	69
Simcoe County***	276	235	137	93	51	165	235	75
Durham***	295	250	144	97	44	173	250	77
Peterborough	283	241	134	87	40	165	241	69
Kemptville***	305	262	157	103	44	189	262	79
Sudbury***	196	166	95	56	18	118	166	40
Timiskaming***	192	162	81	42	12	107	162	28
Lambton**	338	288	169	117	60	204	288	95
Thunder Bay	125	101	43	22	7	60	101	15
Middlesex*	325	278	169	116	57	200	278	95
Renfrew	288	248	146	91	35	178	248	70