VCR – Vegetable Crop Report – June 12th, 2025

Welcome back to the next VCR of 2025!

Currently most counties are trending close to their 10 year average GDD, with some trending slightly above or below.

Crop Updates

Brassica – Imported cabbageworm, cabbage looper, and diamondback moths are active, and slug, flea beetle, as well as cutworm damage has been observed. To determine if the threshold for management has been met for imported cabbageworm, diamondback moth or cabbage looper (Figure 1), scout 5 plants in 5 locations and record the total number of each lepidopteran pest found (total number of egg or larvae found):

Multiply:

Diamondback moth x 0.2 = A

Imported cabbageworm x 0.5 = B

Cabbage looper x 1.0 = C

Then add and divide:

A+B+C divided by 25 = Cabbage Looper Equivalent

For cabbage, the threshold is 0.3 and for broccoli and cauliflower the threshold is 0.2.

	Diamondback Moth	Imported Cabbageworm	Cabbage Looper
Eggs	-Scale-like eggs laid in small groups	-Yellow, bullet-shaped with ridges	-round, greenish-white
Larvae	-hairless	-Green larvae, short hairs, velvet-like appearance	-inchworms with thin white line along each side
Damage	-Create windows in leaves, do not consume through leaf	-Ragged holes and dark green frass not in piles	-Ragged holes and dark green frass in piles
Relative Damage (Cabbage Looper Equivalent)	0.2	0.5	1.0

Figure 1 – Diamondback Moth, Imported Cabbageworm, Cabbage Looper eggs, larvae and adult moths and butterfly. Figure originally published in Publication 839.

Celery – Transplants are establishing. The thresholds for aster leafhopper and tarnished plant bug have been reached across the province with the exception of Thunder Bay. Dig up wilted plants and inspect the roots/plug for cutworm larvae. Scout for carrot weevils as they may be emerging around the field borders.

Cucurbits – scout all fields for cucumber beetle activity, especially where transplants were used or where there was a delay in germination. Seed treatments with thiamethoxam usually provide up to 3-weeks of control. Were beetles are active, use a foliar insecticide before the plants begin to flower. Beetle control is needed to prevent the spread of bacterial wilt disease.

A free Ontario focused mobile app called SCOUT IPPM, developed at the University of Guelph is available for pumpkin and squash growers. Scout IPPM allows growers to monitor the striped cucumber beetle and pollinator populations simultaneously. The app is available for all mobile devices here

Sandea herbicide can be used as a post emergence weed control in cucumbers, pumpkins, squash and watermelon. It should be applied over the rows no later than the 3-5 leaf stage or 14 days after transplanting and before the appearance of first female flower. Row middles can be sprayed at all crop stages. Do NOT spray over top of plastic mulch. Do NOT apply more than 140 g/ha (56 g/acre) per season.

Garlic – Plants are starting to bulk up with bulbs differentiating into cloves. Scapes are starting to emerge. Snap scapes of hardneck cultivars as soon as possible to obtain the greatest yield benefit. Avoid using sickle bar mowers to remove scapes as they can easily spread garlic pathogens (including viruses) and often clip leaves during the scape removal process. Past research has shown that by accidentally removing one leaf when the scape was removed, bulb sizes were reduced by 13% and the yield was reduced by an average of 17.5%. The same trial showed that yield was greatly impacted as the number of leaves cut during mowing increased. If the top two leaves were cut, the yield was reduced by approximately 25%, almost outweighing any potential gains you would expect by removing the scape in the first place. While scaping, be on the lookout for leek moth as well as symptoms of stem and bulb nematode, botrytis neck rot, fusarium basal rot and white rot. If leek moth counts were high last week, consider targeting the larvae that are now feeding on the crop.

Figure 2. Differences in foliar, bulb and root symptoms of some garlic pathogens.

Figure 3. Botrytis neck rot produces greyish-brown mould / mycelium is found on the outside necks of plants above the crown. Black sclerotia are also seen below the mycelium on the stem.

Onions – Onions are starting to take off with the increase in heat over the past week. Onion maggots continue to be active and some fields are showing a fair bit of cutworm damage (Figure 5). Dig a few inches around plants that appear to have been cut with scissors and try to find the cutworm larvae around plants that have been cut. Insecticides targeting cutworms are more effective if the larvae are small and the damage is found early. A list of products registered to manage cutworms in onions can be found on the Ontario Crop Protection Hub. In some areas of the province, conditions have been conducive for sporulation and infection of onion downy mildew (Figure 6). If downy mildew was present nearby last year, it may be worth protecting transplants from infection if the weather continues to be cooler than normal with extended periods of leaf wetness. With this weather, be on the lookout for botrytis leaf blight as well as white rot.

Figure 5. Cutworms continue to cause damage in onions – June 11, 2025.

Figure 6. Onion downy mildew has been found in a community garden in Guelph as of June 6, 2025.

Sweet corn – there have been reports of wireworm damage in fields that were slow to emerge. Symptoms include poor emergence, variable growth and die back. Dig up the area around the plants to look for the larvae. Unfortunately, there are no controls for wireworm after planting. Assess the stand for the population and consider replanting if necessary.

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***	506	438	261	172	78	314	438	137
Chatham-Kent*	700	617	397	282	148	463	617	231
Durham***	594	523	338	231	117	396	523	187
Essex*	764	680	453	326	173	524	680	271
Huron***	581	506	318	221	117	374	506	183
Kemptville***	619	549	361	256	146	420	549	215
Lambton**	660	579	367	257	136	433	579	212
Middlesex**	681	603	392	275	146	457	603	226
Norfolk**	639	560	348	236	120	413	560	190
Peterborough	560	489	301	203	97	358	489	163
Renfrew	597	530	347	248	143	404	530	208
Simcoe***	553	482	302	205	106	357	482	167
Sudbury***	419	367	229	161	86	270	367	134
Thunder Bay	333	286	168	105	35	202	286	78
Timiskaming***	396	346	222	158	81	258	346	129
Wellington Centre**	542	471	288	191	92	345	471	153
Wellington North**	547	478	292	204	104	349	478	168