VCR – Vegetable Crop Report – June 22nd, 2023

Welcome to this weeks installment of the Vegetable Crop Report! Precipitation has not gone up much over the last week, with many counties still well below their respective 10 Year Averages.

Brassica Crops – Early cabbage and broccoli are close to harvest. Diamondback moths and imported cabbageworms are common. No cabbage loopers have been reported yet. Dig up stunted plants and check for maggot damage. Check the growing points and undersides of leaves for aphids (Figure 1). Pull back cabbage leaves and look for thrips as populations are starting to climb. With rain in the forecast, be on the lookout for Alternaria over the next two weeks. In new transplants, continue to monitor for cutworms or heat canker.

**Figure 1**. Cabbage aphid colony starting on the underside of a Brussels sprouts leaf.

Carrots – As the crop continues to establish, now is the time to be thinking about aster leafhoppers and aster yellows. Testing in Michigan is finding low infectivity but leafhoppers are being caught in fields and may be flushing if hay is being cut in the area.
Weeds are also showing up in numbers as the dry stretch has left many fields with inactivated pre-emerge herbicides. If pigweed is your problem see this post on new weed control options such as Ultra Blazer.
According to the degree days carrot weevils should be mostly finished laying eggs so later planted fields or re-seeded fields may not need to be treated for carrot weevil.

Cucurbits – Cucurbit downy mildew has been detected on cucumbers in southern Quebec on June 21, 2023. This is the first report this season in the Great Lakes region, following the detection on cucumbers from New Jersey on June 13. All cucumber and cantaloupe growers should be scouting for downy mildew and immediately start on a preventative fungicide program. Refer to this article for scouting and management advice: https://onvegetables.com/2022/06/14/cucurbit-downy-mildew-get-out-and-scout-2/
Reports of cucurbit downy mildew are tracked on https://cdm.ipmpipe.org/.
Contact Katie Goldenhar (katie.goldenhar@ontario.ca; 519-835-5792) if you suspect cucurbit downy mildew in your field.

Garlic – Most fields are less than a month away from harvest. Avoid irrigating two weeks prior to harvest to make it easier to clean bulb wrappers after harvest. The second flight of leek moth is likely starting soon throughout Southwest Ontario. If applying insecticides, a single insecticide application is most effective when it is applied 7-10 days after the date that corresponds to the peak moth capture. All insecticides registered for leek moth are most effective when they make contact with the larvae.

Onion – The pressure of thrips has continued to be low in direct seeded onions, but higher levels are being observed in transplants. Be mindful that onion fields next to hay or overwintering rye are at a greater risk to thrips once they are cut and include counts from at least one location near the field border when scouting for thrips. Stemphylium leaf blight is likely to be observed over the next couple of weeks (Figure 2). If Penflufen was part of the seed treatment, do not start with a foliar group 7 fungicide. For the first application, a product containing mancozeb (group M3s, such as Manzate Pro-Stick, Dithane Rainshield, and Penncozeb 75 DF Raincoat) may provide protection against Stemphylium if it is being applied to manage onion smut, Botrytis or Alternaria/Purple Blotch. Avoid applying products from the same chemical group one after the other to manage Stemphylium. For the second foliar product, products containing a group 7 show the best efficacy, such as Sercadis, Aprovia, or Miravis Duo (group 7/3). Research has shown that there is very high resistance in Stemphylium to one of the fungicides in Quadris Top (group 11/3) and in Luna Tranquility (group 7/9). Onion and seedcorn maggot have reached their second-generation thresholds. Over the next couple of weeks, monitor for wilt caused by these maggot flies as well as onion smut and white rot.

**Figure 2**. Onion leaf with Stemphylium or Alternaria spores causing black spotting in a tan lesion – June 24, 2020.

Potato – The potatoes appreciated the recent rains and fields are looking very good. Colorado Potato Beetle resistance testing continues this year so if you’re seeing higher levels of beetles and your at-plant insecticide doesn’t seem to be holding up please reach out to have your population sampled for free (dennis.vandyk@ontario.ca or 519-766-5337).

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***	617	548	359	250	130	419	548	208
Essex*	881	790	554	425	255	625	790	366
Chatham-Kent*	812	724	499	375	215	569	724	320
Norfolk**	794	708	490	368	211	557	708	311
Huron***	693	615	417	302	163	478	615	250
Wellington**	695	622	429	316	178	490	622	266
Simcoe County***	691	617	417	308	172	479	617	259
Durham***	751	671	460	345	197	524	671	293
Peterborough	695	619	410	295	154	475	619	245
Kemptville***	747	671	464	341	187	530	671	284
Sudbury***	588	526	357	259	144	411	526	216
Timiskaming***	606	542	362	259	145	420	542	216
Lambton**	760	676	455	336	183	524	676	281
Thunder Bay	504	445	287	205	104	337	445	168
Middlesex*	782	701	490	369	213	555	701	315
Renfrew	754	680	476	355	206	542	680	302