Disease Insects Pest Management Vegetables Weather

VCR – Vegetable Crop Report – July 30th, 2020

The VCR (vegetable crop report) is a weekly update which includes crop updates, weather and growing degree summaries for various vegetable growing regions across Ontario. Continue Reading VCR – Vegetable Crop Report – July 30th, 2020

Ontario DD Map_jul30 Temperature – Temperatures are expected to remain below 30C this upcoming week and may even drop to the low 20s in many regions.  All regions have surpassed their GDD 10 year average. Carrot rust fly is at its second threshold in Essex, Chatham-Kent, Norfolk, and Durham regions, and Kemptville. Onion maggot has reached threshold in all regions except Essex which has now passed the second threshold range. Cabbage maggot and Seedcorn maggot are at threshold in Sudbury. Degree day data for each region is shown below.

Rainfall – Many regions received precipitation levels near their 10 year averages in July but still lag marginally behind. Exceptions include Durham and Peterborough regions, which received around half their 10 year precipitation averages, and Sudbury, which received more than double the 10 year average. There is a chance of thunderstorms starting Sunday and chances of rain continuing into the week throughout Ontario.  Precipitation data for each region is shown below.

Crop Updates

Brassica Crops – Lepidopteran pests continue to be an issue across the province. For information on scouting thresholds, see the VCR post from June 18. High temperatures from 3-4 weeks ago has been hypothesized to be the reason there is uneven growth in broccoli or cauliflower heads that are currently being harvested. Alternaria is starting to show up in some fields. As blocks are harvested, incorporate residue to lower the overall spore load. Often bacterial rots enter broccoli or cauliflower heads where an insect has chewed or where fungi have damaged the cell wall. With uneven heads and trapped water droplets, it’s likely that there will be bacterial rot observed over the next few weeks. Given the high humidity and colder mornings, be on the lookout for downy mildew.

Carrots – Leaf blights continue to show up in some fields. Alternaria leaf blight will look like the leaves are burnt. Cercospora leaf blight will be spotty with elliptical lesions on the stems. Not all fungicides will work on both blights. Use a 25% incidence spray threshold. Some areas of the province are at risk for the second generation carrot rust fly. It’s easy to monitor for carrot rust fly with yellow or orange sticky cards around the edge of the field.

Celery – Bacterial rot is taking down infected plants in some fields and celery leaf curl has been observed in several fields. Tarnished plant bugs are active.

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Figure 4. Bacterial rot of celery, July 28th, 2020.

Cucurbits – Harvanta (cyclaniliprole) is now labelled for cucumber beetle suppression. Refer to last week’s VCR for usage details – cucumber beetles remain active. We are continuing to track this year’s downy mildew epidemic, if you are observing symptoms of downy mildew on any crops including melons (including watermelon), pumpkin, and squash we would be interested in hearing from you.

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Figure 5. Downy Mildew, Simcoe, Norfolk county July 24 (Top) and July 28th (Bottom) Top: Downy mildew lesions and sporangia on a cucumber leaf, Bottom: Downy mildew can cause defoliation, breaks in the canopy can lead to sunscald on fruit decreasing marketability.

Squash bugs are increasing, but do not usually cause problems in commercial fields as they are susceptible to several insecticides. When scouting, take note of egg masses like the ones in Figure 6, the threshold is one egg mass per plant.

squashbugeggs_jul30
Figure 6. Squash bug egg masses are yellow when laid, and turn reddish brown as they mature. Usually found on the underside of leaf, although sometimes on the topside as depicted.

Continue to scout for Phytophthora in cucurbits and other crops: Examine low lying or poorly drained areas noting any wilted or stunted plants, and look for lesions. Phytophthora usually presents as a foliar blight or a crown rot in zucchini, squash, and pumpkin, so look for dark lesions on the crown. In cucumbers and melons Phytophthora usually causes fruit and stem lesions so look for water soaked lesions with white spores developing on the fruit. Maintain good biosecurity practices, and please contact Andrew Wylie (andrew.c.wylie@ontario.ca) or Katie Goldenhar – Pathologist-Horticulture (katie.goldenhar@ontario.ca) if you observe symptoms resembling Phytophthora.

Garlic – Thinking of planting a new cultivar? Take a look at last year’s garlic cultivar trial that summarizes 22 cultivars grown at three field sites – Click here to visit the 2019 Garlic Cultivar Trial post. Be sure to test all planting stock for bulb and stem nematode before planting in your field. Low levels of nematodes can be found in planting stock that otherwise looks great.

Onions – Be on the lookout for downy mildew given the high humidity, heavy dews and colder mornings. The 2017 Muck Crops Research Station Greenbook report summarizes downy mildew product efficacy on page 66: Click here to visit page 66 of the 2017 Greenbook. Stemphylium, purple blotch, botrytis, onion smut, pink root have been observed.

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Figure 7. Botrytis leaf blight, July 28th, 2020.

Potatoes – Second generation of CPB seem to be emerging in some fields. If numbers are above threshold don’t use a foliar neonic (Assail, Alias, Admire, Actara, Clutch) if you used a neonic at planting (Actara, Titan, Cruiser Maxx). No reports of late blight in the region but protectant sprays are still important. Starting to see some early blight show up on older leaves. Localized outbreaks of leafhoppers have been seen in some fields. Keep an eye out for European corn borer in some regions of the province (check table below for your region).

hornwormpot_jul30
Figure 8. tobacco hornworm feeding on a potato plant.

Sweet corn – Sweet corn harvest is underway and lepidopterans are numerous. Click here to listen to last week’s  interesting podcast on caterpillars in sweet corn from the Great Lakes Vegetable Producer’s Network (also available on Spotify and Apple Podcasts) and check out the Great Lakes and Maritime Pest Monitoring Network for up-to-date reports of pest levels.

NOTE: Data as of July 29th, 2020

Pest Degree Day Forecasting

PestCarrot Rust FlyOnion MaggotCarrot WeevilAster LeafhopperTarnished Plant BugCabbage MaggotSeedcorn MaggotEuropean Corn Borer
THRESHOLD329-395, 1399-1711210-700, 1025-1515138-156, 455+128+40+314-398, 847-960, 1446-1604200-350, 600-750, 1000-1150See legend below
Essex*168115511207101675813151551927
Chatham-Kent*15381414109591363211931414828
Norfolk**15361412108290162211831412815
Huron***1326121993375949810231219676
Wellington**1331121892875950610181218679
Simcoe County***1352124195578653410461241706
Durham***14541339103686359911281339781
Peterborough130911948987274709891194645
Kemptville***14321320102085059211101320770
Sudbury***121011178647144769431117641

 

*- Bivoltine region for ECB. First Peak Catch: 300-350 DD, Second Peak Catch 1050-1100 DD

**- Overlap region for ECB. First Peak Catch : 300-350 DD Second Peak Catch 650-700 DD, Third Peak Catch 1050-1100 DD

***-Univoltine region for ECB. Peak Catch 650-700 DD

Use these thresholds as a guide, always confirm insect activity with actual field scouting and trap counts.

Select a region below for the latest weather, crop and pest degree day information:

Essex County

Chatham-Kent County

Norfolk County

Huron County

Wellington County

Simcoe County

Durham County

Peterborough

Kemptville

Sudbury

Essex County

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Chatham-Kent County

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Norfolk County

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Huron County

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Wellington County

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Simcoe County

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Durham County

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Peterborough

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Kemptville

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Sudbury

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4 comments on “VCR – Vegetable Crop Report – July 30th, 2020

  1. The output of the sun, sunlight is assumed to be a constant. But the sun is not constant. While there are no big swings in any years, there are fluctuations over 10 to 20 year periods and NASA is measuring that. Would it be possible to include this data with your charts? Also, what the plants see in terms of sunlight will depend on cloud cover/humidity in the air. So, humidity is another factor since plants my uptake up to ~50% of their H20 requirements via foliage.This suggest we should also be looking at daily integrated solar irradiation, and also humidity for each of the counties.

    • Travis Cranmer

      I agree that it would be interesting to include solar irradiation and humidity, but we do not have the sensors to provide this data at this time.

  2. Francine Colbourne

    Where do I find information for Prescott-Russell?

    • Dennis Van Dyk

      Hey Francine, we are currently using Environment Canada weather stations with consistent long-term data which sometimes limits the available sites. Currently the closest we have would be Kemptville. We are in the process of expanding the number of stations and counties available so stay tuned.

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