VCR – Vegetable Crop Report – June 24th, 2021

Temperature – Day time temperatures are forecasted to range from mid to high twenties in most regions.

Nighttime temperatures are forecasted to range from high teens to low twenties for most regions. The Growing Degree Day models for most regions continue to have a similar growth rate as their respective 10-year averages but are still ahead of the average by roughly 100 degree days.

Rainfall – Most regions are forecasted to have rain over the weekend and into next week. June continues to be a great month for precipitation with many regions being relatively close to their 10-year averages. However, Essex is the only region that has surpassed its 10-year precipitation average for the month of June.

Crop Updates

Asparagus – Most asparagus is completing harvest. Scouting for insects and diseases during fern establishment is very important.

Brassica Crops – Early cabbage and broccoli are close to harvest. Lepidopteran pests such as diamondback moth and imported cabbage worm continue to be high in pressure. Flea beetle pressure has decreased in most areas while the pressure of thrips may increase as hay is cut. Now that some areas have had a significant amount of moisture, be on the lookout for Alternaria and downy mildew. Dig up wilted plants with a trowel or shovel and inspect the roots. Wilting can be caused by several pest/pathogens including cabbage maggot, nematodes, clubroot, or wireworm damage. In new transplants continue to monitor for cutworms or heat canker.

Carrot – Early planted carrots are sizing up nicely. Carrot weevils should be wrapping up egg-laying in most areas of the province now, if you have some later planted carrots they may avoid most of the pressure.

Celery – Carrot weevils are active. On celery, carrot weevils leave scratch marks along the stalk that turn a yellow/orange colour as the wounds heal. Continue to scout for tarnished plant bugs and aster leafhoppers. Scout for Aster yellows and celery leaf curl (Figure 1.) and rogue out infected plants. Plants showing symptoms this early in the season will be a source of inoculum for infections later in the season.

**Figure 1.** Celery leaf curl causing downward cupping of leaves on establishing transplants in 2017.

Cucurbits – Since the identification of downy mildew in cucumbers in Kent county last week, there have been no further fields identified with the disease. Angular leaf spot has been found in zucchini and pumpkin. ALS is a bacterial disease and fungicides will not impact its spread. Fortunately plants usually seem to outgrow the damage. Keep an eye out for cucumber beetles. The threshold is 0.5 to 1 beetle per plant.

Garlic – Scaping is wrapping up and many fields are showing leaf tips starting to senesce. Tip dieback (where yellowing/senesce starts at the tip and moves towards the heart of the plant) is likely due to stress which could be from lack of soil moisture, lack of or surplus of nutrients or root dieback. Quick leaf yellowing (where the whole leaf turns yellow) from the bottom leaves moving upwards can result from Fusarium basal rot, bulb and stem nematode (Figure 2.), or other damage to the roots. Leaf yellowing from the top, newest leaves and progressing downward is often caused by Aster Yellows, nitrogen deficiency, Fusarium yellows or herbicide damage. The amount of leek moth captures has increased in several regions. A single insecticide application is most effective when it is applied 10 days after the date that corresponds to the peak moth capture. If you plan on two applications, make the first application 3 to 7 days after the date of peak moth capture and the second treatment 14 days later. Products such as Matador, Delegate, Entrust, Success, Dipel, XenTari and Bioprotec are most effective when they make contact with the larvae.

**Figure 2.** Various degrees of bulb and stem nematode damage on garlic. Look for stunted plants with leaf yellowing from the bottom leaves of the plant moving upward.

Onions – Be on the lookout for onion downy mildew as some areas may have received conducive weather for sporulation and infection. Stemphylium leaf blight is likely to develop over the next couple of weeks (Figure 3). 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 M3) may provide protection. Mancozeb products such as Manzate Pro-Stick, Dithane Rainshield, and Penncozeb 75 DF Raincoat are registered for Botrytis and Manzate Pro-Stick is registered for Botrytis and Alternaria/Purple Blotch. Avoid applying products from the same chemical group one after the other. For the second foliar product, products containing group 7 show the best efficacy, such as Secadis, 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). Follow a group 7 fungicide with T-77 or Bravo. While scouting, dig up wilted plants and look for maggots (Figure 4.), wireworms or pink root. The pressure of thrips is building. Past research has shown that Movento 240 SC (group 23) has some residual activity that works better against larvae when it is applied earlier in the season. If the spray threshold exceeds 3 thrips/leaf, Movento 240 SC could be followed by two applications of Delegate (group 5) or Agri-Mek (group 6). Malathion 85E (group 1B), Dibrom (group 1B), Entrust (group 5), Success (group 5), and Exirel (group 28) are also registered. Using a penetrating surfactant can be useful to maximize the effectiveness of products against thrips. Apply no more than two consecutive insecticides from the same IRAC crop as thrips have a relatively short life cycle with multiple generations through the summer months and are at a high risk of developing insecticide resistance. Botrytis leaf blight and onion smut has been observed in some regions.

**Figure 3.** Onion leaf with Stemphylium or Alternaria spores causing black spotting in tan lesion – June 24, 2020.

**Figure 4.** Onion maggot larvae. Alexandra Switzer, June 23, 2021.

Potatoes – Colorado Potato Beetle larvae are hatching and feeding in most areas of the province (Figure 5.). Time sprays to hit early instars if you are going to use a foliar application. Don’t use a Group 4 insecticide (Clutch, Assail, Actara, Admire) foliar spray if you applied Cruiser, Actara, Titan or Admire at seeding. Symptoms of blackleg (Figure 6.) are evident right now as the plants will be wilted and dying. Seeing lots of tarnished plant bugs this year (Figure 7. and 8.). Be mindful of flushes of leafhoppers entering potato fields as there are lots of first cuts going on right now.

Figure 5. Colorado Potato Beetles as eggs, feeding instars, and molting larval instars

**Figure 6.** Blackleg damage on potato plants

**Figure 7.** Tarnished Plant bug on potato leaf – June, 2021

**Figure 8.** Tarnished plant bug feeding damage – June, 2021

Pest Degree Day Forecasting

*NOTE: Data as of June 23rd, 2021

Pest	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
Essex*	1032	936	664	517	347	749	936	455
Chatham-Kent*	948	854	603	465	277	680	854	404
Norfolk**	899	809	566	431	254	642	809	371
Huron***	855	770	544	418	246	612	770	363
Wellington**	795	708	483	359	199	552	708	305
Simcoe County***	843	753	516	389	226	588	753	334
Durham***	826	738	497	378	214	569	738	326
Peterborough	773	683	449	330	178	519	683	278
Kemptville***	899	809	554	413	236	634	809	355
Sudbury***	662	588	401	306	168	457	588	262