VCR – Vegetable Crop Report – June 10th, 2021

Temperature – Day temperatures are forecasted to range from low 20s to high 30s depending on the region. Nighttime temperatures are forecasted to be around the mid-teens for most regions over the next week.

The recent few days of relatively hot weather in most regions have resulted in a spike in the growing degree days compared to the 10-year average. Most regions are now about 100 growing degree days ahead of their respective 10-year averages except for Peterborough which is about 50 degree days ahead.

Rainfall – Precipitation forecasts vary widely based on region, with most regions forecasted to have showers this Sunday the 13th. So far, June has had a significant increase in the amount of rain compared to May. Regions such as Essex, Chatham-Kent, Norfolk, Huron, Wellington, Kemptville, and Sudbury have already roughly matched or surpassed the amount of rain received in the month of May.

Crop Updates

Asparagus – As some growers begin to finish harvest, scout establishing fern for signs of rust and Stemphylium. Treatments are most effective when applied preventatively before the disease becomes established on the fern. Lesions usually appear on the bottom 12-24” of the stalk. Also scout carefully for asparagus beetle larvae. They often first appear in immature plantings, where they can have a significant impact on the health of the crop.

Brassica Crops – Flea beetles, cutworms and imported cabbage worms are active. Slug feeding damage on lower leaves has been reported. Irregular-sized holes on the inside of the leaves that have smooth edges are often the result of slug damage (Figure 1.), while flea beetle holes are smaller and imported cabbageworm damage is often larger, more ragged and a caterpillar can normally be found feeding throughout the day.

**Figure 1**. Slug damage on broccoli – June 2021

Carrots – Carrot weevils are out and actively laying eggs. If the carrots are in the 2-4 leaf stage or later they may be at risk of carrot weevil damage. There have been some localized catches of carrot rust flies but counts are generally low. Heat canker and stand losses have been common. Keep on irrigating.

Celery – Aster leafhopper, carrot weevil, and tarnished plant bugs (Figure 2.) are active and degree day thresholds have been reached in all regions.

**Figure 2.** Tarnished plant bug on celery – Meagan Stager, June 2021

Cucurbit Downy Mildew – We have installed a network of passive spore traps across the Chatham-Kent, East Elgin and Norfolk growing regions. We will publish the trap results here weekly. Cucurbit downy mildew has not been identified in Ontario or the Great Lakes region, but sporangia have been detected in Michigan. To date, field infections have been identified in Florida, Georgia and South Carolina. For more information about fungicide selection and timing, visit: https://onvegetables.com/2021/06/10/cucurbit-downy-mildew-get-out-and-scout/

Garlic – The number of adult leek moths trapped has been down over the past two weeks and it’s likely that the second flight will be occurring shortly. Target the next wave of leek moth larvae a week after the next peak of adults trapped. Scapes are emerging emerge across Ontario in ‘Music’ and other hard neck cultivars. Be on the lookout for leek moth feeding damage to the scapes (Figure 3.) and kill any larvae or cocoon that you observe while scaping. Cut scapes of hardneck cultivars as soon as possible for 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. The second generation of seedcorn maggot will be emerging soon in many regions, so dig up wilted plants and inspect the roots/bottom of the bulbs for feeding damage.

**Figure 3**. Garlic scape with leek moth larvae feeding damage and a leek moth cocoon – June 10, 2021

Leafy Greens – Leafminer pressure is high and will cause damage that is similar to frost (Figure 4.). Cut a leaf and hold it up and you may be able to see the dark spots of the larvae within the leaf.

**Figure 4**. Leafminer damage in spinach and Swiss chard – June 2021

Onions – Many direct seeded onions have reached the 3rd leaf stage and some areas are even a little further along. The pressure of thrips is low in direct seeded fields, but will increase dramatically as we see more hot and dry weather. 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). 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. Onion maggots, wireworms, millipedes and cutworms are active and the second generation of seedcorn maggot has emerged in some regions and will be emerging shortly in the remaining regions.

Potatoes – Colorado Potato Beetles Wanted, dead or alive. (Figure 5.). We are looking for samples of Colorado Potato Beetles. Around 25-30 adults, even just picked off of some potato volunteers would be enough for a sample. If you have a jar full or are interested in helping out please contact Dennis (519-766-5337, dennis.vandyk@ontario.ca).

**Figure 5.1** Dead Colorado Potato Beetle in potato field – June 2021

**Figure 5.2** Colorado Potato Beetle on potato leaf – June 2021

Insect activity appears to be high this year but one with particularly high numbers is potato leafhoppers. Check your fields for small lime green leafhoppers as seen in the picture. At this point, the at-plant insecticides should be controlling this first generation but keep an eye out for hopperburn symptoms. (Figure 6.).

**Figure 6.** Potato Leaf Hopper on leaf of potato plant

Sweet corn – Based on growing degree days (base 10) European corn borer has reached peak flight for the first generation in Essex. Chatham-Kent is not far behind. Also, be on the lookout for cutworm.

Pest Degree Day Forecasting

*NOTE: Data as of June 9th, 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*	780	698	468	349	221	539	698	301
Chatham-Kent*	726	646	438	327	188	501	646	281
Norfolk**	703	625	417	307	171	482	625	259
Huron***	663	591	407	309	183	462	591	268
Wellington**	602	528	346	250	136	400	528	210
Simcoe County***	640	564	369	270	154	427	564	229
Durham***	616	543	343	253	136	402	543	214
Peterborough	579	504	311	220	115	368	504	183
Kemptville***	698	621	408	296	165	474	621	251
Sudbury***	509	447	296	224	123	340	447	191