VCR – Vegetable Crop Report – June 6th, 2024

This first week of June, many Southern and Western counties such as Chatham-Kent, Huron, Middlesex, and Norfolk have experienced more rain than their 10-year average trend for the first week of June. Some Eastern counties such as Renfrew and Kemptville have received less rain than their 10-year average trend.

All counties continue to trend above their 10 year average GDD.

Crop Updates

Brassica Crops – Dig up wilted plants to inspect the roots for cabbage maggot larvae as larvae are likely to be actively feeding. Cimegra (active ingredient broflanilide, IRAC group 30) has been temporarily registered as an emergency use for cabbage maggot management for broccoli, Brussels sprouts, cabbage, and cauliflower for use in 2024. Broflanilide is a new active ingredient that can be applied as a post-planting drench banded spray. For best results, apply at peak egg laying activity based on sticky card counts or growing degree days for your region. Otherwise, Success (Group 5) and Verimark (Group 28) are registered as greenhouse tray drenches and Verimark can also be used as an in-furrow application in the transplant water at the time of transplanting. Imported cabbageworm, cabbage looper, and diamondback moths are active and slug, flea beetle, and 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.

Celery – Transplants are establishing. The thresholds for aster leafhopper and tarnished plant bug has 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.

Garlic – The second flight of leek moth has started and with eggs hatching, be on the lookout for damage as hardneck cultivars are scaped over the next two weeks. Refer to this article for managing leek moth: Monitoring for Leek Moth. 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.

Onions – Some direct seeded fields are at the 4^th leaf stage however most fields are averaging around the 2^nd leaf stage. Onion maggot damage has been observed. Stake out 100 plants now to help determine how many onions make it to harvest. The pressure of thrips is low in direct seeded fields. 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. Once the spray threshold is reached, 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 group 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.

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***	555	482	303	205	98	357	482	165
Essex*	834	750	526	402	238	596	750	345
Chatham-Kent*	752	673	463	350	195	528	673	294
Norfolk**	702	621	405	292	152	471	621	240
Huron***	630	554	353	245	129	415	554	199
Wellington Centre**	608	531	342	240	120	398	531	195
Wellington North**	595	521	334	236	122	392	521	192
Simcoe***	590	517	330	227	112	386	517	180
Durham***	641	563	365	258	132	426	563	211
Peterborough	586	510	322	219	104	380	510	175
Kemptville***	641	565	382	282	159	436	565	237
Sudbury***	461	402	256	177	89	301	402	142
Timiskaming***	443	390	254	179	96	295	390	147
Lambton**	726	649	440	325	185	505	649	273
Thunder Bay	331	276	146	86	25	182	276	61
Middlesex**	741	660	446	330	186	513	660	278
Renfrew	627	554	372	277	157	427	554	234