VCR – Vegetable Crop Report – June 15th, 2023

Welcome back to the VCR! This week, many counties experienced rain, bringing their precipitation totals higher, although no county has made it past the ten year average yet.

Brassica Crops – Cutworms have been found in multiple fields across the province. Damage found on the lower leaves of plants with no sign of lepidopteran pests may be the result of early-morning slug feeding. The degree day threshold has been met in most areas in Southern Ontario and if wilted plants are found, dig up the transplant and inspect the roots for cabbage maggot larvae to confirm. With imported cabbageworm and diamondback moth larvae active, thresholds for management can be used to determine if action should be taken. Scout 5 plants in 5 locations and record the total number of each of the lepidopteran pests:

Multiply:

Diamondback moth x 0.2 = A

Imported cabbageworm x 0.5 = B

Cabbage looper x 1.0 = C

A+B+C and divide 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

Garlic – Scaping is underway across the province. If scapes are to be consumed, ensure that any herbicide PHIs have been met. When scaping, avoid using sickle bars mowers to cut the scapes, as they often cut leaves that will reduce the yield potential, as well as spread pathogens between plants. Better yields have resulted when the scape is snapped an inch above the youngest leaf. Pulling scapes instead of snapping can cause the upper leaves to lose support and fall over causing pre-mature senesce. Avoid applying any nitrogen past the 5th leaf stage as this has been found to cause ‘rough’ bulbs with cloves forming outside the main bulb wrapper.

Onions – The largest direct seeded onions are reaching the 5th leaf stage in many areas and transplants are really starting to take off. Cutworm damage is sporadic in some fields. Damage due to onion maggot, wireworms and millipedes is being observed. Low levels of thrips are starting to be observed. Past research has shown that Movento 240 SC (group 23) has some residual activity that works better against larvae when it is applied twice earlier in the season. Once the spray threshold has been met, 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.

**Figure 1.** Count the number of onion thrips on 10 plants and divide this total by the average number of leaves.

Peppers – Pepper planting is still ongoing, as Growers got a bit of a late start due to the frost events in May. Also, the recent rain is a big relief for many growers who have not put down irrigation lines. Growers in 2-generation and overlap European corn borer areas should be on the look-out for the pest as the first peak is approaching in Essex and Kent counties and has begun in the London and Sarnia areas. Though the second peak will be more worrisome as the plants will have fruit at that time, there are many control options available for growers in need. Always make sure to read all product labels before any pest control product application.

Tomatoes – Planting is wrapped up for processing tomatoes. Early plantings that survived the frost events in May are approaching first bloom. One issue that is popping up this year is Colorado potato beetle (CPB). Since losing key in-furrow insecticide products two years ago, this is the first time growers are seeing significant damage from the pest in many years. CPB is critical to manage during the transplant phase as the adults and larva (Figure 2) can cause significant defoliation of plants, often leading to plant death. There are a few foliar products that growers can use for CPB control, but you will need multiple applications to control these early populations. Target adults when you start seeing damage, then follow-up with another spray using a product from a different insecticide group 5-7 days later once eggs have begun to hatch (Figure 3). Continue to monitor for CPB and damage as additional applications may be needed. Be sure to read all product labels thoroughly before any pest control product application and follow resistance management strategies. CPB are known to be resistant to group 1 insecticides in Ontario many parts of Ontario.

**Figure 2**. Colorado potato beetle adult and eggs on tomato transplant

**Figure 3.** Colorado Potato beetle larva freshly hatched from eggs on defoliated tomato transplant.

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***	509	448	283	190	94	335	448	155
Essex*	754	672	459	346	200	523	672	296
Chatham-Kent*	694	615	414	305	170	476	615	258
Norfolk**	670	592	398	291	159	457	592	243
Huron***	585	515	341	242	126	393	515	198
Wellington**	582	518	350	253	138	403	518	210
Simcoe County***	584	517	341	248	136	395	517	207
Durham***	629	557	370	271	147	425	557	226
Peterborough	583	516	331	231	114	387	516	189
Kemptville***	627	559	376	269	139	434	559	220
Sudbury***	509	452	302	216	118	350	452	178
Timiskaming***	496	440	285	198	108	335	440	163
Lambton**	654	579	382	279	150	443	579	232
Thunder Bay	403	352	219	153	76	261	352	124
Middlesex*	681	607	417	310	174	474	607	263
Renfrew	630	564	384	280	154	442	564	235