Production and pest update brought to you by the OMAFA Apple Team: Erika DeBrouwer, Tree Fruit Specialist and Kristy Grigg-McGuffin, IPM Specialist 

Orchard Activities

Across the province growers are beginning early planting and are in the later stages of pruning. Spring fertilizers are starting to be applied and spray season has begun. Thinning strategies are also top of mind as growth staging progresses.

Growth Stages

Warm and sunny weather over the past few days has pushed apple growth substantially compared to last week’s cool temperatures. Across the province, we are seeing the following growth stages:

• Essex – half-inch green to tight cluster
• Chatham-Kent – half-inch green to early tight cluster
• Lambton, Middlesex, Elgin – half-inch green to early tight cluster
• Norfolk – half-inch green to early tight cluster
• Brant, Wellington – green tip to half inch green
• Niagara – half inch green to early tight cluster
• Grey – green tip
• Durham, Northumberland and Quinte – green tip to half inch green
• Ottawa Valley – green tip

Scab: Are We There Yet?

With the flush of growth and warm days over the last week to encourage ascospore maturity, this rain event much of the province is currently experiencing may be the start of the first apple scab infection period of the year.

If you’re looking for more information on how temperature and leaf wetness affect scab infection, check out the table Relationship of Temperature and Moisture to Apple Scab Infection.

Covered in Rainy Stretches

Apply protectant fungicides (e.g., mancozeb, captan, folpet) now if not already covered. Most of the available mature spores are discharged within 2 hours after the start of a wetting event. If using protectant fungicides alone, remember these are contact fungicides and do not provide effective post-infection or anti-sporulant activity.

If heavy rains greater than 2″ occur, residues will have likely been washed off. Reapply at any break in the rain if things continue over a period of days. Be prepared to cover again once things dry up.

If there are any concerns about residue wash-off, you may want to consider going in after the rains have stopped with a post-infection, or kickback product. Refer to Characteristics of Apple Scab Fungicides for more information.

• Cooler weather products that may offer some kickback protection include Syllit (do not use beyond tight cluster), Scala, Inspire Super, Luna Tranquility and Buran.
• Other products belonging to Groups 3, 7 or 11 can also be used, especially if things are further along in development and more broad-spectrum disease control is needed, such as for powdery mildew or rust.
• Where possible, tank-mix systemic fungicides with a protectant such as a Group M (mancozeb, captan, folpet) or a biological product.
• Fluazinam (Allegro, Vantara) does not offer post-infection activity; this is a contact product.

What About Mildew?

While it might seem a little pointless mentioning powdery mildew in the midst of rain (hint: rain deters powdery mildew development), things will eventually dry up. High powdery mildew pressure in recent years followed by the mild winter could be an unwelcome mix resulting in an early spring arrival of this disease.

Be sure to consider a mildew protectant such as a low rate (3-5 kg/ha) of sulfur in your early season scab program, especially on susceptible cultivars or orchards with a history of powdery mildew. Continue this until tight cluster when more systemic fungicides with mildew activity like the Group 3, 7 and 11s start to be used. Watch your use of sulphur around oil sprays – read the product label for more information.

As mentioned, rain washes off powdery mildew spores. Instead, mildew is spread by wind and thrives in dry weather and high relative humidity. So, protectant sprays may still be required during dry periods when there is little risk from apple scab.

Save the Date! Apple IPM Workshop

Looking for a chance to refresh your knowledge of apple IPM? New to growing or scouting apples?

Join me for an Apple IPM Workshop!

• VIRTUAL – Friday, May 2nd from 9:00AM – 12:00PM
• IN-PERSON (Simcoe) – Monday, May 5th from 9:30AM – 3:30PM

We will discuss common orchard pests, scouting techniques for various insects and disease, tools of the trade, safety protocols and tips for success. Time will also be available to answer any pest-specific questions regarding pre-recorded presentations available on the ONhortcrops YouTube channel.

Other IPM workshops are also being offered over the coming weeks. Click below for more information.

Register Now! FREE IPM Training Workshops