Why more precision is required to protect apple crops

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The system algorithms are based on simulation models that are developed, tested and regularly updated by scientists in apple and grape-producing regions around the world. Spaying recommendations are updated every 30 minutes, based on local weather data. Using five systemcompatible weather stations strategically located throughout the farm, Boonzaier will have the ability to micro-manage spray applications based on the localized need.

Manitree Fruit Farms, another Ontario apple grower near Blenheim, Ontario, is also experiencing protection complexities multiplying with the loss of some uses of group M fungicides and others.

“I saw the writing on the wall in 2017 when I attended a minor use priority setting meeting in Ottawa,” recalls Brian Rideout, farm manager. “The trend in product registrations was moving away from broad-spectrum fungicides to single-site fungicides. And the alternatives were clearly in biologicals.”

This was a wake-up call for directing forward-looking crop protection strategies for his 400 acres of tree fruits – peaches, pears, tart cherries, apples – as well as vegetables. Located on the north shore of Lake Erie, he’s in a micro-climate that favours a multitude of crops. Fortunately, given his role as chair of the crop protection section of the Ontario Fruit & Vegetable Growers’ Association (OFVGA), Rideout is a guy who questions the status quo and teases out the strands of complex problems.

In the last two years, PMRA has stipulated that many fungicide products must be used more sparingly in quantity, less frequently in timing and with more limits for the pre-harvest interval and re-entry interval. Mancozeb, for example, is now labelled for a 77-day pre-harvest interval and a 35-day re-entry interval for hand thinning.

Backtracking from harvest date it’s easy to see that application windows have become narrower.

“In the past, group M fungicides formed the backbone of our crop protection programs,” explains Rideout. “If you think of a pyramid, they have been the base because you could use them more than once and on more than one crop.”

Decreasing reliance on these products has a cascading effect on farm decisions, from warehouse inventory to the cost of more biological products and management of orchard workers. The bottom line ends up taking a double hit through an increase of about 10 per cent in upfront costs and through a higher risk of disease outbreaks.

Activity of Fungicide s on Apple Diseases

Apple Disease Efficacy Table

Use fungicides only for the disease listed on the product label for the crop. The information provided in this table is inten ded to assist the grower in choosing the best fungicide for control of pests listed on the product label, while managing resistance and avoiding unnecessary sprays for non -target pests. Efficacy can be affected by rate of the product or by the presence of resistant populations.

Apple Disease Efficacy Table available on the Ontario Crop Protection Hub. https://cropprotectionhub.omafra.gov.on.ca/

As Rideout has determined through several years of on-farm trials, biologicals and chemistries together have their strengths. But removing the umbrella control offered by group M fungicides invites the return of heretofore little-seen diseases such as sooty blotch, flyspeck and frog-eye leaf spot. Clearly, no grower wants to apply expensive crop protection products from early spring to August only to find cosmetic blemishes on apple crops come harvest.

Given a reduced application window of group M fungicides occurring earlier in the season, apple growers need to develop new protection strategies for the rest of the summer. Like many other growers, Rideout uses Buran, a liquid formulation containing garlic extract to protect his harvest. It may not be the perfect bullet, but it helps.

For extension workers such as Katie Goldenhar, plant pathologist, OMAFRA, the relatively inexpensive group M fungicides have been a critical component of resistance management for single-site fungicides. She agrees with Rideout that there’s an outstanding question. “How and when do we use the tools that are left to manage apple scab and summer diseases?”

“In my opinion,” she continues “the reduction of uses and cancellations of group M products are leading the horticulture industry towards increased disease management costs: increased disease outbreaks, increased resistance to single-site fungicides and increased emergency use registrations.”

For Boonzaier, Rideout and many other growers, micro-management of each orchard block is fast becoming the new orderseven days a week, all season long.

The Grower is “Digging Deeper” with Brian Rideout, Manitree Fruit Farms, Blenheim, Ontario. He talks about the complexities of managing apple orchards with more limited access to group M fungicides. This podcast is sponsored by Cohort Wholesale.