Scab-Immune Apple Varieties Are Worth a Try

Feb 02, 2022

By David Lowenstein

Photo 1. Apple scab on leaves. Photo from MSU Extension.

Apples are one of the most popular fruits consumed by people of all ages. They come in a wide variety of colors, sizes, tastes and are used in many products as a primary and secondary ingredient. What makes them even more desirable is that apple trees are cold hardy and relatively easy to grow in your backyard. Unfortunately, apple trees are also susceptible to a variety of diseases including apple scab.

What is apple scab?

Apple scab is a fungus, Venturia inaequalis, affecting most apple varieties. In spring, the fungus spreads from overwintered spores of infected leaves to new leaves through wind and splashing from rain. The risk of scab is greater in years with wet springs. As the spores reproduce within the plant, circular brown to black lesions develop several weeks later on the leaves (Photo 1). Areas around the lesions will sometimes lighten in color or turn yellow. The size of lesions can range from very small to large enough to cause early leaf drop and unmarketable fruit. In more severe cases, the tree may drop its leaves in July or August.

In addition to lesions on the leaves, scab-infected trees will produce brown and corky apple fruits (Photo 2).

scab_immune_apple_varieties_can_reduce_pesticide_use_for_the_backyard — Photo 2. Raised blotches on apples that indicate scab infection. Photo by Bill Shane, MSU Extension.

Preventing scab with fungicides

Trees that have apple scab can continue to produce new leaves in the following season. Michigan residents with crabapple trees can do nothing, as the damage will only be cosmetic. Fall removal of scab-infected leaves from the orchard floor is essential to reduce the risk of scab transmission in future seasons.

Applying fungicides to the leaves is one preventative treatment. To achieve a good yield of fruits without scab, fungicide applications every 10-14 days are required from when a half inch of the green tissue has grown (green tip) through the week after petal fall. Captan and Myclobutanil are two fungicides that home orchardists can apply. If your tree already has apple scab, it is too late to apply a fungicide that will eradicate the disease.

Michigan State University Extension always advises that gardeners who choose to use chemicals must read the product label before application and to confirm that it is registered for use in the location they plan to spray.

Preventing scab with resistant varieties

In recent years, an increasing number of scab-immune apples have been developed by plant breeders from across the United States and elsewhere. Some selections have resulted from cross breeding and others from natural mutations in the field. These resistant options are great news for backyard orchardists. Fewer sprays will result in a cost savings and protecting the environment; a win-win situation. In addition, partial or total resistance to diseases fits well into organic management practices for organic growers.

Several commonly grown varieties such as Cortland, McIntosh and Honeygold have a high susceptibility to scab. A list of apple varieties and their susceptibility to scab is available on a Michigan State University Extension resource on scab susceptibility by variety. Another excellent resource is “Apple scab of apples and crabapples” from the University of Minnesota Extension.

Some popular, scab-immune apple varieties for the Michigan home orchardist to consider include:

Pristine: A very early, large green or yellow apple (pies or sauce).
Redfree: An early, medium-sized, red apple (fresh, pies or sauce).
Macfree: Early season, McIntosh-type of apple (fresh or sauce).
Freedom: Large fruit that is also resistant to cedar apple rust and fire blight. Can bruise easily (cooking and pies).
Jonafree: Similar to Jonathan with pale-yellow flesh (fresh).
Liberty: Fall apple, high quality, red apple with crisp flavor (fresh or cooking).
Novaspy: Spy-type of fall apple (pies and other cooking).
Enterprise: Very late fall apple with uniform red color (fresh or cooking).
Goldrush: Very late fall apple with uniform yellow color (fresh or cooking).
Candycrisp: Very late fall apple with green color and very sweet flavor (fresh or cooking).
Crimson crisp: Fall apple with medium to dark red fruit (fresh).

Be aware that varieties resistant to apple scab might still be susceptible to other diseases and some fungicide and bactericide sprays might still be necessary. A list of cultivar susceptibility to other common apple diseases can be found in “Disease Susceptibility of Common Apple Cultivars” from Purdue University Extension. Also, consider the rootstock in your overall size of tree. A more dwarfing tree will allow for easier spray coverage and lend to the overall success of your backyard apple endeavor.

Source : msu.edu

Video: Why Your Food Future Could be Trapped in a Seed Morgue

In a world of PowerPoint overload, Rex Bernardo stands out. No bullet points. No charts. No jargon. Just stories and photographs. At this year’s National Association for Plant Breeding conference on the Big Island of Hawaii, he stood before a room of peers — all experts in the science of seeds — and did something radical: he showed them images. He told them stories. And he asked them to remember not what they saw, but how they felt.

Bernardo, recipient of the 2025 Lifetime Achievement Award, has spent his career searching for the genetic treasures tucked inside what plant breeders call exotic germplasm — ancient, often wild genetic lines that hold secrets to resilience, taste, and traits we've forgotten to value.

But Bernardo didn’t always think this way.

“I worked in private industry for nearly a decade,” he recalls. “I remember one breeder saying, ‘We’re making new hybrids, but they’re basically the same genetics.’ That stuck with me. Where is the new diversity going to come from?”

For Bernardo, part of the answer lies in the world’s gene banks — vast vaults of seed samples collected from every corner of the globe. Yet, he says, many of these vaults have quietly become “seed morgues.” “Something goes in, but it never comes out,” he explains. “We need to start treating these collections like living investments, not museums of dead potential.”

That potential — and the barriers to unlocking it — are deeply personal for Bernardo. He’s wrestled with international policies that prevent access to valuable lines (like North Korean corn) and with the slow, painstaking science of transferring useful traits from wild relatives into elite lines that farmers can actually grow. Sometimes it works. Sometimes it doesn’t. But he’s convinced that success starts not in the lab, but in the way we communicate.

“The fact sheet model isn’t cutting it anymore,” he says. “We hand out a paper about a new variety and think that’s enough. But stories? Plants you can see and touch? That’s what stays with people.”

Bernardo practices what he preaches. At the University of Minnesota, he helped launch a student-led breeding program that’s working to adapt leafy African vegetables for the Twin Cities’ African diaspora. The goal? Culturally relevant crops that mature in Minnesota’s shorter growing season — and can be regrown year after year.

“That’s real impact,” he says. “Helping people grow food that’s meaningful to them, not just what's commercially viable.”

He’s also brewed plant breeding into something more relatable — literally. Coffee and beer have become unexpected tools in his mission to make science accessible. His undergraduate course on coffee, for instance, connects the dots between genetics, geography, and culture. “Everyone drinks coffee,” he says. “It’s a conversation starter. It’s a gateway into plant science.”