Choose certain fruit trees to avoid pests, disease

I hope that readers with fruit trees are in the thick of winter pruning and thinking about that one crucial dormant oil application. For what dormant oil controls on fruit trees, the list is long and the price is low — as is the toxicity.

Because dormant oil is applied during dormancy — and most labels call for temperatures in the 40s — the beneficial insects that you would want to protect are generally absent. As a pest prevention method, it doesn’t get much better than that.

Except when it does.

How about some varieties that need little to no disease control? Depending on the fruit you would grow, Extension research offers answers based on what pests are most serious in your location.

The Purdue Extension publication Disease Susceptibility of Common Apple Cultivars helps you to sort the disease resistance of nearly 90 commercial apple cultivars. Want to grow some of those tasty Galas? They’re in the “very susceptible” categories for both apple scab and fire blight, which are devastating. Better choices for our area are Enterprise, Liberty or GoldRush.

GoldRush was developed in a program that combined the apple breeding talent at Purdue, Rutgers and the University of Illinois. And it’s tasty.

You may have to dig deeper for disease-resistance recommendations for other fruits, but they can be found. The key is to decide on your pest-resistance interests before you buy trees. Using that disease-susceptibility research can help to keep you from having to maintain a 10- to 14-day spray schedule to produce edible fruit.

If you know you don’t want to make pest control applications at all, you will be down to a handful of choices. Have a shopping list; you may need to use one of the mail-order nurseries to find those resistant cultivars.

Our earliest apples ripen in mid-July. One is William’s Pride, also resistant to scab, fire blight, rusts and powdery mildew. Our latest-bearing apples are those such as Granny Smith or Arkansas Black, which need a long growing season. Depending on your goals, you may wish to spread out the progress of ripening among your trees — or have a huge influx at a moment in the season that hands are free to pick and process.

If you are selling apples, how you will store and market them will help to determine harvest dates. That Gala — which I hope I have talked you out of based on disease susceptibility — has a short storage life, which means it must be sold and consumed fairly readily. The GoldRush and Arkansas Black have long storage properties. Given their late harvest, they may be stored for extended sale.

Getting back to that Gold Rush apple for a moment, what do I mean by tasty? Flavor and texture are subjective, so it’s important to know what you’re after. Also think about whether you are growing for fresh eating, processing or freezing. The very helpful “Apple Cultivars and Their Uses” from the University of Missouri Extension can help you to sort out each of these, and to cross-reference to harvest time and storage life as well as disease resistance.

If you will be planting new trees, please start with research that has already killed some trees on your behalf — so that you don’t have to. As always, feel free to contact Purdue Extension educators with any specific questions.

Kris Medic is Purdue Extension Bartholomew County’s educator for agriculture, natural resources and community development. She can be reached at 812-379-1665 or Send comments to