Ten years ago, scab fungus and too many bugs to count made my first attempts at growing organic apples a flop, particularly with New England’s favorite apple variety — the scab-prone ‘Macintosh’. Today, the Macs we grow at Lost Nation orchard in New Hampshire, literally shine in their unblemished skins as a testament to the integrated approach that has evolved with my understanding of orcharding.

The first point to keep in mind is that few gardeners face all of the apple pests that fill growers’ manuals, and that home gardeners need only concern themselves with a few key problems and the best methods for managing them. Below we describe specific stages of apple tree development and the important tasks for each period. We also discuss five of the most common pests.

No treatise on organic growing is complete without emphasising the importance of building rich soil. Your plantings rely on the billions of microorganisms teeming in good compost. In late fall or early spring, spread an inch or two of compost within the tree’s drip line.

Test the pH of your soil, and if it’s acidic, use either a ground limestone or powdered oyster shell to raise soil pH to between 6.3 and 6.8. If the pH tests within that range and if a soil test shows that soil calcium is low, use gypsum. A plentiful supply of calcium in soil is important to prevent bitter pit, a physiological disorder of apples.

Apple Pests

Three diseases and three insect pests most often ruin home apple crops. The diseases are apple scab, powdery mildew, and cedar-apple rust. The insect pests are codling moth, apple maggot, and curculio. Scab, powdery mildew, and codling moth are nearly universal; others are more regional.

Scab is generally considered the most serious apple disease. Initially the fungus causes olive green spots, which darken and harden over time. Scab develops in the mild temperatures and high humidity of spring. During particularly wet summers, subsequent scab infections, called “secondary scab,” will cause problems through the summer if you were unsuccessful preventing infection in spring.

Powdery mildew is common to many kinds of plants besides apples. Infected leaves are covered with a thin layer of white fungus. The disease develops fastest when days are warm and nights cool. It does not require high humidity. Spores overwinter in already infected buds.

Cedar-apple rust. This pest is aptly named because quarter-inch pustules on leaf undersides look just like spots of rust. Primarily a pest in the East, it can also occur in the Northwest. Two sulfur sprays beginning at pink bud control it, along with scab and powdery mildew. The spores spread to apple trees from red cedars up to 2 miles away. For spores to germinate, apple leaves must remain wet for four to six hours. Control it with the same sulfur spray you use for scab and powdery mildew, being sure to apply it at pink-bud stage and again three weeks after petal fall.

Stage 1: Dormant

• In fall, rake and clean below your tree to minimise overwintering scab disease. Or scatter ground limestone over the leaves to hinder scab reproduction and to maintain optimum soil pH.
 
• Prune your tree in March, while still dormant and shortly before spring growth begins. Prune to open the tree to air and light, a key to disease prevention. Remove prunings from garden area to prevent rot spores from establishing on cut branches.
 
• Order supplies for the coming season. More often than not, organic alternatives are available only from mail-order sources.