In the caring for apple trees section , I have included an organic spray program. It is designed to prevent most if not all of the pest insects and diseases listed below. The need for this complete spray program diminishes if you purchase apple varieties such as Liberty or Redfree, which have good resistance to most of the serious problems. If you have non-resistant apples, and you choose not to follow the spray program, you may find that your apple crop is blemished in various ways. You will still get edible apples, but they won’t look pretty and parts will need to be cut out when they are eaten.

Apple trees are affected by a number of very common problems. However, because of their large, nutritious apples, they are also affected by a number of more unique pests and diseases that zone in on these fruits.

Problems of Apple Trees
Symptoms	Probable Causes
Apples have worms	Apple Maggots
Small Brown Spots on Fruit	Black Rot
Tunnels inside of apples	Codling Moth
Tiny Pale-yellow Spots on Leaves	Cedar Apple Rust
Gray, Velvety Mold On Leaves	Powdery Mildew
Withered and Dead Blossoms	Fire Blight
Foliage curls, puckers, turns yellow	Aphids
Leaves Stippled Yellow, discolored and distorted, white dots appear	Mites
Twig Dieback; Foliage Loss	Scale
Leaf Buds and Early Bark Eaten	Weevils
Defoliated Tree; Egg masses appear on trunk and branches	Gypsy Moth Caterpillar
Apples Fall, Have Cuts in Skin	Plum circulio beetle
Olive Green Spots on Undersides of Leaves; leaves cracked and distorted; apples develop spots	Scab

Apples Have Worms
Apple Maggots - Although they are hard to detect on the outside, sometimes white worms eat the flesh inside maturing apples. These are apple maggots, the larvae of the apple maggot fly. They are white or yellowish and measure 1/4 inch long. The adult fly is also 1/4 inch long. It is black with yellow legs, and has yellow markings across the abdomen and bands that zigzag across the wings. These flies lay eggs in punctures in pear or apple skin. The best way to control apple maggots is to prevent the adult fly from laying eggs. Trap them with a commercially available sticky trap. These are made from a red ball or a yellow rectangle covered with sticky material. Hang these traps in target fruit trees in late June and remove them after harvest. Use two traps per tree for a dwarf or semi-dwarf and four traps for standard trees. Keep them clear of surrounding branches. Remove all fallen fruit immediately.

Tunnels in Apples
Codling Moths - A codling moth larva is 1 inch long and pink with a brown head. The adult is a grayish brown moth with lacy brown lines on its forewings and pale, fringed hind wings that span 3/4-inch. Adults lay white, flat eggs singly on leaves, twigs, or fruit buds. The larvae of codling moths tunnel their way through apples, eating as they go. Their presence is signalled by visible cocoons in bark crevices. To control these pests, spray dormant oil on trees prior to leaf budding in late winter or early spring to suffocate the eggs. As the blossoms are just beginning to open and show pink (this is called “open cluster”), set out commercial sticky traps with pheromone lures to catch the moths. If there are more than 10 moths caught in a single trap during the 10 to 14 days after bloom time use ryania in a spray as the blossom petals begin to fall. Spray BT and light horticultural oils every 7 to 10 days later in the season to kill newly hatched larvae. Plant butterfly weed (Asclepias tuberosa) nearby; it hosts parasites of codling moths.

Small Brown Spots on Fruit
Black Rot - A fungus, black rot does not become evident until a few weeks before fruit maturity or after harvest when it appears as storage rot. Black rot symptoms show on the apples. Small brown spots develop on the apples, frequently at a wound. They later expand and darken, finally turning black. Concentric zones of alternating shades of brown and black appear around these lesions. Minute black pimples may later develop as the apples shrivel and mummify. During the growing season, the fungus attacks bark, twigs, and fruit, and over-winters in these tissues. Use an approved fungicide as directed. Prune out infected wood and destroy mummified fruit.

Tiny Pale-yellow Spots on Leaves
Cedar Apple Rust - Cedar apple rust causes pale yellow, pinhead-sized spots on the upper surfaces of apple leaves. These spots enlarge and turn bright orange on foliage and fruit. This rust originates on nearby cedar trees, forming swellings, or galls, on their bark. Junipers and hawthorns can also spread cedar apple rust to apple trees. Spray apple trees with fungicide when cedar galls are releasing spores in the early spring. Remove all red cedar trees within 300 yards of the apple tree. Apple varieties resistant to Cedar Apple Rust include Liberty, Nova Easygro, Novamac, Priscilla, and Redfree.

Gray, Velvety Mold On Leaves
Powdery Mildew - Powdery mildew is a fungus that covers the tips of twigs, leaves, and blossoms with white to pearly gray velvety mold. Twigs are dwarfed, and the terminal bud is killed, which causes staghorn growth of side shoots. Young apples develop russeting or etching. To control powdery mildew, apply an approved fungicide, such as 95 percent flowable sulfur, before bloom and every other week until June 15 (as described in the spray program). Prune infected terminals for additional control. Mildew gets worse with periods of high humidity. You can prevent mildew problems by growing resistant apple varieties, spacing and pruning to improve aeration and reducing shade over the tree. Water early in the day, taking care to avoid wetting the foliage. Reduce nitrogen enriched feedings to avoid excessive late season growth. Resistant varieties include Akane, Delicious, Discovery, Golden Delicious, Liberty, Lodi, Macfree, Prima, Priscilla, Red Delicious, Redfree, Sir Prize, Spartan, and Tydeman’s Red.

Withered and Dead Blossoms
Fire Blight - Fire-blight fungus can be one of the most serious pests of apple trees. Very few trees are completely resistant and those that are usually produce poorer fruit. While it is a major problem, it is a disease that can be controlled with correct fertilization and pruning.

Shoots infected with fire blight turn brown or black as though scorched. The blossoms wither and die. Water-soaked reddish bark lesions appear, and on warm days they ooze an orange-brown liquid. Later they become brown and dry. The best defense against fire blight is diligent pruning. In the winter, look for affected branches with visible cankers, and prune them off just a few inches below the cankers. On limbs too large to remove, pare away diseased tissues, sealing the wounds with tree paint. In the summer, watch for blackened leaves, stems, or fruits, and cut them off 12 inches below any sign of disease. Also snap off vigorous suckers thrown up along branches and from the rootstock. These parts are very prone to fire blight. It is VERY IMPORTANT not to forget to disinfect your pruning tool in a bleach solution (one part household bleach to four parts water) after each cut! Hold the shears in the solution for at least 2 seconds to disinfect. Resistant varieties include Akane, Baldwin, Delicious, Liberty, MacFree, McIntosh, Northern Spy, Nova Easygro, Novamac, Prima, Redfree, Red Delicious, Winesap, and Stayman.