Apple tree

The apple tree belongs to a genus of small deciduous trees or shrubs of the rose family.

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Photo: PlantEnPlagen

Apple tree (Malus domestica) belongs to a genus of small deciduous trees or shrubs of the rose family. Malus includes the apple tree and ornamental apples. The apple grows in the temperate climate zone. The tree generally blooms from mid-April to the end of May. Apple blossom and the young fruits are sensitive to frost damage.

Apples are ready to pick when you can bend or twist the apple on the tree. When it’s easy to bend or twist, then the apples are ready to pick. As apples ripen, the seeds turn from white to black: apples with brown seeds are ready to pick; those with black seeds ready to eat.

Bugs

recognize aphids
Aphids, photo: Luc Viatour – CC BY-SA 3.0

Deformed and crumpled leaf: aphid.

Dot-shaped spots on the leaf; mites on the underside: Red spider mite (Tetranychus urticae).

Feed on the budding buds and young leaves: caterpillars of the winter moth (Operophtera brumata).

Elstar infested by codling moth caterpillar, photo: PlantenEnPlagen

Worm-eaten fruits early in spring, red spot around the borehole: codling moth (Cydia pomonella).

recognize caterpillars on pear tree
Spinning of a Little Ermine in pears tree, photo: Dennis Schuitema

Spiders with orange caterpillars between the leaves: larvae of the Little Ermine (Swammerdamia pyrella), an ermine moth.

White fluff from the Woolly apple aphid on apple, photo: Abrahami – CC By-SA 2.5

White sticky fluff, later followed by galls and woody outgrowths: Woolly apple aphid (Eriosoma lanigerum).

Recognize damage to apple ovary
Apple Sawfly larva borehole, photo: University of Maine

Early in spring 2 mm large pale green caterpillar-like larvae with a black head, later brown, at the newly formed apples.
Holes of 2 to 3 mm in the apple with orange-brown apple pulp around the drill hole: larvae (caterpillars) of the apple sawfly (Hoplocampa testudinea).

Apple leaf sawfly Caterpillars, Photo: Glorie Koen

Pale green caterpillars feed on the leaf margins. The caterpillars have a row of shiny black dots on the side: Apple leaf sawfly (Pristiphora maesta).

recognize aphids on apple tree
Green aphids on growing shoots, photo: Frederik Ceyssens

Green aphids on new shoots – especially in summer. The new shoots curl through the aphids and are somewhat inhibited in growth. In early spring they are only slightly visible: Green apple aphid (Aphis pomi) .

recognize wart-like elevations on apple
Wart-like elevations on ripening apples (Elstar), photo: PlantEnPlagen

Rough elevations appear on ripening apples: Common green capsid (Lygocoris pabulinus). Can’t hurt, only the skin of the apple is a bit affected.

Fungi & diseases

recognize Brown rot
Brown rot, photo: PlantenEnPlagen

Brown coloring apples with fungal spores: Brown rot (Monilinia spp.).

recognize apple scab
Apple scab, photo: PlantenEnPlagen

recognize apple scab
Light green, matt spots on the leaves due to apple scab, photo: CC0 Public Domain

From light green to brown discolouring spots on the leaf, apples stop growing, get dark spots with star-shaped cracks: apple scab (Venturia inaequalis) .

recognize difference between Dowry Mildew and Powdery Mildew
Downy and Powdery mildew on grape leaf, photo: Agne27 – Public Domain

Fungus on young leaves and blossom: Powdery mildew (Ascomycota phylum) or Downy mildew, a water mould (Peronosporaceae).

recognize nectria canker
Nectria canker, photo: Abrahami – CC BY-SA 3.0

Bark tears, branch withers and red fungal fluff appears: Nectria canker (Neonectria ditissima).

recognize apple canker
Rotten spots on apples, apple canker, photo: Dominique Bauwens

Rotten spots on apples; sometimes around the stem and sometimes at the nose: Apple canker (Neonectria ditissima).

recognize fire blight
Apple with fire blight, photo Paethon – CC BY-SA 3.0

Blossom, leaf, branch and twig turn brownish-black and thickened spots shrivel: fire blight (Erwinia amylovora).

A colorful collection of grown twigs: witches broom (Taphrina betulina).

recognize Bull’s eye rot
Bull’s eye rot on Golden Delicious, photo: Davy Vansimsen

A red dot develops on the skin of the apple during storage or in storage, which quickly enlarges and develops into a round brown spot: Bull’s eye rot (Neofabraea spp.).

Other

Burr knots on the trunk of an apple tree, photo: Angela Dijkgraaf

Small root tips are formed on the trunk. A moist environment, prolonged rain and a lot of shade promote the development of burr knots. Trees with burr knots are more susceptible to fire blight and Nectria canker since the root tips provide many gateways for bacteria and fungal spores. In dry and sunny weather, cut out the burr spots generously and cover with wound balm.

Wasps on Pear, Photo: PlantenEnPlagen

Wasps sometimes attack fruit.

Brown, sunken spots, Photo: Rasbak – CC BY-SA 3.0

Deepened, brown spots on the apple. Under those spots, the apple is brown and corky; the spots often taste bitter. Mostly caused by calcium deficiency .

Voles can cause damage to the roots of shrubs and trees
Vole, photo: Susette Smeets

No leaves on young apple trees; the roots are eaten away: voles .

Stains on apple, golden reinet, sunscreen
Brown spots (sunburn) on Goudenreinet, photo: Roelfina Van de Weg

During hot summer weather (temperatures above 30ºC), red spots appear on the ripening apples: sunburn .

recognize damage to branches
Bare-eaten branches of a young fruit tree, photo: Jess (Rural Dreams)

In winter, hares, rabbits and roe deer sometimes like to gnaw on the branches and trunk of the apple tree.

Causes of trunk tear
Vertical crack in the trunk of an apple tree, photo: Tuinadvies.nl

Vertical cracks in the bark of the trunk: frost cracks.

Recognize lichen on apple tree
Parmelia, a foliose lichens on the branches of an apple tree, photo: PlatenEnPlagen

Lichen on the branches.

recognize frost damage to apple tree
Pale brown spots, dried buds due to frost damage, photo: Steven Henderickx

In early spring: buds dried up, pale brown spots on young leaves: damage from spring frost.

Recognize late blooming apple
Apple tree blooms for the second time. Photo: Alexandrina Gillis

After the spring, when the apples start to grow, the tree blooms sometimes with some blossom here and there. Remove this blossom, preferably before the flowers have opened. This blossom does not lead to fruit but might form an entrance for fire blight.

recognize drought damage apple
Leaf of apple tree withers, photo: Elly Beintema

In a period of summer heat and drought, the leaves dry out: drought damage.

Recognizing glassiness in apples
Glassy, translucent patches around the core, Photo: Facebook

Glassy, translucent spots appear in the flesh around the core: the cells leak cell fluid: Watercore. In severe cases, the glassiness has progressed to the point where it is visible on the skin and the apple will turn brown inside. The cause is often calcium deficiency, which means that the apple is unable to convert sugars into starch. A frugal use of nitrogen fertilizers helps to prevent watercore. See also calcium deficiency.

recognize June onion
An abundance of fruits, photo: JN Smit

Fruiting follows after flowering of the fruit trees. Usually there is an excess of small fruits. Between the end of May and mid-June, however, many apples fall off: the June drop. A natural process in which the tree rejects all weak fruits. See also fruit thinning .