Overview
- What pests affect apples?
- Codling moth
- Oriental fruit moth
- Aphids
- Sooty blotch and flyspeck
- Spotted tentiform leafminer
- European red mite
- Brown marmorated stink bug
- Apple maggot
- Apple scab
- European apple sawfly
- How do I manage apple pests?
- Summary
Apples are a major global crop that contributes significantly to the economies of many countries, including India and the U.S. These countries produce approximately 2.2 and 4.5 million tonnes of apples per year, respectively. However, about 20% of apple crops in India are lost due to apple insect pests. In the U.S., millions of dollars are lost due to the activities of individual pests, such as the brown marmorated stink bug. This article focuses on apple tree pests and diseases, and discusses approaches to combating these threats, including the use of biological methods.
What pests affect apples?
Apples are attacked by a wide range of pests, including the larval stages of various moth and fly species, stink bugs, and aphids. They are also vulnerable to infections caused by several fungal species. Some of the damage caused by these diseases and pests is cosmetic. However, many pests feed on apple fruit, which can result in rotting and loss of yield.
Codling moth (Cydia pomonella)
This is a species of moth that damages apple trees during its larval phase. Adults are light grey or brown and have a wingspan of about 1 cm. Males have a distinctive line of shiny scales at the end of their wings. Larvae are pink with dark brown/red heads and grow to 1.27 cm in length. Larvae tunnel through apples to the core, where they feed on seeds, leaving visible holes. Frass (excrement) may be present.
Oriental fruit moth (Grapholita molesta)
This moth species damages apples and other fruit trees during its larval stage. Adults are grey with a 5 mm wingspan. Larvae progress through four or five developmental phases. They have pinkish bodies with brown or red heads and grow up to 13 mm in length. Larvae feed on shoots, twigs, and fruits of apple trees. Damage can appear as shoot wilting and the appearance of lateral shoots. Larvae follow a wandering path while feeding and do not always focus on the core.
Aphids (Dysaphis plantaginea, Eriosoma lanigerum)
Apple plants are vulnerable to attack from different aphid species. Rosy apple aphid (Dysaphis plantaginea) adults are light purple and pinkish and grow to between 2 and 3 mm in length. These aphids inject toxic saliva as they feed on leaves, which causes leaf curling and stunts fruit growth. These aphids produce honeydew, which promotes the growth of sooty mould. Woolly apple aphids (Eriosoma lanigerum) appear in shades of red, brown, and purple but are typically covered in a woolly white secretion. These aphids damage twigs and roots, and symptoms include the presence of galls (enlarged areas) in these areas.
Sooty blotch and flyspeck
These are diseases that cause discolouration of apple fruit that is close to maturing. Sooty blotch refers to dark brown or black areas that start small but can eventually cover the entire fruit. Many species of fungi cause this disease (including Phyllachora pomigena, and it is more severe in cool, wet weather. Flyspeck is also a fungal disease and is caused by the species Schizothyrium pomi. This disease appears as small black dots on apple skin. Importantly, both of these infections are limited to the outer surface of the apple and can be removed.
Spotted tentiform leafminer (Phyllonorycter blancardella)
This pest is a species of moth that damages plants during its larval phase. Adults have light brown wings with lateral white stripes and are 3mm long. Females lay creamy eggs on the undersides of leaves. Larvae are yellowish-green and progress through five developmental stages. The first stage feeds on sap from leaves, while later stages mine into leaves and feed on tissue. Damage appears as small areas of discolouration and “buckling” at the site of damage.
European red mite (Panonychus ulmi)
These mites cause damage to apple tree leaves by piercing plant cells with their mouthparts and feeding on tissue. Adults, eggs, and developmental stages are all red, except for just before moulting when instars are green. Damage appears as leaf discolouration or “bronzing”. In severe infestations, leaves can drop off prematurely.
Brown marmorated stink bug (Halyomorpha halys)
This pest causes damage to apple trees by feeding during its developmental and adult phases. They have a characteristic brown “shield-shaped” body and grow to 1.7 cm in length. It pierces plants with its “straw-like” mouthpart and feeds on fluids. In apples, this pest causes dimpling and fruit discolouration. The absence of feeding larvae can help to distinguish them from other pests.
Apple maggot (Rhagoletis pomonella)
This pest is a species of fly that lays its eggs inside the skin of apples. The adult apple maggot fly is about 6.35 mm long. They have clear wings with dark markings and characteristic white stripes on the abdomen (females have four, males have three). Larvae feed on apple fruit and burrow through the pulp. Damage appears as misshapen fruit and rotten, discoloured pulp. Tiny holes where females lay eggs may also be seen.
Apple scab (Venturia inaequalis)
This is a fungal infection caused by a species called Venturia inaequalis. Symptoms of infection include discolouration of leaves and fruit in small, lighter green or yellow patches. This can progress until entire leaves turn brown or black. Fruit can develop a dark, corky appearance. The fungus can live through the winter on fallen leaves and thrives in warm and wet conditions.
European apple sawfly (Hoplocampa testudinea)
This species of fly causes damage to apple plants during its larval phase. Adult flies are orange-brown with transparent wings and have a similar appearance to wasps. Larvae are creamy-white with a black head and burrow inside the fruit, and they begin feeding just under the skin. Symptoms of damage appear as spiralling shapes in the skin. Exit holes may appear as larvae migrate to nearby fruit, and frass may also be visible.
How do I manage apple pests?
There are several methods for managing pests that damage apple plants. A combination of approaches using integrated pest management practices and biological control methods often works well in many cases.
Monitoring
Watch carefully for the symptoms described above. You may need a handheld lens to see some of the smaller pests, like the European red mite. Fruit discolouration, particularly black or dark brown spots, is a common symptom associated with the pests we have discussed. In some cases, pest damage may be easily visible, such as exit holes made by larvae and frass. A high number of adult pests in the growing area can also indicate an infestation. An increased presence of ants may suggest an aphid infestation.
Cultural control
Cultural control involves using specific farming or gardening practices to lower the risk of pest infestations. This method of crop management depends on correctly identifying apple insects and diseases. Clearing the growing area of plant debris can reduce the abundance of fungal diseases such as apple scab. Planting orchards in areas with good drainage and air circulation may also prevent fungal growth. Remove fallen and rotting apples from the growing area. Avoid using them for composting near the area where they are grown, as this can encourage the growth and spread of pests and diseases.
Biological control
- Natural Substances: These are typically derived from plants and can be used in sprays to repel or kill pests. For example, natural pyrethrin, which is found in some flowering plants, can be effective in managing the apple maggot. The best time to spray is often after petal fall.
- Semiochemicals: These are messaging compounds that can be used to disrupt pest behaviour. For example, Isomate C TT and AO Midori Cydia pomonella Feromona contain coddling moth pheromones and can be used to lure this pest into traps.
- Microbials: These are microorganisms like bacteria, fungi, and viruses that harm pests but not crops. For example, Beauveria bassiana is a species of fungus that can help to combat the brown marmorated stink bug.
- Macrobials: These are larger animals, like certain insects, that feed on or parasitise pests. For example, Amblyseius andersoni is a predatory mite that feeds on the European red mite.
Chemical Pesticides
As a world leader in nature-based pest management knowledge implementation, CABI encourages Integrated Pest Management (IPM) as the preferred, ecologically-based approach to producing healthy crops, which allows for chemical pesticide use only as needed, and when adhering to measures that limit the exposure of people and the environment to them (see FAO, International Code of Conduct on Pesticide Management).
Before considering the use of chemical pesticides, farmers should explore all available non-chemical control solutions, such as the ones listed above.
In case chemical pesticides are considered for use, farmers should look to select lower-risk chemical pesticides which, when used as part of an IPM strategy, help manage pest problems while minimizing harmful effects on human health and the environment. Agricultural advisory service providers can provide information on lower-risk chemical pesticides that are locally available and are compatible within an IPM strategy. These experts can also advise on the required personal protective equipment.
Summary
Apples are vulnerable to a wide range of insect pests and fungal diseases that can significantly impact crop yield and quality. Key pests include codling moths, aphids, and stink bugs, while diseases like apple scab and sooty blotch also pose risks. Effective management relies on early monitoring, cultural practices, and strategies such as biological control using natural substances, microbials, and predatory insects to help reduce pest populations sustainably.
For tailored pest management advice, visit the CABI BioProtection Portal, where you can enter your location and pest problem to explore customised solutions.
For more information on apple tree care, refer to our comprehensive fact sheet on apples, which provides essential tips and guidance for maintaining healthy and productive trees.
We have also prepared extensive management guides for dealing with pests like aphids and protecting specific crops, including mango and pineapple.
