At a glance: Avocado is an important crop, but pests like thrips, lace bugs, and scale insects can damage it. Biological control methods, such as neem oil sprays and predatory mites, help control pest numbers and protect crops.
Overview
- What pests affect the avocado?
- Avocado lace bug
- Avocado thrips
- Laurel wilt disease
- Redbay ambrosia beetle
- Western avocado leafroller
- Florida red scale insect
- Avocado bud mite
- How do I manage avocado pests?
- Summary
- FAQ
The avocado is an important agricultural crop that contributes to the economies of many countries, particularly in tropical regions. The United States produces about 400 million pounds of avocados each year. However, this crop is vulnerable to damage from many insects and diseases which reduce yields and marketability. This blog focuses on identifying and controlling common avocado pests, including the use of biological methods.
What pests affect the avocado?
Avocados are vulnerable to attack by a wide range of pests, including thrips, spider mites, scale insects, and moth species. Laurel wilt disease is carried by the redbay ambrosia beetle and also contributes to significant crop loss. The California avocado industry has lost 35% to 45% of its market value in recent years due to avocado thrips alone.
Avocado lace bug (Pseudacysta perseae)
This pest is a small flying insect that attacks avocado leaves during its adult and developmental (nymph) stages. Adults measure around 2 mm long, are oval-shaped, and dark brown with lighter areas on the legs, wings, and abdomen. Adults lay eggs on the undersides of leaves in black globs of excrement that may look like black pepper grains. This pest sucks sap from the undersides of leaves. Damage appears as brown and tan spots on leaves and can cause premature leaf drop-off in severe cases, exposing the plant to sunburn and further damage.
Avocado thrips (Scirtothrips perseae)
Avocado thrips are pests that damage avocado leaf tissue by feeding on it directly. They also feed on immature fruit, which can cause fruit scarring. Adults are about 0.7 mm long and are typically orange or yellow with three characteristic red dots on the top of their heads. Females lay eggs on the undersides of leaves and inside avocado fruit. After hatching, immature avocado thrips progress through two larval and two pupal stages. Leaf damage appears as discolouration and scarring on both sides of the leaf. While internal fruit is not damaged, scarring can cause downgrading and premature culling.
Laurel wilt disease (Raffaelea lauricola)
This disease is caused by a pathogenic fungus which is commonly transmitted to plants by the ambrosia beetle. Damage caused by this disease can appear as dark blue streaks on sapwood, wilting of upper leaves and can lead to complete crop loss. The presence of these symptoms near a dead or dying tree can help confirm the presence of laurel wilt disease.
Redbay ambrosia beetle (Xyleborus glabratus)
This beetle is native to Asia but has become a significant pest in the US. Adult beetles are slender, dark brown or black, and grow to about 2 mm long. Larvae are white with red-orange heads. Damage can appear as holes and sawdust tubes on the trunk, which are made up of wood and excrement. While this pest tunnels into avocado trees and feeds, its most damaging effect is through the transmission of laurel wilt disease.
Western avocado leafroller (Amorbia cuneana)
This pest (also referred to simply as “amorbia”) is a species of moth which causes damage to avocado plants during its caterpillar phase. Adults grow to about 2.5 cm in length and are typically orange/tan with darker markings. Eggs are green and oval-shaped and are laid on the upper side of avocado leaves in masses of up to 100 individual eggs. Mature caterpillars are dark green, while younger ones are more yellowish. Both stages feed on avocado leaves. The damage they cause may appear as holes in the leaves or a skeletonised pattern. The larvae often feed inside leaves that are tied together with silk.
Florida red scale insect (Chrysomphalus aonidum)
Avocado crops are threatened by a variety of scale insects, including the Florida red scale insect (also known as circular red scale). Adult females are round, about 2 mm wide, and are black or very dark red. Males are oval, about 1 mm long, and typically paler than females. This pest feeds on host plant leaves but can spread to fruit and trunks in severe cases. Damage appears as leaf yellowing and drop-off, and the insects may be visible as circular black spots.
Avocado bud mite (Tegolophus perseaflorae)
This tiny pest feeds on the leaves of avocado plants, causing significant damage to crops and yield. They are yellowish and measure around 0.15 mm long. Adults live for about three weeks, and females lay several hundred eggs in this time. They are not easy to see except with a handheld lens. Mite damage leads to misshapen, discoloured fruit. They feed on leaf buds, causing necrotic (dead) spots on leaves.
How do I manage avocado pests?
There are several methods available for managing avocado crop pests. A combination of approaches using Integrated Pest Management (IPM) practices and biological control methods works well in many cases.
Monitoring
Keep alert for the symptoms described above throughout the growing season. The most common symptom of a pest or disease problem is leaf discolouration, which may appear in yellow, brown, or darker shades. Some pests feed directly on leaves, so keep an eye out for signs of direct feeding or skeletonised patterns. Large numbers of redbay ambrosia beetles can indicate laurel wilt disease infection, especially if symptoms such as blue-black streaks are present. Eggs of several pests are laid on the underside of leaves, but have different appearances, so inspection with a handheld lens may help with identification.
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 the pest. Using coarse organic mulch may reduce the growth of pests like avocado thrips in their cocoon stage. Remove dead or fallen material from the growing area, as it can act as a breeding area for pests like the redbay ambrosia beetle. Take steps to optimise plant health, which helps to build their resistance to pest attacks.
Biological control
- Natural Substances: These are typically derived from plants and can be used in sprays to repel or kill pests. For example, neem oil from the neem plant can be used to help control avocado lace bugs and Florida red scale insects, while garlic extract can be used to control avocado thrips.
- Semiochemicals: These are messaging compounds that can be used to disrupt pest behaviour. For example, pheromones from the light brown apple moth can be used to disrupt the mating of this pest, which damages avocado and other crops, in the United States.
- Microbials: These are microorganisms like bacteria, fungi, and viruses that harm pests but not crops. For example, Bacillus thuringiensis is a species of bacterium that can combat a huge variety of pests in their larval stage, including western avocado leafrollers.
- Macrobials: These are larger animals, like certain insects, that feed on or parasitise pests. For example, Amblyseius andersoni is a predatory mite that can help to control avocado thrips numbers.
Chemical Pesticides
As a world leader in nature-based pest management knowledge implementation, CABI encourages 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. For tailored pest management advice, visit the CABI BioProtection Portal, where you can enter your location and pest problem to explore customised solutions.
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 minimising 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
Avocado crops play an important role in the economies of many countries. However, the yield and quality of avocado crops are severely affected by pests and diseases. Managing these threats depends on accurate identification and selecting appropriate measures. Institutions like the Tropical Research and Education Center within the Florida IFAS Extension (University of Florida) help to improve our understanding of avocado pests and develop better management strategies. Combining monitoring with cultural and biological control methods is an effective way to reduce the threat posed by pests and protect the local ecosystem. We have also prepared extensive guides on dealing with pests such as aphids and protecting specific crops, including tomato and mango.
FAQ
How do I get rid of bugs on my avocado tree?
Removing bugs from avocado fruit trees depends on correctly identifying the problem. Harmless insects require no additional action while pests may require targeted approaches outlined above. Visit the CABI BioProtection Portal for specific solutions.
What pest eats avocados?
Pests like avocado thrips feed directly on avocado fruit. Other pests may cause misshapen avocado fruit without directly feeding on it.
What can I spray my avocado tree with?
Many sprays with different active ingredients can be applied to avocado trees to help control pest numbers. However, it’s important to accurately identify the pest or disease before selecting a suitable spray.
How to get rid of avocado lace bugs?
You can spray your avocado tree with neem oil to help repel avocado lace bugs and slow their growth. Sprays that contain the beneficial fungus Beauveria bassiana can also be effective in controlling this pest.
