Overview
- What are fruit flies?
- What are the different types of fruit flies?
- What is the impact of fruit flies?
- How do I know if I have a fruit fly problem?
- How do I get rid of fruit flies?
- Summary
Fruit flies are a diverse group of small flying insects that damage various crops in diverse geographical locations, including Bangladesh and the US. These pests are sometimes referred to collectively as exotic fruit flies and can devastate crop yield and lead to significant economic losses. Fruit flies cause damage to crops at both egg-laying and larval stages, attack a wide range of fruits and vegetables, and have been particularly devastating to mango crops in Bangladesh. This article will cover the different types of fruit flies, how they damage crops, and biological methods to identify, monitor, and control their numbers.
What are fruit flies?
There are many species and subspecies of fruit fly pests, each with a distinct appearance. However, they are all small, two-winged insects that are generally yellow-brown in colour. The specific appearances of economically important species are described below.
Lifecycle
The life cycle of fruit flies varies between species and climates. Generally, female fruit flies lay eggs underneath the skin of different fruits and vegetables, usually when they are ripe or close to ripening. When eggs hatch, the larvae begin feeding on plant tissue. Fruit flies progress through egg, larva, pupa, and adult phases with different durations depending on the species. Life cycles typically take 1-2 months, but adult flies of some species overwinter and live for up to 11 months in some cases. Females can lay hundreds or even thousands of eggs over their lifespan.
What are the different types of fruit flies?
Several species and subspecies of fruit fly pests damage different plants in different countries worldwide.
Mediterranean fruit fly (Ceratitis capitata)
Despite its name, the Mediterranean fruit fly is present in Africa, Asia, Australia, Europe, and the Americas. Its eggs are white and roughly 1 mm long, and larvae typically grow to 9 mm in length. Adults are 3-5 mm long, yellow-brown in colour, with dark red-purple eyes. Eggs hatch in 1.5 days, and larvae mature into adults in 2-4 weeks, depending on the season.
Mexican fruit fly (Anastrepha ludens)
This pest seriously impacts mango, grapefruit, and citrus fruit yields in Mexico, Central America, and the US. Eggs hatch after 1-2 weeks, and larvae grow to 12 mm long. Adult flies are 7-11 mm long, with a yellow-brown body, and distinctive pale yellow wing bands.
Oriental fruit fly (Bactrocera dorsalis)
The oriental fruit fly is native to Asia but is also present in Africa and the US. It has several other names, which were once thought to represent separate species: mango fruit fly (B. invaders), B. papaya, and B. philippinensis. Oriental fruit fly eggs are slender and white. Larvae are also white and grow to 11 mm long. The adult appearance differs across subspecies but typically has two distinctive black stripes across the abdomen. This pest is particularly destructive to mango and papaya fruits.
Caribbean fruit fly (Anastrepha suspensa)
These flies are closely related to Mexican fruit flies and damage a wide range of host plants in the Caribbean and Florida. Eggs hatch in 2-3 days, and the white larvae grow to about 10 mm and feed off plants for 1-2 weeks. Adults are yellow-brown and grow to about 14 mm with yellow-brown wind bands. Guavas and rose apples are particularly vulnerable to attack from this pest.
Queensland fruit fly (Bactrocera tryoni)
This is a serious pest across eastern Australia. Eggs are white and hatch after 1-2 days, depending on the season. Larvae feed for about three weeks, attacking plants like tomatoes, apples, and pears. Adults are wasp-like with yellow and dark brown markings and grow to about 8 mm long. The entire egg-to-egg life cycle of the Queensland fruit fly takes about six weeks.
The spotted-wing drosophila (Drosophila suzukii)
This species is native to Asia but has spread to Europe and the Americas. It has a wide range of hosts and is particularly problematic for cherries in Washington state in the US. Eggs are white and smaller than those of other species (around 0.5 mm long) but also hatch after 1-3 days. Spotted-wing drosophila larvae are white, while their pupae are dark brown, with both stages of development measuring approximately 3 mm long. Adults are also around 3 mm long, have red eyes, and are light tan in colour. Males have a characteristic dark spot near the tip of the wings, and adults typically live for 1-2 months or longer if they overwinter. This is a close relative of the species Drosophila melanogaster, which scientists use to study human disease genes, among other topics. Drosophila melanogaster is not considered a pest.
What is the impact of fruit flies?
Larvae feed directly on plant tissue, which causes fruit to become mushy, discoloured, and inedible. Fruit fly pests can feed on ripening or ripe fruits still attached to the plant. This distinguishes them from non-pest species that only feed on already spoiled plant tissue. Fruit flies cause significant economic damage to crop yield in different countries. In Bangladesh, reports suggest that 70% of the mango crop is threatened by fruit fly pests. In California alone, fruit fly crop damage is estimated at $25 billion. Countries put significant investment into fruit fly management solutions and detection programs, leading to further economic strain.
How do I know if I have a fruit fly problem?
The primary symptom of fruit fly damage is decaying and rotting fruit and vegetables. Monitoring adult fruit fly numbers is a great way to understand the extent of your problem (described below). Fruit fly damage can cause fruit to drop off the plant prematurely. Inspection of damaged fruit can reveal the presence of larvae. Larger fruit fly infestations can lead to a significant loss of yield and more excessive damage to plants across growing areas.
How do I get rid of fruit flies?
Monitoring
Adult fruit flies are typically monitored using traps, and larvae are monitored by sampling fruit. Semiochemicals often act as lures for traps in that case. Estimating adult fruit fly numbers and identifying their species is important for selecting appropriate control responses. Trapping is considered a type of mechanical control for different types of pests. However, it is used more frequently for fruit fly identification and monitoring than for population control. DIY fruit fly traps can trap and kill fruit flies, gnats, and other arthropods, though they are more suitable for small-scale or domestic infestations like kitchen fruit flies. To make a trap, put apple cider vinegar drops and dish soap in a jar trap, cover the opening with plastic wrap, and poke holes in the top. If the trap works, fruit flies will enter and be immobilised in the dish soap.
Biological control
Biological control involves harnessing naturally occurring organisms and substances to naturally manage pest populations in agriculture.
Microbials
These are microscopic organisms, such as viruses, bacteria, and fungal species, that can control pests. Metarhizium anisopliae is a species of fungus that infects and kills adult fruit flies. It does this by infiltrating fruit fly cells and causing cell death.
Macrobials
These are larger animals that reduce pest numbers in different ways. For example, parasitic wasps help control fruit fly populations by laying their eggs in fruit fly larvae and killing them during the pupal stage. This means a reduction in fruit damage will not be noticed until the next growing season.
Natural substances
Natural substances derive from plants and other natural sources and have a variety of anti-pest activities, such as killing and repelling insects. Pyrethrin is a natural substance obtained from a species of flowering plant that affects the nervous system of insects, ultimately killing them.
Chemical pesticides
As a world leader in nature-based pest management knowledge implementation, CABI encourages Integrated Pest Management 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. These might include cultural practices like collecting and destructing infested fruits and consulting the CABI BioProtection Portal for identifying and applying suitable biological control products.
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
Fruit flies are small, two-winged insects that damage ripe fruits, vegetables, and other organic matter. These flies significantly impact agricultural economies, such as mango production in Bangladesh and crops in the U.S. Fruit flies feed on plant tissue, causing fruits to rot and drop prematurely. Monitoring and control strategies include traps and biological methods like parasitic wasps and microbes. Integrated pest management approaches are becoming more popular due to their environmentally friendly nature and reduced reliance on harmful chemicals.
You can search for biological control solutions to your fruit fly problem using the CABI BioProtection Portal. Consider reading about other problematic pests and bioprotection more generally from our extensive resource library.
