Drosophila suzukii, commonly known as spotted wing fly (DAM), is a pest of great relevance to fruit growing due to its impact on several thin-skinned fruit crops.
Common names
- Spotted-wing fly (DAM)
- Spotted Wing Drosophila (SWD)
Crops attacked
The spotted wing fly infests a wide variety of fruits, especially those with thin skin, including: blackberry, guava, raspberry, guava, blueberry, strawberry and Surinam cherry.
Biology
Drosophila suzukii, unlike other species of the genus Drosophila, is capable of attacking fruits that are still intact. This characteristic is due to the highly serrated ovipositor (egg-laying structure) of the females, which allows them to pierce the skin of healthy fruits to lay eggs.
The life cycle of d.suzukii varies according to temperature and food availability. Under favorable conditions, it can complete a cycle in 10 to 15 days, allowing several generations to occur over the course of a single harvest. The cycle includes the following stages:
- Egg: white and elongated, measuring about 0,6 mm, and deposited inside the fruit. It has two respiratory filaments that project out of the shell.
- Larva: It is cylindrical and whitish in color. It feeds on the pulp of the fruit, causing it to deteriorate. The larvae go through three instars before pupation.
- Pupa: It can develop both inside the fruit and in the soil, close to the host plants. It is light brown in color and measures approximately 3 mm.
- Adult: small, measuring 2 to 3 mm in length, it has red eyes and a yellowish to light brown body. Males have characteristic dark spots on their wings, while females have a serrated ovipositor.
Temperature directly influences the development and reproduction rate of d.suzukii. In warm climates, the cycle is shorter, favoring a rapid population increase. At temperatures below 10°C, development is reduced and adults may enter diapause.
Females can lay 300 to 600 eggs throughout their life, which can last between 20 and 60 days, depending on environmental conditions. This high reproductive potential favors the spread of the pest.
Ecology and characteristics
Drosophila suzukii It originates in Asia and has spread globally due to the fruit trade and favorable climatic conditions. It is currently present in several regions of the world, including North America, Europe and South America, where it represents a threat to commercial fruit farming.
The species adapts well to temperate and subtropical climates, and is found in fruit-growing areas, especially in regions of moderate altitude, where humidity favors its survival.
The female identifies ripe fruit through chemical and visual stimuli. She uses her ovipositor to pierce the skin and lay eggs inside the fruit. A single female can infest multiple fruits, making the spread of the pest rapid and difficult to contain.
The adults of d.suzukii They are highly mobile and can fly short distances in search of new hosts. However, their main form of dispersal is through the transport of infested fruits. Furthermore, in protected environments, such as greenhouses, the pest can remain active throughout the year.
Factors that influence its abundance:
- Temperature: mild climates favor the pest; in extreme temperatures (above 30°C or below 0°C), its survival is reduced.
- Humidity: high relative humidity (above 60%) favors the development of larvae and the longevity of adults.
- Food availability: ripe or maturing fruits are the main targets. The presence of fruit residues in the field can contribute to the maintenance of populations.
Damage
Primary damage is caused by the female during oviposition and by larvae that feed on the pulp of the fruits, leading to their collapse and making them unfit for consumption. Secondary damage occurs due to the development of microorganisms, such as fungi and bacteria, which accelerate the decomposition of the fruits.
Control
For effective management of Drosophila suzukii, the following strategies are recommended:
- Traps: use fly traps baited with a mixture of biological yeast, sugar and water, strategically positioned in the cultivation areas. Replace the attractant every 15 days and eliminate the collected material.
- Cold storage: keep harvested fruits at temperatures below 5°C to reduce pest development and reduce damage during marketing.
- Frequent harvesting: carry out regular harvests, preventing ripe fruits from remaining on the plants or falling to the ground.
- Biological control: although parasitoid insects have already been recorded d.suzukii in Brazil, its effectiveness is still limited. The use of entomopathogenic fungi, such as beauveria bassiana, may be an alternative, and applications should be carried out at the end of the day and periods of treatment with fungicides to control diseases in plantations should be avoided.
- Chemical control: apply products during periods of greatest pest activity, generally in the morning (7am to 9am) and afternoon (15pm to 18pm). It is essential to check which molecules are authorized for the target crops before application and to rotate chemical groups to avoid the development of resistance.
- Waste disposal: Collect and dispose of unsuitable fruits, carrying out heat treatment (solarization) before disposal. Store the waste in sealed plastic bags and expose them to the sun for at least 24 hours before disposal in compost bins.
- Management: avoid cracking in the fruits through adequate irrigation practices. Prevent mechanical damage during cultural treatments.
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