Drosophila suzukii, Spotted wing drosophila

Spotted wing drosophila (SWD), Drosophila suzukii, occurs in Asia, Africa, Europe, Oceania and the Americas. It is a highly-invasiveand destructive pest ofberries and stone fruits, such as cherry, nectarine, apricot, plum, peach, strawberry and raspberry. Adults lay their eggs into semi-ripe and ripe fruits, and damage is caused by larval feeding and fruit rots due to secondary exposure to pathogens and other feeding insects. The larvae are difficult to target with pesticides and there are reports of up complete crop loss if left unchecked. Russell IPM offer a variety of traps and lures for monitoring and mass trapping as well as a general repellent as part of a push-pull strategy.

Adult female (left) and male (right) Drosophila suzukii

Biology

Adult male SWD are 2 to 3.5mm in length, with thick orange-brown bodies and bright red eyes. The abdomen is covered with thin horizontal bands. Wings are slightly grey and transparent.Within two days of emergence, male SWD develop a dark spot on each of their wings, visible with the naked eye. The males also have two sets of black tarsal combs on their forelegs.

Adult female SWD have larger abdomens than males and no wing spots. Females possess a serrated ovipositor (egg laying organ) to penetrate the skin of developing fruits in order to deposit their eggs.

Eggs are long and whitish, with thin white filaments extending from one end.

Larvae are creamy-white with small black spots marking the head. They reach 3.5mm in length.

Pupaeare creamy-yellow when new. Red eyes become visible during pupation, and mature pupae appear brown or orange-brown. At the head end of the pupae are two small stalks.

Life Cycle and Behaviour

SWD are reproductively prolific, achieving 13 generations per annum in favourable conditions. In optimal conditions, SWD can be active for 10 months of the year, before adults overwinter until the following year.

SWD can withstand cold winter temperatures and overwinter as adult flies
Oviposition (egg laying) occurs between spring and autumn
A single female can lay 7-16 eggs per day for 10-65 days
An average female will lay 195 eggs in her lifetime
Eggs hatch in 1-3 days
Larvae mature in 3-13 days, feeding within their hosts fruit
Larvae usually pupate in fruit but can drop off the host plant and pupate in soil
Pupae emerge from 4-43 days dependant on temperature

Nature of Damage

Female SWD puncture the surface of fruit in order to deposit their eggs, which are sometimes seen sunken into the fruit and surrounded by a brown or black marks. Larvae then hatch and feed on the fleshy pulp within fruitsleaving large sunken holes, diminishing their quality. Consequently, the fruit rots due to secondary exposure to pathogens and other feeding insects. Pupal cases can be seen sticking out of fruits, particularly in softer and smaller hosts. Other Drosophila species also lay their eggs within fruit punctured by SWD.

Monitoring

SWD traps and lures can be used throughout the year for mass trapping or for monitoring in order to help with decision-making.

Lures for pest monitoring

Lures

Russell IPM offers two lures that attract SWD.The two lure types give growers a choice in order to deliver a flexible, easy-to-use and reliable monitoring and trapping programme. The long-lasting, low-maintenance SWD blister pack lures are particularly convenient for trapping over winter between crops and for regular monitoring when combined with the red Impact trap. The liquid lure, MaxDro, is more suitable for mass trapping.

SWD Dry lureprovides continuous release of food attractant volatiles for up to 3 months, dependent on temperatures.The dry lure can be hung inside the lid of the Suzukii trap to achieve long-lasting mass trapping. It can be combined with either MaxDro or soapy water as a drowning solution. Alternatively it can be used with red Impact sticky boards, which are an easy to use and an effective monitoring tool for SWD, as the flies can be seen easily on the boards without sifting through liquid.
MaxDrois a liquid attractant that ensures a high capture of SWD and a relatively low catch of non-target insects. Maxdro is replaced every 2-4 weeks once the liquid has evaporated or solidified.

Lures Handling

Wear gloves to handle the lures and wash hands with fresh water after contact.

Lure Storage

SWD lure: Store in a cool dry place. Shelf life can vary from 6-12 months depending on the storage temperature.

MaxDro: Once the MaxDro bottle is opened, use within two weeks. See technical data sheet for further details.

Trap Selection

Russell IPM offers a choice of two trap types to suit purpose and preference.

Suzukii trap

The Suzukii trap is a robust trap for mass trapping SWD

Red colour is highly attractive to SWD
Versatile, can be used with SWD blister pack lures and/or MaxDro liquid lure
Multiple entry points to maximise SWD trap catch
Tapered entry points to reduce non-target species
Flat bottom for easy stacking and storage
Robust, weatherproof, re-usable trap

Red Impact board sticky trap

The red impact board makes identification of male SWD easy, eliminating the need to sieve through liquid. Red is a highly attractive colour for SWD, and coupled with the SWD dry lure the Russell IPM red Impact traps are a practical, easy to use solution to SWD monitoring.

Use with SWD dry lure (lures can be moved between traps until the liquid runs out)
Ready to use
Male SWD are easily identified at first glance
Available with grid pattern for ease of counting
Easy and effective monitoring
Early warning indication of pest build up

Trap Density

Before cropping, place 80-100 Suzukii traps per hectare around the edge of the crop at 2-10m intervals. As the cropping season progresses, increase the trap density and move traps into the crop, using one trap per 200m². Traps and lures can also be placed in woodland areas overwinter to reduce overwintering SWD populations.

Trap Position

Hang the trap on a branch or crop wire at mid canopy height near fruit, in shaded areas in top or bush fruit. Place just above canopy height in strawberry.

Data and Interpretation

Monitor for SWD throughout the year. They migrate to nearby dense hedgerows and woodlands to overwinter when fruit crops are unavailable.

Set and maintain traps around the perimeter of the crops in early season to reduce invasion into the crop early in the season.

If SWD are present in the traps around the perimeter when the fruit is developing, then two traps per hectare should be added inside the crop roughly 10 m from the perimeter, in order to test how well the control methods are working.

Decisions on pesticide application should not be taken solely on the trap catch data. Climatic and biological considerations should be taken in account.