Research
Blue-light disco for fruit flies
Jennifer Ekman explores some grisly ideas on how to lead pests into a fun place with flashing lights , where they will meet with a sticky end .
Fruit flies rely on their eyes to find food , mates and hosts in which to lay their eggs . They search for visual cues , including colour and shape , and have been demonstrated to be either attracted to , or repelled by , certain colours .
Attract-and-kill devices such as “ Ladd ” and “ Fruition ” traps effectively use reflected light and aroma to lure flies to a sticky death . In the case of the Fruition trap , its cobalt blue colour is believed to resemble the waxy , ultravioletlight-reflecting bloom on the surface of rainforest fruits – the ancestral host of the Qfly .
But what about light itself ? Many insects are attracted to artificial light sources , especially nocturnal fliers such as moths and beetles . Lights that emit large amounts of UV radiation are generally the most attractive . So , for example , “ Bugzappers ” use UV light to attract insects , then electrocute them .
UV lights work because insects see using a wider range of wavelengths of light than us humans . Most insects have compound eyes with peaks in sensitivity in UV , blue and green wavelengths – whereas humans see in blue , green and red . Bees , for example , use UV light reflectance to find specific flower species . Some mono-colour flowers may look uninteresting to us , but have bright patterns , targets or ‘ landing strips ’ when seen using UV wavelengths 1 .
Manipulating UV light can help to manage some insect populations . Pests such as thrips , whiteflies and aphids use UV light to find hosts , and are attracted to high UV areas . Covering greenhouses with UV absorbing materials can reduce the number of thrips and aphids entering the crop 2 , particularly if they block wavelengths below 380nm 3 .
Other research has tested using green or yellow LED lighting in orchards to suppress the activity of heliothis moths . When the moths encounter light above a certain brightness their eyes lose their night adaptation . This means their normal nocturnal behaviours – flying , mating and eating – are significantly reduced 5 . LED lights are energy-efficient and inexpensive to buy , so could allow such methods to be used in orchards .
Traps using UV light can monitor what species are present as well as provide information on the relative density of different populations 4 . UV light traps have also been used as mass trapping devices to control pests , although with more variable results . One successful example is the management of rice stem borers in Japan
18 Australian Stonefruit Grower | April 2017 summerfruit . com . au