Reduced translucency and the addition of black patterns increase the catch of the greenhouse whitefly, Trialeurodes vaporariorum, on yellow sticky traps

Abstract

The greenhouse whitefly Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae) is a pest of a wide range of vegetable and ornamental crops in greenhouses around the world. Yellow sticky traps are highly attractive to flying adults and so are frequently used to monitor the pest. Our aim was to test whether changes in trap translucency or the addition of printed black patterns could increase the catch on yellow sticky traps in greenhouses. Field trials were carried out in commercial crops of strawberry and tomato under glass over three years. Reduced trap translucency increased trap catches by a factor of 1.5 to 7.0 and the catch increased significantly for both females and males. Spectrometer measurements showed that the increased catch was consistent with an increased landing stimulus from a colour opponency mechanism i.e. the ratio of energy from 500–640 nm to the energy from 300–500 nm. Printed black patterns increased trap catches on specific types of trap, by a factor of 1.4 to 2.3, and the catch increased significantly for both females and males. The patterns increased trap catch on moderately translucent traps, but decreased trap catch on less translucent traps. The evidence points to a contrast/edge effect of pattern, but laboratory experiments are needed to clarify this. Exploitation of these translucency and pattern effects could improve the efficacy of yellow traps for monitoring and mass trapping in crops.

Attributes of Yellow Traps Affecting Attraction of Diaphorina citri (Hemiptera: Liviidae)

“…Patterns with contrasting edges are considered to have a stimulatory effect on compound eyes and serve as the basis for potential attraction [ 44 ]. High-contrast edges can facilitate detection of visual targets by insects, as shown with stored product beetles [ 45 ] and whiteflies [ 23 ], in which vertical black stimuli elicited attraction behavior. Black patterns have also been reported to increase house fly attraction to sticky traps [ 33 , 34 ].…”

“…Characteristics of visual signals that affect attraction of insects to a target include hue, saturation, brightness, translucency, and polarization [ 20 , 21 , 22 , 23 ], with some possible effects from fluorescence or iridescence [ 23 , 24 , 25 ]. The size and shape of targets [ 26 , 27 , 28 ], as well as contrast to background [ 29 , 30 , 31 , 32 ], are important features affecting attraction of a wide range of insect species to monitoring traps.…”

“…The size and shape of targets [ 26 , 27 , 28 ], as well as contrast to background [ 29 , 30 , 31 , 32 ], are important features affecting attraction of a wide range of insect species to monitoring traps. The presence of black edges or patterns on visual targets may increase insect captures on traps, as seen with house flies [ 33 , 34 ] and whiteflies [ 23 ]. The length of contrasting edges on trap surfaces contributes to attraction of aphids and thrips [ 26 , 35 ].…”

Blue-green opponency and trichromatic vision in the greenhouse whitefly (Trialeurodes vaporariorum)

“…This has profound relevance for the basic understanding of the visual mechanism of Trialeurodes vaporariorum and provides the basis for the improvement of visual trapping methods for monitoring and control in greenhouses. A recent study already showed the effect of modifying the reflective properties of yellow card traps (Sampson et al, 2018). This can be further specified according to the determined wavelength and intensity dependence, the photoreceptor sensitivity estimations, and the colour choice model from our study.…”

“…The authors determined the spectral properties of the traps and explained the results on the basis of the potential blue-green opponency. The brighter reflection in the green-yellow range and the low transmission of blue light had a greater influence on the opponent mechanism, resulting in higher attraction (Sampson et al, 2018).…”