Abstract
Glasshouse tomato production is reduced by the whitefly Trialeurodes vaporariorum, a major worldwide pest of glasshouse crops. Whitefly control is achieved using pesticides or parasitoids, which have drawbacks. There is thus a need for other control methods. For instance, the use of volatile compounds from plant odours could profoundly change the behaviour of plant-eating insects. This practice should be safe because plant odours are usually harmless to humans. Therefore, we have studied the effect of plant volatiles on whiteflies feeding on tomato plants. The rationale was to use the confusion effect by supplying whiteflies with a super-abundance of volatiles. We removed plant headspace volatiles from multiple whitefly host plants. Then, we presented these volatiles to whiteflies feeding on tomato plants. At the same time, whitefly stylet penetration is monitored using electrical penetration graphs (EPG). Plant colonisation, egg laying and honeydew production are analysed in separate experiments. Data are compared to controls in which extracted volatiles from tomato and air alone are presented to the whiteflies. The only significant effect produced by exposure to multiple-host volatiles is a pronounced reduction in the incidence of phloem-related waveforms during the 15-h EPG recording. This represents a delay in, rather than a cessation of, phloem-related activities as there is no related reduction in long-term performance. The confusion effect thus does not appear to exert strong effects on whitefly behaviour here.
Highlights
The glasshouse whitefly, Trialeurodes vaporariorum, is a major worldwide pest of glasshouse crops with control in the glasshouse usually achieved by chemical or biological means (Fig. 1)
Both control methods have their drawbacks, and here, we begin to investigate the possibility of supplementary control using harmless plant volatiles that may fundamentally alter the behaviour of insect plant pests
The positive relationship between reaction time to find a focal object and the number of items in the set containing the focal object has been used to derive influential models of visual search such as the Feature Integration Theory (Treisman and Gelade 1980; Wolfe et al 2010). This idea is embodied in the Neural Limitations Hypothesis (Dall and Cuthill 1997; Bernays 2001), stating that plant-eating insects specialise to increase the accuracy of plant location and selection behaviour
Summary
The glasshouse whitefly, Trialeurodes vaporariorum, is a major worldwide pest of glasshouse crops with control in the glasshouse usually achieved by chemical or biological (typically parasitoids) means (Fig. 1) Both control methods have their drawbacks, and here, we begin to investigate the possibility of supplementary control using harmless (to humans) plant volatiles that may fundamentally alter the behaviour of insect plant pests. A few studies have investigated the relationship between plant species complexity and whitefly plant utilisation efficiency (Bernays 1999; Smith et al 2001; Bird and Krüger 2007; Roff et al 2012; Mansour et al 2012), and most indicate that, at least for some performance parameters and host plant mixtures, plant diversity negatively impacts whiteflies. While we believe the confusion effect is the most likely explanation for the modest negative effects of mixed host volatiles we observe here, as Bernays (1999), we are cautious in attributing them solely to the confusion effect and discuss other mechanisms that could contribute
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