Does marking with fluorescent powders affect the survival or development of larval Vanessa cardui?

Many investigations of insect behavior, physiology, dispersal, population size, biological control, and conservation require the marking of individuals. Studies have used a wide variety of marking methods (see reviews in Akey, 1991; Southwood & Henderson, 2000; Hagler & Jackson, 2001; and in the special issue of International Journal of Pest Management introduced by Lavandero et al., 2004), ranging from sophisticated expensive methods, like molecular markers or radar, to simpler inexpensive approaches such as abrasion or paints. One of the most common methods of externally marking insects (Hagler & Jackson, 2001) is to dust them with micronized particles of fluorescent dye (known as fluorescent powder or dust). Available in a wide variety of colors, these powders have been used to mark many insect taxa. Unlike some marking methods, fluorescent powders can be applied to larval insects as well as to adults. A good marking technique should not affect the survival or behavior of marked individuals (Southwood & Henderson, 2000). Some studies that use dusted insects simply assert that fluorescent powders have no adverse effects. However, numerous studies provide quantitative data on behavior or survival of dusted insects relative to undusted control groups, despite Parker’s (2005) assertion that no such accounts have been published. Examinations of the possible effects of dusting on behavior have focused on movement and on insects’ response to pheromones. In studies of corn rootworm beetles by Naranjo (1990) and Toepfer et al. (2005) and of trichogrammatid wasps by Garcia-Salazar & Landis (1997), only one of the multiple dusted groups examined showed a reduced tendency to fly. Cook & Hain (1992) observed a small reduction in the percentage of dusted bark beetles that initiated flight, but did not analyze this difference statistically. Nakata (2008) found that dusted psyllids took longer to initiate flight toward a light. Dusting had no significant effects on flight behavior of planthoppers (Cronin, 2003). Though field mark-recapture studies are sometimes used to infer the effects of dusting on movement, such studies typically conflate survival and movement differences, and are not reviewed here. In three studies of responses of dusted and undusted insects to pheromones (bark beetles: Cook & Hain, 1992; spruce budworm: Kipp & Lonergan, 1992; diamondback moths: Mo et al., 2003), dusting had no effect. Overall, negative effects of dusting on behavior were reported in only a small subset of the conditions tested. Compared with behavioral studies, there have been far more investigations of the effect of dusting on survival. Most found no significant differences between the survival rates of dusted groups and undusted controls (Drosophila pseudoobscura Frolova & Astaurov: Crumpacker, 1974; Drosophila simulans Sturtevant: Moth & Barker, 1975; mountain pine beetles: McMullen et al., 1988; corn rootworm beetles: Naranjo, 1990; OloumiSadeghi & Levine, 1990; boll weevils: Reinecke, 1990; spruce budworms: Kipp & Lonergan, 1992; phlebotomine flies: Pardo et al., 1996; trichogrammatid wasps: Garcia-Salazar & Landis, 1997; planthoppers: Cronin, 2003; diamondback moths: Mo et al., 2003; cicadellids: Coviella et al., 2006; psyllids: Nakata, 2008). Additionally, Oloumi-Sadeghi & Levine (1990) determined that dusting adult corn rootworm beetles had no effect on their rates of ovarian development. However, other studies of survival, sometimes using the same insect species as above, documented adverse effects of fluorescent powder dusting. Dye et al. (1991) *Correspondence: E-mail: bierzych@lclark.edu