The stealthiness of predatory mites as spider mite biological control agents

Abstract

Adult spider mite females that are aware of predatory mites can reduce predation by dispersing from patches invaded by predators or by shifting their oviposition site onto webs where eggs are predated less than on leaf surfaces. Therefore, the stealthiness of predatory mites stalking spider mite females should largely determine the success of spider mite control. This study examined the stealthiness of three predatory mites: Phytoseiulus persimilis Athias-Henriot, Neoseiulus californicus McGregor, and Neoseiulus womersleyi Schicha. The first two species have been commercialized as spider mite biological control agents, whereas the last species is a native predator of spider mites in Japan. We measured two indices of predator stealthiness in bioassays using Tetranychus kanzawai Kishida as prey: the proportion of prey mites that dispersed from their patches in response to predator intrusion and the proportions of prey eggs laid on webs in response to predator eggs. Both indices resulted in the same ranking, with P. persimilis ranking highest and N. womersleyi lowest. The greater stealthiness of P. persimilis eggs compared with N. womersleyi eggs seemed to be due to the lower amount of detectable substances on the egg surface. We also measured this index of stealthiness for European and Japanese Tetranychus urticae Koch populations and found that they had the same 2 stealthiness ranking as measured using T. kanzawai. Therefore, we predict that the stealthiness of predatory mites is consistent across prey species and could be an effective index, along with conventional indices, for evaluating predatory mites as spider mite biological control agents. Keywords biological control agent ▪ Phytoseiulus persimilis ▪ Neoseiulus californicus ▪ Neoseiulus womersleyi ▪ Tetranychus kanzawai ▪ Tetranychus urticae

Cooperative Behaviors in Group-Living Spider Mites

“…females usually oviposit on the surface of leaf undersides. However, when they are threatened by specialist predatory mites that are well able to cope with webs (Sabelis and Bakker, 1992) and feed preferentially on spider mite eggs (Blackwood et al, 2001;Furuichi et al, 2005a), they disperse from invaded patches (Bernstein, 1984;Grostal and Dicke, 1999;Fernández-Ferrari and Schausberger, 2013;Hackl and Schausberger, 2014;Freinschlag and Schausberger, 2016;Otsuki and Yano, 2019) or oviposit on the webs instead (Oku and Yano, 2007;Lemos et al, 2010;Murase et al, 2017). For example, in environments with T. kanzawai eggs on and off the web, the predatory mite Neoseiulus womersleyi largely refrains from killing eggs on webs.…”

Predator‐ and killed prey‐induced fears bear significant cost to an invasive spider mite: Implications in pest management

“…Predator–prey interactions affect the life‐history traits and behavioral strategies of species involved, 1–4 resulting in demographic changes in these species 5 . Plant‐feeding mites can detect predation risk through chemical cues from predators and killed conspecifics, and respond accordingly 6–18 .…”

Spider mites avoid caterpillar traces to prevent intraguild predation

“…Spider mites prevent attacks by generalist predators using their protective webs 28 – 31 . They also prevent attacks by specialist predators that penetrate the webs by dispersing from invaded patches 18 , 19 , 32 , 33 or by seeking refuge and laying eggs on webs that cannot be easily accessed by the predators 34 – 38 . However, spider mites would be defenceless against large caterpillars that incidentally, rather than intentionally, consume spider mites along with host plant leaves 6 .…”