Biological control of thrips and whiteflies by a shared predator: Two pests are better than one

Abstract

Biological control of thrips and whiteflies by a shared predator: Two pests are better than one Messelink, G.J.; van Maanen, R.; van Steenpaal, S.E.F.; Janssen, A.R.M. General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. AbstractWe studied the capacity of one species of predator to control two major pests of greenhouse crops, Western flower thrips (Frankliniella occidentalis (Pergande)) and the greenhouse whitefly (Trialeurodes vaporariorum (Westwood)). In such a one-predator-two-prey system, indirect interactions can occur between the two pest species, such as apparent competition and apparent mutualism. Whereas apparent competition is desired because it brings pest levels down, apparent mutualism is not, because it does the opposite. Because apparent competition and apparent mutualism occurs at different time scales, it is important to investigate the effects of a shared natural enemy on biological control on a time scale relevant for crop growth. We evaluated the control efficacy of the predatory mites Amblyseius swirskii (Athias-Henriot) and Euseius ovalis (Evans) in cucumber crops in greenhouse compartments with only thrips, only whiteflies or both herbivorous insects together. Each of the two predators controlled thrips, but A. swirskii reduced thrips densities the most. There was no effect of the presence of whiteflies on thrips densities. Whitefly control by each of the two predators in absence of thrips was not sufficient, yet better with E. ovalis. However, whitefly densities in presence of thrips were reduced dramatically, especially by A. swirskii. The densities of predators were up to 15 times higher in presence of both pests than in the single-pest treatments. Laboratory experiments with A. swirskii suggest that this is due to a higher juvenile survival and developmental rate on a mixed diet. Hence, better control may be achieved not only because of apparent competition, but also through a positive effect of mixed diets on predator population growth. This latter phenomenon deserves more attention in experimental and theoretical work on biological control and apparent competition.

Pest species diversity enhances control of spider mites and whiteflies by a generalist phytoseiid predator

“…In the latter case, predator satiation results in a short-term positive indirect interaction between its prey species. With respect to biological control, some studies have indeed demonstrated that the control of a pest species can be improved by the presence of another pest species (Collyer 1964;Karban et al 1994;Liu et al 2006;Messelink et al 2008), whereas disruption of biological control through predator satiation in the shortterm has also been demonstrated (Koss and Snyder 2005;Symondson et al 2006). So far, both theory and experiments on the effects of a shared predator have ignored the effects of a mixed diet on predator populations.…”

“…Hence, the presence of several prey species can increase predator populations through the increased availability of food as well as through the higher quality of a mixed diet. Based on these mechanisms, pest species diversity in combination with predators attacking various prey species can enhance biological control (Messelink et al 2008).…”

“…The predatory mite A. swirskii has proven to be an effective control agent for thrips (Messelink et al 2006) and whiteflies (Nomikou et al 2001(Nomikou et al , 2002, whereas its effect on spider mites is still unclear. Moreover, control of whiteflies is improved when thrips are present in low densities (Messelink et al 2008). Although A. swirskii does feed on spider mites (Momen and El-Saway 1993), greenhouse observations suggest that the webbing produced by spider mites impedes effective control because A. swirskii is not able to enter it (Messelink, personal observations).…”

Alternative food and biological control by generalist predatory mites: the case of Amblyseius swirskii

“…This lack of food will cause the predators to switch to feeding on the pest. Furthermore, predators sometimes perform better on a mixed diet than on single diets (Messelink et al 2008); hence, they may actually prefer feeding on both alternative food and target prey. A further question is how to supply the alternative food.…”

“…It was collected from the field (Nomikou et al 2001) and tested for its capacity to control whiteflies (Nomikou et al 2001(Nomikou et al , 2002(Nomikou et al , 2004, and was subsequently found to be able to control thrips as well (Messelink et al 2006). Further research showed that this generalist can effectively control both pests at the same time (Messelink et al 2008;Calvo et al 2011) and has potential to control other pests as well (Wimmer et al 2008;Arthurs et al 2009;van Maanen et al 2010;Park et al 2010). This has ignited significant interest in this predatory mite, which is increasingly used for biocontrol (estimated at 30,000 ha worldwide; Knapp and van Houten, Pers Comm, 2015), and is currently subject of much research (over 80 publications during the last 6 years, over 50 during the last 3 years; Web of Science TM ).…”