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Trophic relationships between predators, whiteflies and their parasitoids in tomato greenhouses: a molecular approach

Published online by Cambridge University Press:  07 February 2012

R. Moreno-Ripoll
Affiliation:
IRTA, Entomology, Ctra. de Cabrils, Km. 2, E-08348 Cabrils, Barcelona, Spain
R. Gabarra
Affiliation:
IRTA, Entomology, Ctra. de Cabrils, Km. 2, E-08348 Cabrils, Barcelona, Spain
W.O.C. Symondson
Affiliation:
Cardiff School of Biosciences, Biomedical Sciences Building, Cardiff University, Museum Avenue, Cardiff, CF10 3AX, UK
R.A. King
Affiliation:
Cardiff School of Biosciences, Biomedical Sciences Building, Cardiff University, Museum Avenue, Cardiff, CF10 3AX, UK
N. Agustí*
Affiliation:
IRTA, Entomology, Ctra. de Cabrils, Km. 2, E-08348 Cabrils, Barcelona, Spain
*
*Author for correspondence Fax: (34) 93 7533954 E-mail: nuria.agusti@irta.cat
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Abstract

The whiteflies Bemisia tabaci Gennadius and Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae) are two of the main pests in tomato crops. Their biological control in Mediterranean IPM systems is based on the predators Macrolophus pygmaeus (Rambur) and Nesidiocoris tenuis Reuter (Hemiptera: Miridae), as well as on the parasitoids Eretmocerus mundus (Mercet) and Encarsia pergandiella Howard (Hymenoptera: Aphelinidae). These natural enemies may interact with each other and their joint use could interfere with the biological control of those whitefly pests. Analysis of predator-prey interactions under field conditions is therefore essential in order to optimize whitefly control. Species-specific polymerase chain reaction (PCR)-primers were designed to detect DNA fragments of these whiteflies and parasitoids within both predator species in tomato greenhouses. We demonstrated that both predators feed on both whitefly species, as well as on both parasitoids under greenhouse conditions. Prey molecular detection was possible where prey abundance was very low or even where predation was not observed under a microscope. Whitefly DNA detection was positively correlated with adult whitefly abundance in the crop. However, a significant relationship was not observed between parasitoid DNA detection and the abundance of parasitoid pupae, even though the predation rate on parasitoids was high. This unidirectional intraguild predation (predators on parasitoids) could potentially reduce their combined impact on their joint prey/host. Prey molecular detection provided improved detection of prey consumption in greenhouse crops, as well as the possibility to identify which prey species were consumed by each predator species present in the greenhouse, offering a blueprint with wider applicability to other food webs.

Information

Type
Research Paper
Copyright
Copyright © Cambridge University Press 2012
Figure 0

Table 1. Prey, parasitoid and predator species tested for cross-amplification using whitefly and parasitoid specific primers described in table 2.

Figure 1

Fig. 1. Amplification products obtained with the specific primers for the four target prey. Lane 2, Bemisia tabaci (158 bp); 3, Trialeurodes vaporariorum (187 bp); 4, Eretmocerus mundus (345 bp); 5, Encarsia pergandiella (314 bp). Lane 1, 100 bp DNA ladder.

Figure 2

Table 2. Whitefly and parasitoid species-specific primer sequences (5′–3′), amplified fragment sizes and gene targeted.

Figure 3

Table 3. Predator and prey abundances (mean±SE) in eight tomato greenhouses.

Figure 4

Table 4. Predated prey observed under microscope (mean±SE) and percentages of positive M. pygmaeus and N. tenuis by PCR in eight tomato greenhouses.

Figure 5

Table 5. Molecular detection percentages of all prey combinations within M. pygmaeus and N. tenuis.

Figure 6

Fig. 2. (a) and (b) Relationship between percentages of whitefly detected in both predator species and whitefly adult presence; and (c) and (d) whitefly pupae presence.

Figure 7

Fig. 3. Prey molecular detection percentages within M. pygmaeus and N. tenuis from greenhouse H. *, significant difference between M. pygmaeus and N. tenuis. Bt, B. tabaci; Tv, T. vaporariorum.