Witting-Bissinger BE, Orr DB, Linker HM. Effects of floral resources on fitness of the parasitoids Trichogramma exiguum (Hymenoptera: Trichogrammatidae) and Cotesia congregata (Hymenoptera: Braconidae). Biological Control
(Impact Factor: 1.64).
11/2008; 47(2):180-186. DOI: 10.1016/j.biocontrol.2008.07.013
This study was conducted to determine if floral resources enhanced longevity and fecundity of the egg parasitoid Trichogramma exiguum Pinto & Platner and longevity of the larval parasitoid Cotesia congregata (Say). Newly eclosed (⩽12 h) female wasps were provisioned with fennel (Foeniculum vulgare P. Mill.) or buckwheat (Fagopyrum esculentum Moench) flowers or one of two controls: honey or water. Wasps were monitored daily until all had died. Daily egg production by T. exiguum was monitored using Ephestia kuehniella Keller egg cards. Longevity of both T. exiguum (6.7 d) and C. congregata (5.1 d) provided buckwheat flowers was increased approximately 8.5-fold compared with wasps provided only water. Buckwheat-provisioned T. exiguum exhibited 2-fold greater longevity than those provided fennel. Longevity of C. congregata provisioned with fennel and honey was not statistically different. Water-provisioned T. exiguum and C. congregata exhibited the shortest longevity (0.8 and 0.6 d, respectively). Total fecundity was 6.3-fold greater in T. exiguum provisioned with buckwheat and 2.3-fold greater in T. exiguum provisioned with fennel than in water controls. Average female to male ratio of progeny over the lifetime of each female was significantly greatest in T. exiguum provisioned with water alone, likely because of sperm depletion in wasps exhibiting greater longevity. Total mean number of female offspring produced was significantly greatest in T. exiguum provided honey or buckwheat flowers although no difference in total female offspring were observed between adults provisioned with buckwheat or fennel flowers. Our results show that provisioning T. exiguum with honey and buckwheat flowers resulted in greater longevity, total fecundity, and lifetime production of female offspring than water alone. Buckwheat flowers also lead to greater longevity in C. congregata.
Available from: Mathias Kölliker
- "Although I. amara was as attractive as C. cyanus, it would clearly be less efficient in enhancing M. mediator in the field because it is not a suitable food source (Géneau et al. 2012). Fagopyrum esculentum in contrast is a very good food source for M. mediator, and numerous laboratory studies (Araj et al. 2011; Géneau et al. 2012; Lavandero et al. 2006; Nafziger and Fadamiro 2011; Winkler et al. 2006; Witting-Bissinger et al. 2008) and field studies (Hogg et al. 2011; Lavandero et al. 2005; Lee and Heimpel 2005, 2008; Platt et al. 1999; Scarratt et al. 2008) have demonstrated its value for enhancing natural enemies. However it is less attractive than both C. cyanus and I. amara, so it seems less efficient at attracting M. mediator in an environment where it is not the only flower available—which would be the case in a wildflower strip composed of multiple flowers or in/around cabbage fields where other weeds are growing. "
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ABSTRACT: In agricultural landscapes, the lack of floral nectar can be a major difficulty for nectar feeding parasitoids. This problem can be reduced by the addition of suitable wildflowers. To date, flowers have mainly been studied in terms of effects on parasitoid fitness, not taking into account the essential role of flower attractiveness for foraging parasitoids. This study experimentally tested the olfactory attrac-tiveness of five wildflowers (bishop's weed, corn-flower, buckwheat, candytuft, and oregano) to the parasitoid Microplitis mediator (Haliday) (Hymenop-tera: Braconidae). We conducted choice experiments in a Y-tube olfactometer to test the attractiveness of flowers against air, and relative attractiveness in paired choice tests. Our results showed that all the flowers were highly attractive and that in paired choice tests cornflower and candytuft were equally attractive and more attractive than buckwheat. These results indicate that M. mediator has evolved innate preferences that could be effectively exploited in biological control.
Available from: ee.oxfordjournals.org
- "It is possible that natural enemy diversity had a stronger relationship with natural pest suppression compared with other broad scale variables measured because our measurement of natural enemy diversity captured sources of variation (e.g., habitat fragmentation) that were not directly measured but related to the diversity of natural enemies associated with each site. Floral resources typically have a number of positive effects on natural enemies ranging from increased longevity (Orr and Pleasants 1996, Witting-Bissinger et al. 2008) to higher fecundity (Idris and GraÞus 1995, Tylianakis et al. 2004, Lee and Heimpel 2008). As a result, the presence of ßoral resources often augments natural enemy abundance and diversity and can increase rates of predation and parasitism (Stephens et al. 1998, Collins et al. 2002, Frank and Shrewsbury 2004, Ellis et al. 2005). "
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ABSTRACT: The role biodiversity plays in the provision of ecosystem services is widely recognized, yet few ecological studies have identified characteristics of natural systems that support and maintain ecosystem services. The purpose of this study was to identify landscape variables correlated with natural pest suppression carried out by arthropod natural enemies, predators and parasitoids. We conducted two field experiments, one observational and one experimental, where landscape variables at broad and local scales were measured and related to natural pest suppression. The first experiment measured natural pest suppression at 16 sites across an urban to rural landscape gradient in south central Wisconsin. We found natural enemy diversity positively affected natural pest suppression, whereas flower diversity negatively affected pest suppression. No relationship was found between natural pest suppression and broad scale variables, which measured the percentage of different land cover classes in the surrounding landscape. In the second experiment, we established small (2- by 3-m) replicated plots that experimentally varied flower diversity (0, 1, or 7 species) within a plot. We found no significant relationship between natural pest suppression and the different levels of flower diversity. The fact that we only found differences in natural pest suppression in our first experiment, which measured natural pest suppression at sites separated by larger distances than our second experiment, suggests the more appropriate scale for measuring ecosystem services performed by mobile organisms like insects, is across broad spatial scales where variation in natural enemies communities and the factors that affect them become more apparent.
Available from: David G. James
- "Buckwheat (cv. Ikeda) Fagopyrum esculentum Moench was chosen because previous studies have demonstrated that the incorporation of this plant within crops led to increased abundance and fitness of natural enemies, higher parasitism rates and lower pest abundance (Berndt, Wratten & Hassan 2002; Lavandero et al. 2005; Lee & Heimpel 2005; Begum et al. 2006; Irvin et al. 2006; Witting-Bissinger, Orr & Linker 2008). Buckwheat has quick germination and short sowing to flowering time (Bowie, Wratten & "
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ABSTRACT: 1. An increase in pesticide resistance in many pest species is promoting interest in biological control. Much remains to be learned about natural enemy immigration into and persistence within crops at specific times and how to maximize suppression of pest populations. Therefore this study was conducted to test a novel biological control approach, ‘attract and reward’ which combines two aspects of applied insect ecology: synthetic herbivore-induced plant volatiles (HIPVs) to improve immigration of beneficial taxa into crops and nectar plants to maintain their populations.
2. The ‘attract and reward’ approach was tested in sweetcorn, broccoli and wine-grapes with several HIPV formulations at 1·0% (v/v) as attractants and buckwheat (Fagopyrum esculentum Moench) as reward. Abundance of insects was assessed with non-attractive sticky traps for up to 22 days after the HIPV spray application.
3. In sweetcorn, Eulophidae were more numerous in the attract treatments: methyl anthranilate, methyl jasmonate (MeJA), methyl salicylate (MeSA) and HIPV mix. Encyrtidae were more abundant near MeJA-treated plants. In broccoli, Scelionidae were more abundant in MeSA treatments with reward and near cis-3-hexenyl acetate-treated plants without reward whilst Ceraphronidae were more numerous near MeSA and predators were more abundant near HIPV mix-treated plants. Nectar plant reward increased catches of parasitoids from several families in all three tested crop species and increased predators in sweet corn and broccoli.
4. Increases in natural enemy numbers were correlated with effects at the first and second trophic levels. Significantly fewer larvae of the sweetcorn pest Helicoverpa spp. were found on sweetcorn plants from plots with reward and significantly less Helicoverpa spp. damage was evident to cobs for one of the HIPV treatments.
5. Synthesis and applications. Results suggest that applications of synthetic HIPVs can enhance recruitment of natural enemies and buckwheat was a suitable resource subsidy plant for increasing abundance and residency. Whilst both of these approaches offer potential to enhance biological control, further work is required to realize fully synergistic effects from their combination as an ‘attract and reward’ approach.
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