Infochemical use by predatory mites of the cassava green mite in a multitrophic context

D. Gnanvossou

Research output: Thesisinternal PhD, WU

Abstract

This thesis describes research on multitrophic interactions in a system consisting of (1) cassava plants ( <em>Manihot esculenta</em> ), (2) three herbivorous mites, i.e. the cassava green mite <em>Mononychellus tanajoa,</em> the red spider mite <em>Oligonychus gossypii</em> and the two-spotted spider mite <em>Tetranychus urticae</em> and (3) two exotic predatory mites <em>Typhlodromalus manihoti</em> and <em>T. aripo</em> , <em></em> in Africa. The objectives are to understand how the two exotic predators (i) exploit chemical information to locate the target prey in pure and mixed odors conditions with the alternative prey mites, (ii) perform when feeding on different prey mite species and (iii) interact with each other.</p><p>The predatory mites, <em>T. manihoti</em> and <em>T. aripo</em> were attracted to cassava leaves infested by <em>M. tanajoa</em> compared with non-infested leaves, when the predators were starved for 2, 6 or 10 hours. They were not attracted to 400 female <em>M. tanajoa</em> removed from infested plants nor to mechanically wounded leaves. In a choice situation, <em>T. manihoti</em> and <em>T. aripo</em> preferred odors from leaves infested by <em>M. tanajoa</em> to odors from leaves infested by <em>O. gossypii</em> regardless of the ratio <em>M. tanajoa</em> : <em>O. gossypii</em> . When <em>M. tanajoa</em> -infested leaves and <em>T. urticae</em> -infested leaves were offered in a choice situation, the response of the two predator species depended on the density of <em>T. urticae</em> . <em>Typhlodromalus manihoti</em> and <em>T. aripo</em> were attracted to odors from cassava leaves infested with both <em>M. tanajoa</em> and <em>O. gossypii</em> or to a mixture of odors from leaves infested with <em>M. tanajoa</em> and odors from leaves infested with <em>O. gossypii,</em> when compared to odors from non-infested leaves. In contrast, mixed odors from <em>M. tanajoa</em> -infested leaves and <em>T. urticae</em> -infested leaves did not yield a preference over odors from non-infested leaves.</p><em><p>Typhlodromalus manihoti</em> and <em>T. aripo</em> had a higher intrinsic rate of population increase (rm) and net reproduction (Ro), and a shorter generation time and doubling time on when they were feeding on <em>M. tanajoa</em> than on <em>O. gossypii</em> or <em>T. urticae</em> . Prey-related odor preference matched predator performance if the key prey is compared to the two inferior prey mite species.</p><em><p>Typhlodromalus aripo</em> displayed a marked preference for odors emitted from either infested cassava apices or infested young cassava leaves over infested old cassava leaves but showed equal preference for odors from apices and young leaves both infested with <em>M. tanajoa</em> . <em>Typhlodromalus manihoti</em> did not discriminate between volatiles from the three infested cassava plant parts. This mirrors the differential distribution of the two predators on cassava plant foliage.</p><p>Carnivorous arthropods when searching for adequate food and habitat for themselves and their progeny should in the meantime avoid becoming food for other organisms. Intraguild interactions have been investigated for the predatory mite species <em>T. manihoti</em> , <em>T. aripo</em> and the native species <em>Euseius fustis</em> . <em>Typhlodromalus manihoti</em> is able to discriminate between odors from patches with con- and heterospecific competitors and prefers to visit patches with heterospecifics. <em>Typhlodromalus aripo</em> preferred to move away from patches with heterospecifics or conspecifics. <em>Euseius fustis</em> avoided odors from patches with conspecifics as well as odors from patches with the heterospecifics <em>T. manihoti</em> and <em>T. aripo</em> .</p><p>In conclusion, this thesis shows that the distribution and diversity of prey species, intraguild predation and competition are likely to play an important role in infochemical use by <em>T. manihoti</em> and <em>T. aripo</em> . In addition to predator-prey interactions, interactions between predators can also be considered as important factors affecting population dynamics of both prey and predators.</p>
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Wageningen University
Supervisors/Advisors
  • Dicke, Marcel, Promotor
  • Hanna, R., Promotor, External person
Award date21 Jan 2002
Place of PublicationS.l.
Print ISBNs9789058085689
Publication statusPublished - 2002

Keywords

  • cassava
  • mites
  • phytoseiidae
  • predators
  • attractants
  • volatile compounds
  • manihot esculenta
  • mononychellus tanajoa
  • host parasite relationships
  • food chains

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