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Recognition behavior of the cassava mealybug Phenacoccus manihoti Matile-Ferrero (Homoptera:Pseudococcidae) at the leaf surface of different host plants
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Edité par CCSD ; Springer Verlag -
International audience. The testing behavior and test probing which are a part of host-plant acceptance behavior were studied in P. manihoti. Attention was focused on the testing behavior of three plants of the Manihot genus (Incoza, M'Pembé and Faux-caoutchouc) and a weed of the cassava fields (Talinum). This enabled us not only to characterize the associated behavior but also to show that the mealybug is able to distinguish between different host plants when walking on the leaf. The video description of the test probing of first- and fourth-instar larvae on M'Pembé and on the Faux-caoutchouc shows that the succession of the phases is similar. After a first phase characterized by the repeated intervention of the mealybug sensorial organs, a second phase, more mechanical, with up-and-down head movements, is observed. At this time, the stylets pass through the epidermic and inner tissues. Finally, a third phase, during which the mealybug becomes more agitated, is observed: it stands up using its rear legs and pushes the upper part of its body against the plant. The stylets continue their progression, which is principally intercellular, until they reach the phloem. Longer and longer immobility periods are observed over a period of time. We used the coupled videocamera and electrical penetration graph technique to see the relations existing between outer and inner plant events, i.e., between the behavioral items and the electrical signals characteristic of the stylets pathway in the plant. We observed that the stylet progression in the plant was more difficult in the resistant hybrid Faux-caoutchouc than in the sensitive M'Pembé variety.
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