Within-plant variation in nitrogen and sugar content of poinsettia and its effects on the oviposition pattern, survival, and development of Bemisia argentifolii (Homoptera: Aleyrodidae)
1995
Bentz, J.A. | Reeves, J. III. | Barbosa, P. | Francis, B.
More females of Bemisia argentifolii Bellows & Perring were found on young (nodes 3 or 4) and fully expanded mature leaves from the midregion (nodes 7 or 8), than on nonsenescence old leaves from the lower region (nodes 11 or 12) of single-stemmed vegetative poinsettias, Euphorbia pulcherrima Willdenow (Euphorbiaceae). Yet, more eggs were laid on mature and old leaves than on young leaves. More crawlers hatched from eggs laid on young or old leaves than on mature leaves. More crawlers reached the adult stage when reared on mature leaves than on young and old leaves. The protein nitrogen content of the leaves and the sugar content of the phloem were correlated with the amino nitrogen content of the phloem. Increased oviposition on mature and old leaves is correlated with the high nitrogen content of these leaf types compared with young leaves. Oviposition on mature leaves is clearly adaptive because survivorship of whiteflies is higher on these leaves. Leaf nitrogen content is probably the cue used by B. argentifolii to discriminate among leaf types within a plant. Whiteflies may use nitrogen concentration of the leaf tissue to assess indirectly the nitrogen content of the phloem because the two were correlated. Sugar concentration was correlated with amino nitrogen concentration in phloem. Phagostimulant dependence on sugar may elicit maximal settling and ingestion by whiteflies where amino acids are most likely to be in good supply.
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