Feeding and Oviposition Behavior of Whiteflies (Homoptera: Aleyrodidae) Interpreted from AC Electronic Feeding Monitor Waveforms

Abstract

Electronic waveforms produced by feeding and oviposition activities of two whitefly species, Parabemisia myricae (Kuwana) and Bemisia argentifolii Bellows & Perring, generally were similar but had some subtle differences. Stylet penetration almost always started with a sawtooth waveform (repetitious, large-amplitude waves with a frequency ranging from 0.05 to 0.5 Hz) that was correlated (via styletectomy and light microscopy) with intercellular penetration by the stylets through the epidermis, mesophyll, and vascular tissue. Occasionally during stylet penetration, when whiteflies were producing sawtooth waveforms, stylet advancement stopped, the stylets were retracted slightly and then advanced into a new direction, leaving behind an empty salivary sheath. This was correlated with a sudden decrease in voltage level during the sawtooth waveform. Ingestion from phloem sieve elements was correlated with a high-flat waveform (steady high voltage level with little voltage fluctuation). Phloem ingestion always was preceded by ≤3 min of sawtooth waveforms followed by a brief transition waveform that occurred between the sawtooth and high-flat waveforms. The transition waveform is analogous to the aphid X-wave. P. myricae and B. argentifolii took an average of 24 and 16 min, respectively, from initiation of a penetration to phloem ingestion. A low-flat waveform (steady low voltage level with little voltage fluctuation) was correlated with ingestion in some cases, but ingestion during this low-flat waveform probably was not from phloem sieve elements. The low-flat waveform may indicate more than one biological process. Oviposition by both whitefly species produced a distinctive two-phase waveform; the first phase was correlated with penetration of the ovipositor into the leaf and the second phase was correlated with insertion of the egg pedicel into the leaf.