Temporal effects of threecornered alfalfa hopper (Homoptera : membracidae) girdling on translocation in soybean

The temporal effects of 1-, 7-, and 14-d old Spissistilus festinus (Say) petiole girdles on trans location in soybean (Glycine max (L.) Merrill) were investigated using the systemic herbicide glyphosate as a tracer. Leaves of S. festinus-girdled , steam-girdled, and ungirdled petioles were treated with glyphosate. Diffusive resistances, leaf temperatures, and stem growth rates of treated plants were compared with those of untreated plants to detect trans location of the herbicide. S. festinus girdles initially blocked trans location. Blockage was followed by recovery of phloem function in <7 d. Resumption of trans location was not due to apoplastic transport.