To determine whether sodium sulfite or EDTA was responsible for the reduction in transmission efficiency, virions were purified with only EDTA or sodium sulfite as additives and transmissibility was determined. When only EDTA was added, the purified virus was transmissible at levels similar to virus prepared with neither of the additives, 92% compared to 95%, respectively (Table 1 ). In contrast, the sodium sulfite treatment reduced transmissibility to ,5%. The negative impact of sodium sulfite on virus transmission by aphids was independent of virus concentration since the results were consistent across four independent experiments where the 