Influence of Sucrose Concentration on Diet Uptake and Performance by the Pea Aphid, Acyrthosiphon pisum1

Abstract

Sucrose at a concentration of 10% and above in a chemical diet was phagostimulatory to 1st-stage nymphs of the pea aphid, Acyrthosiphon pisum (Harris) (Homoptera: Aphididae). The total amount of sucrose ingested during the 1st 24 hours (hr) increased with the rise from 5 to 50% sucrose concentration in the diet, but diet uptake in microliters per aphid was highest when sucrose concentration was 10–25%. Nymphs gained more weight during the 1st 24 hr on diets containing 20–25% sucrose than on those containing lower or higher concentrations of sucrose. Similar results on weight gains were observed after 48 hr, but after 72 hr, the highest weight gain was observed on diets containing 35% sucrose. Aphids on 0–30% sucrose diets did not become adults whereas those on 35% sucrose diets were reared continuously for several generations. Generally similar results were obtained when 1st-stage nymphs were fed on a 30% sucrose diet for 20 hr prior to their transfer to diets containing different concentrations of sucrose, with the main difference that such nymphs ingested relatively larger amounts of the sucrosefree diet. However, after 24 hr of feeding, aphids lost weight on the 0 and 5% sucrose diets, suggesting that at least 10% sucrose was necessary for normal absorption. Aphids reproduced mainly on the 10, 15, and 35% sucrose diets, and the highest number of progeny was produced on the latter diet, where aphids were reared for several generations. It is suggested that the better performance of A. pisum on diets containing 35% sucrose was caused by some contaminant (possibly a heavy metal) present in sucrose and essential for aphid growth and reproduction, which was provided in near optimum amounts only when the sucrose concentration was at 35%, and was not necessarily a result of high concentration of sucrose itself.