Effect of different antibiotics on the biological characteristics of pea aphid

To determine the application methods of different antibiotics in relation to the biological characteristics of green pea aphid Acyrthosiphon piusm (Harris), we sprayed different antibiotics (chlortetracycline HCl, chloraomycetin, oxytetracycline HCl, penicillin-G K salt and streptomycin sulfate) using different methods. The application methods were spraying antibiotics on aphids and plants, on aphid only, and on plants only. Biological parameters of green pea aphid were obtained, which were the days of development, average weight, weight difference, mean relative growth rate and average fecundity of larvae. The results showed that the order of effect of three application methods on the biological characteristics of green pea aphid was as follows: spraying antibiotics on aphids and plants > spraying antibiotics on plants only > spraying antibiotics on aphids only. The order of effect of five different antibiotics on the biological characteristics of green pea aphid was as follows: oxytetracycline HCl > chlortetracycline HCl > streptomycin sulfate > chloraomycetin > penicillin-GK salt. After sprayed both on aphids and plants, oxytetracycline HCl in five antibiotics most significantly influenced the growth and development of green pea aphids - nymph stage prolonged by 2.25 days, generation time prolonged by 3.70 days, weight dropped by 52.37%, weight difference dropped by 55.84%, mean daily relative growth rate dropped by 53.85% and average fecundity of larvae dropped by 79.07%. While aphid development period under chlortetracycline HCl treatment increased, it decreased under penicillin-GK salt, chloraomycetin and streptomycin sulfate. After treatment with five antibiotic, similar weight losses and aphid fecundity drops were noted. The influence of oxytetracycline HCl on aphid nymph stage, generation period and average body weight growth rate was significantly different from others treatment. Both oxytetracycline HCl and chlortetracycline HCl had a clear effect on the average weight and weight difference of aphids, but with no significant difference between the two. When five antibiotics sprayed on plant surface only, oxytetracycline HCl had the highest effect on the growth and development of green pea aphid. Nymph stage prolonged by 1.63 days, generation time prolonged by 3.38 days, weight dropped by 50.28%, weight difference dropped by 51.49%, mean daily relative growth rate dropped by 41.67% and aphid fecundity dropped by 75.45%. Chlortetracycline HCl had a lower effect than oxytetracycline HCl, which led to a longer development period of aphids. Then penicillin-GK salt, chloraomycetin and streptomycin sulfate shortened aphid development period. When five antibiotics sprayed on aphid only, oxytetracycline HCl still had the highest effect on aphid development - nymph stage prolonged by 0.34 days, weight dropped by 24.32%, mean daily relative growth rate dropped by 26.32% and aphid fecundity dropped by 44.23%. In conclusion, spraying antibiotics on both aphid and plant was the most effective application method and oxytetracycline HCl was the most effective antibiotic for pea aphid. The other antibiotics and application methods had less effect on pea aphid. The three combinations of antibiotics and application methods had obvious effects on green pea aphid growth and development, their action order was as follows: oxytetracycline HCl antibiotic sprayed on aphids and plants > oxytetracycline HCl sprayed on plants > chlortetracycline HCl sprayed on aphids. There was no significant difference among the three. Oxytetracycline HCl sprayed on aphids and plants was significantly different from the others combinations in terms of effect.