Bulletin of Insectology 55 (1-2): 35-37 The effects of 20-hydroxyecdysone, metyrapone and dithiodiglucose on survival and reproduction of the aphid,

The effects of systemically applied metyrapone, 20-hydroxyecdysone and dithiodiglucose on reproduction, development and survival were followed in the aphid Myzus persicae (Sulz.). These substances were applied as water solutions, which penetrated through the leaf stem. Most dramatic changes in aphid performance occurred at the second half of the experimental period, i.e. between days 6-12, when a noxious effect was manifested even in the controls. Metyrapone showed the most deleterious effect on survival and reproduction. This substance also caused necrotization of tobacco leaves. Dithiodiglucose and 20-hydroxyecdysone in concentration 1 mg/ml protected somehow the leaves from necrosis compelled by aphid sucking. The reproduction index and num-ber of survivals was lower than in the control test. The higher concentration (2 mg/ml) rapidly decreased reproduction and survival rate, and dramatically increased mortality, particularly in the case of dithiodiglucose, when the trial had to be stopped after 6th days