Lethal and sub-lethal effects of palizin insecticide and salinity stress on Aphis gossypii in vitro

Melon aphid Aphis gossypii is one of the economic pests of melon that has a high adaptability to various environmental conditions, including salinity. In this study, the lethal and sub-lethal (LD10) effects of Palizin soap insecticide (0, 450, 696, 1078, 1669, 2583 and 4000 ppm) were investigated on A. gossypii reared on melon seedlings under salinity stress (0, 20, 40 and 60 mM) in a Factorial experiment based on completely random design in growth chamber (25 ± 1°C, %70 ± 5 RH and 16L/8D h photoperiod). Bioassay was performed based on leaf deep bioassay method. The LD50 values after 24 hours were estimated as 1378, 1036, 860 and 749 ppm for treatments, respectively. An inverse relationship was observed between the toxicity of Palizin and increase in salinity. To determine the effect of LD10 of Palizin on aphids, biological parameters of insect fertility in each salinity treatment were determined based on the age-stage, two-sex life table theory. The nymphs had longer development duration in treated aphids than aphids that grew under similar salinity conditions, but adult insects had a shorter longevity and less fecundity. The average of intrinsic rate of increase varied from 0.31 to 0.17 ♀/♀/days-1 and the average of generation time varied from 11.16 to 12.65 days between 0 and 60 mM salinity treatments. Based on the results, Palizin insecticide with salinity stress can be recommended for successful integrated management of aphid on melon under salinity stress conditions.