An Investigation of the toxicity of Primicarb and Imidacloprid insecticides in different growth stages of melon aphid, Aphis gossypii Glover

Melon aphids, Aphis gossypii Glover (Hemiptera: Aphididae) is one of the most important pests causing damages in vegetables fields and greenhouses. In this regard, pesticide application is usually considered as the most common forms of pest control. Excessive use of chemical pesticides, leads to an increase in pesticide residue in vegetables, and affects on consumer health. In this study, the sensitivity of the different nymphal instars and adult melon aphids to field recommended dose and half-dose of the insecticides imidacloprid (35% SC) and primicarb (50% WP) was surveyed by leaf dipping. The bioassay was also carried on the third instar of melon aphid. Moreover, based on LC50, the sensitivity of third instar was compared at intervals of 24, 48 and 72 hours, in both insecticides. The results showed that the toxicity of both pesticides was significantly reduced in later stages. Based on the results obtained, LC50 and LC90 of imidacloprid were 71.648 and 365.548 and for primicarb were 212.62 and 457.49 ppm, respectively. The mortality for imidacloprid was 45, 48.89 and 49.45% and for primicarb 43.89, 47.78 and 50.56%, after 24, 48 and 72 hours, respectively. The results also revealed that in both insecticides, the highest mortality were occurred after 24 hours and the passage of time (48 and 72 hours) did not result in higher mortality. According to results, the pest is well controlled by low doses of both insecticides, the issue that can also reduce harmful side effects on consumer health and the environment.