Efficacy of chemical and bio-pesticides on cowpea aphid, Aphis craccivora, and their residues on the productivity of fennel plants (Foeniculum vulgare)

The residual of pesticides after applications and their effects on plant parameters are very important to be estimated. Therefore, this study investigated the efficacy of six insecticides (acetamiprid, thiamethoxam, imidacloprid, azadirachtin, thiocyclam, and sulfoxaflor) against Aphis craccivora adults and their residue in fennel plants (Foeniculum vulgare) in two successive seasons. The physiological and phytochemical responses of fennel plants after exposure to these insecticides were studied. The tested insecticides were able to keep the reduction percentage of A. craccivora adults above 90% except of azadirachtin, which reached 52% only. Thiocyclam and sulfoxaflor were more effective in decreasing the number of A. craccivora adults than other treatments until 7th day after application. Significant effects were observed among different treatments compared to control for all the vegetative parameters of fennel plants. In the first season, the highest plant height (151.83 cm) and number of umbel/plant (77.63) were obtained in plants treated with thiocyclam with the values from fruit yield (2504 kg/fed) followed by azadirachtin (2281 kg/fed). The same trend for these parameters was obtained in the 2nd season. Azadirachtin demonstrated the best value of oil yield (2.99 and 3.77 ml/plant) for 2017 and 2018 seasons, respectively). The main chemical compound of fennel seed essential oils was estragole (methyl chavicol) and ranged from 68.10 (with Azadirachtin) to 79.90% (with control), the undesirable component, with increasing the amount of anethole (10.06%). It can be concluded that, thiocyclam, sulfoxaflor with neonicotinoid group could be included as a useful agent in a comprehensive aphid management programs in Egypt.