Fipronil and emamectin benzoate (EMB) are effective insecticides for controlling cotton leafworm, Spodoptera littoralis. Fipronil works by blocking gamma-amino butyric acid (GABA) gated chloride. In contrast, EMB is activating GABA transporters. The objectives of our study were to assess relative toxicity of the technical fipronil and EMB alone and in mixture against S. littoralis. In addition, the GABA content was simultaneously determined using HPLC. Technical fipronil and EMB and their mixtures were applied topically to the fourth-instar larvae, and their LD50 values were estimated after 48 h. Results demonstrated that the LD50 for EMB applied alone was 0.751 ng/larva which was much less than for fipronil 7.271 ng/larva. Each of the two insecticides alone showed a significant decrease in GABA content at LD10, LD25, and LD50 doses, while their mixtures induced GABA levels. The highest potentiation was observed when both insecticides were in a mixture at the ratio of LD10:LD10 which was associated with higher increase in GABA levels. Moreover, the weight of the alive larvae was less than that was in the untreated control. However, all mixtures exhibited potentiation effect, except for the mixture of fipronil at LD50 with EMB at LD10, LD25, and LD50 that had antagonistic effect correlated with the lowest decrease in GABA level. Results suggested that lower doses of both insecticides in a binary mixture had potentiation effect against S. littoralis. This mixture could be used in combination as field application for successful and effective control of S. littoralis and would also help in managing insecticide resistance.

Loose smut of wheat caused by Ustilago tritici is a disease of economic important in Egypt. It is an exclusively seedborne disease and can be controlled by applying pre-sowing dry seed treatment with any of the nature products as black seed oil and cumin oil or gamma rays@ 150, 200, 250 Gy or four systemic fungicides as Premis ® 25% FS, Sumi-8 ® 2%WP, Dividend Extreme ® 11.5% FS and Raxil ® 2% DS. The present study was carried out during 2016/2017 and 2017/2018 growing seasons and aimed to evolve an efficient method of application of fungicides, nature products and radiation for an economic control of loose smut of wheat and also evaluated for the determination of four azole fungicides residues in wheat and soil samples. The tested fungicides were highly effective in controlling the disease and gave more than 98% disease control with high grain yield while nature products as black seed oil and cumin oil gave 61.2% and 56.6% control, respectively. For determining the fungicides residues, the fungicides were extracted and cleaned using the 'Quick Easy Cheap Effective Rugged and Safe' (QuEChERS) method and followed by gas chromatographs coupled to electron capture (µECD) detector analysis. The analytical method was evaluated in terms of recoveries, repeatability, limit of quantitation (LOQ) and matrix effects. The recoveries were between 80.12 to 97.85% with relative standard deviation (RSDs) ranged between 6.12-10.65%. Limit of detections ranged from 0.002 to 0.01mg/kg. LOQ for tested fungicides less than or met the maximum residue limits (MRL).