Guava is a nutritious fruit that has perishable behavior during storage. We aimed to determine the influences of some edible coatings (namely, cactus pear stem (10%), moringa (10%), and henna leaf (3%) extracts incorporated with gum Arabic (10%)), on the guava fruits’ properties when stored under ambient and refrigeration temperatures for 7, 14, and 21 days. The results revealed that the coating with gum Arabic (10%) only, or combined with the natural plant extracts, exhibited a significant reduction in weight loss, decay, and rot ratio. Meanwhile, there were notable increases in marketability. Moreover, among all tested treatments, the application of gum Arabic (10%) + moringa extract (10%) was the superior treatment for most studied parameters, and exhibited for the highest values for maintaining firmness, total soluble solids, total sugars, and total antioxidant activity. Overall, it was suggested that coating guava with 10% gum Arabic combined with other plant extracts could maintain the postharvest storage quality of the cold-storage guava.
The risk level of several insecticides of various chemical classes was estimated for honeybee workers, Apis mellifera L. (Hymenoptera: Apidae). Lethal time calculation was used to risk assessment for honeybees. Bioassay tests were conducted with six insecticides [dinotefuran (neonicotinoid), methomyl (carbamate), profenofos (organophosphate), azadirachtin (botanicalbioinsecticide), spinosad (bioinsecticide-an extract of the fermentation broth of soil actinomycete) and chlorfluazuron (IGR)] on honeybee workers by the insecticide / food mixture technique, at seven concentrations as ratios of recommended field rate [F (ug a. i. mL-1)], for 15 days. Results revealed that dinotefuran was significantly the most toxic to bees, which gave the shortest median lethal times (LT 50s), 4.4, 4.9, 5.8, 6.4 and 10.3 days at concentrations of 1F×10-2 , 5F×10-3 , 1F×10-3 , 5F×10-4 and 1F×10-4 , respectively. Moreover, it gave 100% bee mortality after one day exposure time, at two higher concentrations, (1F×10-1) and (5F×10-2). The toxicity order of the tested insecticides for honey bees (Based on LT 95s) varied by the reducing in their concentrations, whereas it was: dinotefuran > methomyl > profenofos > azadirachtin > chlorfluazuron > spinosad, at the higher concentrations and this became azadirachtin > dinotefuran > profenofos > chlorfluazuron > methomyl > spinosad at the lowest concentrations. It was concluded that the
This study aimed to investigate the toxicity of citronella, mustard, and sage essential oils in comparison to their nanoemulsions. Laboratory bioassays were conducted against the 2 nd and 4 th instar larvae of Spodoptera littoralis. The results indicated that the LC 50 values were 0.231, 1.898 and 2.500% for bulk oils of mustard, citronella, and sage against 2 nd instar larvae of S. littoralis, respectively, while they were 0.253, 0.266, and 0.962% for their nanoemulsions, respectively. The LC 50 values were 0.889, 3.358 and 0.995% for bulk oils of mustard, citronella, and sage against the fourth instar larvae, respectively, while the LC 50 values of their nanoemulsions were 0.657, 0.572 and 0.488%, respectively. The fourth instar larvae were treated with LC 50s concentrations of tested essential oils and their nanoemulsions to estimate the biochemical changes. The results showed that there was a significant increase in stimulation of AChE activity, in the case of mustard and citronella bulk and nanoemulsions, while there were no significant changes in sage oil bulk treatment and its nanoemulsion compared with the control. Also, there was a significant decrease in activity of GST enzyme in mustard, citronella bulk oil and mustard nanoemulsion. In contrast, the activity of GST increased significantly in the treatments of sage bulk oil, mustard, citronella and nanoemulsion of sage oil. Alpha esterases activity decreased significantly in all treatments except nanoemulsion of mustard oil which caused a significant increase in the enzyme activities compared with the control.
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