No abstract

Drosophila suzukii causes considerable economic damage to small and thin-skinned fruits including cherry, blueberry, raspberry, grape and strawberry. Since it attacks fruits at the ripening stage, the use of chemical pesticides is limited due to the high risk of residues on fruit. Biological control is thus expected to play an essential role in managing this pest. The Gram-negative bacterium, Photorhabdus luminescens and its symbiotic Heterorhabditis spp. nematode have been shown to be highly pathogenic to insects, with a potential for replacing pesticides to suppress several pests. Insecticidal activity of P. luminescens at different bacterial cell concentrations and its cell-free supernatant were assessed against third-instar larvae and pupae of D. suzukii under laboratory conditions. P. luminescens suspensions had a significant oral and contact toxicity on D. suzukii larvae and pupae, with mortalities up to of 70–100% 10 days after treatment. Cell-free supernatant in the diet also doubled mortality rates of feeding larvae. Our results suggest that P. luminescens may be a promising candidate for biological control of D. suzukii, and its use in integrated pest management (IPM) programs is discussed.

No abstract

The sustainability of agroecosystems are maintained with agro-chemicals. However, after more than 80 years of intensive use, many pests and pathogens have developed resistance to the currently used chemistries. Thus, we explored the isolation and bioactivity of a chemical compound, Precocene I, isolated from the perennial grass, Desmosstachya bipinnata (L.) Stapf. Fractions produced from chloroform extractions showed suppressive activity on larvae of Spodoptera litura (Lepidoptera: Noctuidae), the Oriental armyworm. Column chromatography analyses identified Precocene I confirmed using FTIR, HPLC and NMR techniques. The bioactivity of the plant-extracted Dp-Precocene I was compared to a commercially produced Precocene I standard. The percentage of mortality observed in insects fed on plant tissue treated with 60 ppm Db-Precocene I was 97, 87 and 81, respectively, for the second, third and fourth instar larvae. The LC50 value of third instars was 23.2 ppm. The percentages of survival, pupation, fecundity and egg hatch were altered at sub-lethal concentrations of Db-Precocene I (2, 4, 6 and 8 ppm, sprays on castor leaves). The observed effects were negatively correlated with concentration, with a decrease in effects as concentrations increased. Distinct changes in feeding activity and damage to gut tissues were observed upon histological examination of S. litura larvae after the ingestion of Db-Precocene I treatments. Comparative analyses of mortality on a non-target organism, the earthworm, Eisenia fetida, at equal concentrations of Precocene I and two chemical pesticides (cypermethrin and monocrotophos) produced mortality only with the chemical pesticide treatments. These results of Db-Precocene I as a highly active bioactive compound support further research to develop production from the grass D. bipinnata as an affordable resource for Precocene-I-based insecticides.

Even though the green revolution was a significant turning point in agriculture, it was also marked by the widespread use of chemical pesticides, which prompted severe concerns about their influence on human and environmental health. As a result, the demand for healthier and more environmentally friendly alternatives to control plant diseases and avoid food spoilage is intensifying. Among the proposed alternatives, food by-product extracts, especially from the most consumed fruits in Egypt, eggplant, sugar apple, and pomegranate peel wastes, were largely ignored. Hence, we chose them to evaluate their antifungal and antiaflatoxigenic activities against maize fungus, Aspergillus flavus. All the extracts exhibited multiple degrees of antifungal growth and aflatoxin B1 (AFB1) inhibitory activities (35.52% to 91.18%) in broth media. Additionally, diethyl ether 50% eggplant, ethanol 75% sugar apple, and diethyl ether 25% pomegranate extracts exhibited the highest AFB1 inhibition, of 96.11%, 94.85%, and 78.83%, respectively, after one month of treated-maize storage. At the same time, Topsin fungicide demonstrated an AFB1 inhibition ratio of 72.95%. The relative transcriptional levels of three structural and two regulatory genes, aflD, aflP, aflQ, aflR, and aflS, were downregulated compared to the infected control. The phenolic content (116.88 mg GAEs/g DW) was highest in the 25% diethyl ether pomegranate peel extract, while the antioxidant activity was highest in the 75% ethanol sugar apple extract (94.02 µg/mL). The most abundant active compounds were found in the GC-MS analysis of the fruit peel extracts: α-kaurene, α-fenchene, p-allylphenol, octadecanoic acid, 3,5-dihydroxy phenol, hexestrol, xanthinin, and linoleic acid. Finally, the three fruit peel waste extracts could be a prospective source of friendly ecological compounds that act as environmentally safer and more protective alternatives to inhibit AFB1 production in maize storage.

The rice weevil, Sitophilus oryzae (L.), and the red flour beetle, Tribolium castaneum (Herbst), are key stored-product pests in Egypt and worldwide. The extensive use of synthetic insecticides has led to adverse effects on the environment, human health, and pest resistance. As a result, environmentally friendly pest management alternatives are desperately required. The botanical oils of jojoba, Simmondsia chinensis (L.), and rosemary, Rosmarinus officinalis L. plants growing in Egypt were extracted, identified by gas chromatography/mass spectrometry (GC–MS), and evaluated for their insecticidal activity against S. oryzae and T. castaneum. The main constituents identified in BOs were carvyl acetate (20.73%) and retinol (16.75%) for S. chinensis and camphor (15.57%), coumarin (15.19%), verbenone (14.82%), and 1,8-cineole (6.76%) for R. officinalis. The S. chinensis and R. officinalis BOs caused significant contact toxicities against S. oryzae and T. castaneum adults, providing LC50 values of 24.37, 68.47, and 11.58, 141.8 ppm at 3 days after treatment (DAT), respectively. S. chinensis oil exhibited significant fumigation toxicity against both insects; however, it was more effective against S. oryzae (LC50 = 29.52 ppm/L air) than against T. castaneum (LC50 = 113.47 ppm/L air) at 3 DAT. Although the essential oil (EO) of R. officinalis significantly showed fumigation toxicity for S. oryzae (LC50 = 256.1 and 0.028 ppm/L air at 1 and 3 DAT, respectively), it was not effective against T. castaneum. These BOs could be beneficial for establishing IPM programs for suppressing S. oryzae and T. castaneum.

In this study, the potential of some bio-agents, fluopyram and fosthiazate were investigated against rootknot nematodes (Meloidogyne spp.) on guava trees under field conditions for two successive seasons (2020 & 2021). The examined bio-agents were; Bio-Nematon ® (Paecilomyces lilacinus), Bio Cure-F ® (Trichoderma viridi), Bio Cure-B ® (Pseudomonas fluorescens) and BIOTECT ® (Bacillus thuringiensis var. kurstaki). The infection parameters of root-knot nematodes (Meloidogyne spp.) were recorded at 35 and 70 days after treatment. Resultsindicated that all the applied treatments suppressed the soil population density (J2/250g soil) at range of 68.75 to 88.85% during the 1 st season, and from 57.72 to 92.92% during the 2 nd season. Besides, the numbers of root galls were decreased at range of 60.22 to 77.11% and from 57.90 to 70.90% during 1 st and 2 nd seasons, respectively. Also, the number of isolated eggs from roots was decreased at range of 67.13 to 94.61% and from 51.37 to 88.45% during 1 st and 2 nd seasons, respectively. However, the content of total N, P and K (%) in leaves of guava trees was fluctuated during both seasons.

The encapsulation of pesticides within nanoparticles is a promising approach of advanced technology in sustainable agriculture. Lambda-cyhalothrin (LC) was encapsulated by the ionotropic gelation technique into chitosan (CS)/tripolyphosphate (TPP) and CS/alginate (ALG) matrixes. CS-LC nanoparticles were characterized, and their efficacy was then evaluated against the key pest of soft fruits in Europe and the United States, Drosophila suzukii. The encapsulation efficiency (74%), nanoparticle yield (80%), polydispersity index (0.341), zeta potential (−23.1 mV) and particle size (278 nm) were determined at the optimum conditions. FTIR confirmed the cross-linkage between CS and TPP/ALG in the nanoparticles. The optimum formula recommended by the fractional factorial design was associated with the formulation variables of CS of high or low molecular weight, cross-linking agent (TPP), LC concentration (1.5% w/v) and stirring rate (1500 rpm), showing the highest desirability value (0.5511). CS-LC nanoparticles of the lowest particle size (278 nm) exhibited the highest percent mortality of D. suzukii males (86%) and females (84%), exceeding that caused by the commercial product (Karate-zeon® 10% CS) at 2 HAT. This is the first work to use the ionic gelation technique to make LC nanoparticles, to the best of our knowledge. The encapsulation of chemical pesticides within biodegradable polymeric nanoparticles could be helpful for establishing a sustainable IPM strategy with benefits for human and environmental health and the lifetime of pesticides.