Summary Avermectins and spinosyns are structurally related natural products of microbial origin and belong to a new family of macrolides which are active against a vast array of invertebrate pests. In the present study, the effects of four members of macrolides; abamectin (ABM), emamectin benzoate (EMB), spinosad (SPI) and spinetoram (SPIT), on Meloidogyne incognita were investigated under in vitro and in vivo conditions. All compounds reduced egg hatching and led to high mortality of the nematode second-stage juveniles (J2). ABM showed the maximum rate of egg hatching inhibition and J2 mortality while SPIT recorded the minimum. All treatments reduced the number of galls, egg masses, eggs/egg mass in roots and J2 in the soil when compared to the control. Based on the 10 folds of the 24 h-LC50 values of J2 mortality in vitro, EMB and ABM exhibited higher percent reduction in galls (79.68 and 71.45%), egg masses (75.19 and 70.54%), eggs/egg mass (60.49 and 40.91%) and J2 in the soil (90.31 and 86.54%), respectively, compared to SPI and SPIT. Significant increase in tomato shoot height occurred in all biopesticides (10 folds) and SPIT (20 folds). SPI at 10 folds of the 24 h-LC50 values of J2 mortality in vitro, significantly increased root length while ABM at 50 folds and SPIT at 20 folds decreased root length by 5.15% and 5.88%, respectively, compared to the untreated inoculated plants. In all treatments, the dry shoot and root weights increased, compared to the untreated control. Our findings suggest that these macrolides have the ability to regulate nematode population densities and may be an alternative to classical nematicides.

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The present study was conducted to determine the effect of baits containing nano particles of silica against the fourth instar larvae of Agrotis ipsilon (Hufn.) along sequential daily intervals post treatment under laboratory conditions. The determined percentages of larval mortality due to the admixed baits with SiNPs increased up to 100% after 15 days of application. The admixing of nanoparticles of silica in the bait during the sensitive period of larval development caused morphological abnormalities that are generally irreversible and often lead to death, beside certain biochemical changes of some inorganic elements in the haemolymph of the treated insects. It could be concluded that the tested nanoparticles of silica were most effective and indicated the highest concentration reductions of inorganic constituents in larval haemolymph, especially calcium, sodium and potassium. Therefore, more attention must be directed towards the inorganic constituents in the larval haemolymph as biomarkers for SiNPs efficacy.

Laboratory studies were conducted to evaluate the pathogenic effect of Dipel Bacillus thuringiensis separately, and in combination with sugar on the fourth instar larvae of spiny bollworm using both a dipping and a residue film method of application. In addition the histopathological changes in the treated mid-gut larvae are described.