Despite the usefulness of nematicidal compounds in agricultural practices, but it cause environmentally problems, which lead to seek about safe and alternative agents as tools to be used in the plant nematodes management programs. Abamectin is one of the suggested alternative biorational tool that belongs to avermectin group, which belong to macro cyclic lactones metabolites produced by a natural fermentation of the bacterium Streptomyces avermitilis. Abamectin mixture contains more than 80% avermectin B1 a and less than 20% avermectin B1 b. Meanwhile, abamectin used as an insecticide, acaricide and nematicide on vegetables, fruits and field crops. On the other hand, neem oil is a vegetable oil pressed from the fruits and seeds of the neem tree, Azadirachta indica. The neem tree was recognized for its unique properties against insects, and in improving human health. It is grown in most tropical and subtropical areas. Its leaves, bark, and seed kernels extracts, or cake, can be utilized in phytonematodes management. Various components such as nimbin, nimbidin, azadirachtin, salannin, thionemon, and meliantriol occur in the seeds, leaves, and the bark of neem with high concentrations. The effect of neem against plant parasitic nematodes was noticed and recorded in many reports, as well as its insecticidal, fungicidal and bactericidal efficacy.
Khalil M.S., Badawy M.E.I. (2012): Nematicidal activity of a biopolymer chitosan at different molecular weights against root-knot nematode, Meloidogyne incognita. Plant Protect. Sci., 48: 170-178.The nematicidal activity of four molecular weights (2.27 × 10 5 , 3.60 × 10 5 , 5.97 × 10 5 , and 9.47 × 10 5 g/mol) of a biopolymer chitosan was assayed against the root-knot nematode, Meloidogyne incognita, in vitro and in pot experiments. In laboratory assays, the nematode mortality was significantly influenced by exposure times and chitosan molecular weight. Low molecular weight chitosan (2.27 × 10 5 g/mol) was the most effective in killing the nematode with EC 50 of 283.47 and 124.90 mg/l after 24 and 48 h of treatment, respectively. In a greenhouse bioassay, all the compounds mixed in soil at one-and five-fold concentrations of the LC 50 value significantly reduced population, egg mass, and root galling of tomato seedlings compared with the untreated control. In general, the nematicidal activity of these compounds was increased dramatically with a decrease in the molecular weight. The results suggest that the chitosan at low molecular weight may serve as a natural nematicide.
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.
For many years organophosphate pesticides considered the main option for a lot of people in many countries to manage different pests. It's more than 70 years now and OPs still use with certain purposes in gardens, fields and greenhouses as crop protection agents, or even at houses as public health agents. Thus, year after year and with the repeating usage of organophosphate agents many problems were appeared as a result to excessive use of pesticides. The adverse effects of pesticides usage represented in the effects on human health, environment, pesticides residue in crops and soil & water contaminated by these pesticides. Therefore, it was necessary to throw a light on the risks that generated by irresponsible usage of organophosphate pesticides.
This work aimed to select potentially useful eco-biorational product that could be used to reduce the reproduction of root-knot nematode. The experiment was carried out in pots under net house. The results revealed that the bio-product Dipel® (Bacillus thuringiensis ) proved to be the most effective treatment that reduced the root galls and egg masses by 71.60 and 77.78%, respectively. Also, Dipel® (B. thuringiensis) Bio-nematon® (Paecilomyces lilacinus) showed their superiority between all treatments on the shoot, root length and root weight.
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