Toxicity of the active fraction of Pergularia tomentosa and the aggregation pheromone phenylacetonitrile on Schistocerca gregaria fourth-instar nymph: effects on behavior and acetylcholinesterase activity

Chemical insecticides remain the most used approach in locust control although they present a serious menace to human health and the environment. The search for alternative control methods, efficient and environmentally friendly, has become indispensable. The aim of this work is to study the effect of the aggregation pheromone, phenylacetonitrile, alone or in combination with the active fraction of Pergularia tomentosa on Schistocerca gregaria fourth-instar nymph. Toxicity bioassays showed that the combination of phenylacetonitrile with the active fraction of P. tomentosa significantly increased nymph mortality. Results also showed that the aggregation pheromone caused significant mortality especially after 6 hours of exposure. The pheromone also caused neurotoxic effects on S. gregaria nymph due to the disturbance of the acetylcholinesterase activity. We also noted the presence of cannibalism phenomenon. Phenylacetonitrile seems to have an effect on phase ployphenism of S. gregaria imagos that exhibit specific traits to the solitarious phase

AGRO-MORPHOLOGICAL RESPONSE OF CORN (Zea mays L.) TO A BIOSTIMULANT FROM THE SOUTHEASTERN ALGERIA

Abstract: This study highlights the effect of a biostimulant based on Trichoderma, indigenous antagonistic fungus from the region of Touggourt, on the development of a local variety of corn. This study was conducted at the experimental station of National Institute of Agronomic Research (Sidi Mehdi, Touggourt) as a complete randomaize block designe. The examined agro-morphological parameters showed that the application of this bioproduct stimulates vegetative growth of the plant. Besides, better germination and earliness of seeds. The results showed more interesting values were obtained in the treated plots (height = 135.9 cm, diameter = 28.9 mm, surface of leaves = 318 cm2, Pan = 10.2 panicles/plant) compared to those of the controls (height = 98.6 cm, diameter = 23.7 mm, surface of leaves = 260.4 cm², Pan = 7.4 panicles/plant). Statistical analyzes confirmed the existence of a very highly significant difference between treated and control subjects

DIFFERENCE IN CUTICLE COMPONENT AND IMMUNOCOMPETENCE IN NURSE AND FORAGER WORKER HONEYBEE (APIS MELLIFERA L)

The aim of this work is to study the difference of physiology between the workerbee nurse and forager (Apis mellifera intermissa). The chosen physiologicalcharacteristics were the component of the cuticle (protein-chitin content) and themeasure of the efficiency of immune system (the total number of haemocytes(THC), the normal haemocytes and the relative mass of fat body). The THC iswidely used as an indicator of cellular immunocompetence of insects. The normalhaemocytes, also referred to immunocytes, indicate the integrity of cellularimmune system. The fat body is an indirect measurement of induced humoralimmunocompetence. The THC and the normal haemocytes were determined by themethod described by Amdam et al., (2004). For the estimation of the cuticularabdominal protein-chitin content, the method described by Berghiche et al., (2007)was employed. The relative mass of fat body was determined using an etherextraction method according to Doums et al., (2002) and Wilson-Rich et al.,(2008).The results show that a considerable percentage of a cuticular protein and adecrease of chitin was observed in nurse compared to forager. The older beesexhibited a strong reduction in the immun parameters

Repellency and toxicity of the crude ethanolic extract of Limoniastrum guyonianum against Tribolium castaneum. Acheuk, F., Belaid, M., Lakhdari, W., Abdellaoui, K., Dehliz, A., and Mokrane, K. (Algeria/Tunisia)

In nature, the interaction between plants and insects has led to the production of a set of secondary compounds. Many plant secondary metabolites have significant insecticidal activity. The aim of this study is to evaluate the repellent and insecticidal effect of the crude ethanolic extract of Limoniastrum guyonianum against adults of the red flour beetle Tribolium castaneum. For the insecticidal activity, five doses (100, 200, 400, 600, and 800 µg/insect) were tested and were topically applied onto insect thorax. An area preference method was adopted to assess the repellent activity. A phytochemical study and measurement of two enzymatic biomarkers: acetylcholinesterase (AChE) and gluthatione Stransferase (GST) were made to understand the mechanisms of toxic action of the tested extract. Phytochemical study showed the presence of various groups of natural products. The plant is rich in flavonoids, tannins, alkaloids, and glycosides. Low amount of saponins was noted. The study also showed that this plant does not contain iridoids. For repellent activity, the results showed that the highest dose (800 µg/insect) exhibited obvious repellent effect against T. castaneum. The repellency percentage was 90.14 ± 2.5% after 4 h of exposure. The crude extract was found to be toxic to T. castaneum and the corresponding LD50value was 218.3 μg/insect. Moreover, the extract inhibits the activity of the acetylcholinesterase (IC50: 205.7 µg/insect)

Effects of Latex from Pergularia tomentosa and the Aggregation Pheromone, Phenylacetonitrile, on Locusta migratoria Larvae

Despite being a serious risk to human health and environment, chemical insecticides remain the most used for locust control. Searching for alternative control methods, effective and compatible with the environment, has become of increasing interest. Plant latex is an endogenous fluid secreted from highly specialized laticifer cells and has been suggested to act as a plant defense system. The aim of the present investigation was to study the insecticidal potentialities of Pergularia tomentosa latex at different concentrations, alone or in combination with the penylacetonitrile (PAN), on the 4th instar larvae of Locusta migratoria. The obtained results showed that the latex revealed an interesting insecticidal activity against L. migratoria larvae, resulting in a mortality reaching 96.49 %, 6 days after treatment. Toxicity bioassays revealed that PAN, associated with the latex, is able to accelerate and to increase the mortality rate. Pheromone-based treatment affected the health of treated insects by significantly reducing their respiratory rhythms. PAN was shown able to alter, quantitatively and qualitatively, the larval blood cells as expressed by the significant decrease in the number of the differential haemocyte counts (prohemocyte, plasmatocytes and granulocytes) and the important cell lysis

Antifeedant and antigonadotropic effects of Ruta chalepensis methanolic extract against Locusta migratoria. Abdellaoui, K., Miladi, M., Ben Marzouk, I., Bahloul, N., Acheuk, F., Chaira, N., and Ben Halima-Kamel, M. (Tunisia / Algeria)

The migratory locust Locusta migratoria is one of the most important pests due to its extensive and serious damage to crops in large parts of Africa and Asia. To identify novel new environment friendly products for the management of the migratory locust, experiments were conducted to assess the effect of a methanolic extract of Ruta chalepensis (ME-Rc) on feeding activity and different reproductive phases of L. migratoria. The results showed that ME-Rc caused a significant decline in food intake and insect digestibility. The treatment applied to adult females caused a significant lengthening of the preoviposition period and a significant reduction in both fecundity and fertility. ME-Rc also affected growth and development of oocytes as evidenced by measurements of ovarian weight, length and volume of terminal oocytes and ovarian index. In addition, ME-Rc based-treatments led to disturbances in the incorporation of haemolymph metabolites (proteins and carbohydrates) in oocytes resulting in a significant decrease in their concentrations in ovaries

Status and Prospects of Botanical Biopesticides in Europe and Mediterranean Countries

Concerning human and environmental health, safe alternatives to synthetic pesticides are urgently needed. Many of the currently used synthetic pesticides are not authorized for application in organic agriculture. In addition, the developed resistances of various pests against classical pesticides necessitate the urgent demand for efficient and safe products with novel modes of action. Botanical pesticides are assumed to be effective against various crop pests, and they are easily biodegradable and available in high quantities and at a reasonable cost. Many of them may act by diverse yet unexplored mechanisms of action. It is therefore surprising that only few plant species have been developed for commercial usage as biopesticides. This article reviews the status of botanical pesticides, especially in Europe and Mediterranean countries, deepening their active principles and mechanisms of action. Moreover, some constraints and challenges in the development of novel biopesticides are highlighted