Toxicity and neurophysiological impacts of three plant-derived essential oils against the vineyard mealybug Planococcus ficus

Many natural products are able to control pests and can be used as alternatives for chemical treatments. Plant essential oils (EOs) have been found to exhibit some biological activity against many insects including mealybugs. This study aimed at studying the insecticidal activity and behavioral and neurophysiological impacts of three plant essential oils against the vine mealybug Planococcus ficus. The topical and fumigant toxicity of Cymbopogon citratus, Mentha piperita, and Pelargonium graveolens essential oils was evaluated against P. ficus adults. The chemical composition analysis of EOs by gas chromatographic-mass spectrometry (GC-MS) revealed citronellal (31.69 %), menthol (73.78 %), and geraniol (39.6%), as major components, respectively. Bioassays of EOs against vine mealybug adults through fumigation toxicity method revealed lethal concentrations LC50 values of 17.01, 26.27 and 24.52 µL·L-1 air for C. citratus, M. piperita, and P. graveolens, respectively. In both topical and fumigant bioassays, essential oil from C. citratus was the most active altering the behavioral response of treated mealybugs which becomes hyperactive and disoriented. EOs induced general stress in P. ficus adults, as evidenced by oxidative stress biomarker analyses. Biochemical analyses showed that the EOs exposure reduced the activity of acetylcholinesterase and significantly induced the glutathione S-transferases and Malondialdehydes accumulation in the vine mealybug tissues. Mortality caused by lemongrass EO positively correlated with the significant decrease in the AChE activity indicating lethal neurological effects. These toxicity bioassays and neurological impact findings provide new informations for formulating effective essential oil based-insecticides to control P. ficus in the framework of integrated pest management programs

OPTIMAL SIZING OF A HYBRID PHOTOVOLTAIC/WIND SYSTEM SUPPLYING A DESALINATION UNIT

This work presents the dimensioning of a wind-photovoltaic hybrid system for the supply of a seawater desalination plant (reverse osmosis desalination) located in Honaïne in the Tlemcen coastal region of Algeria. The plant has a production capacity of 200,000 m3 /day and supplies potable water for a population of about 555,000 people (the plant's energy demand is 1,825 MW). The main idea is to present a method for sizing and optimizing a hybrid system by introducing two scenarios: the first scenario treats the operation of the plant under good weather conditions. The second one introduces the notion of the worst month (poor weather conditions). For it, we developed a calculation code (Programming under the MATLAB environment) that allowed us to determine the size and optimization of the system, as well as the optimal technical and economic configuration (numbers of photovoltaic panels, wind turbines and batteries), as well as the total cost. The results obtained show on the one hand: the complementarity of the two scenarios, which allows a better reliability of the system, and this by using a number well defined of panels, wind turbines and batteries to ensure the long-term operation of the plant. On the other hand, the use of the hybrid system has allowed us to obtain a 51.46% benefit compared to fossil fuels, which gives the proposed study an important reliability, since it offers a very advantageous benefit in terms of cost and efficiency

Analysis of two larval-pupal parasitoids (Hymenoptera, Braconidae) in the biological control of Ceratitis capitata (Wiedemann) in Spanish Mediterranean areas

The Mediterranean fruit fly, Ceratitis capitata (Diptera: Tephritidae), is considered a key pest in fresh fruit and citrus production in the Mediterranean Bassin. Nowadays, it is being studied the use of several ecological methods against this pest in some Mediterranean countries (Spain, Morocco and Tunisia), like the Sterile Insect Technique (SIT), the classical biological control (CBC) and the search for native parasitoids. Two exotic larval-pupal parasitoids of fruit-flies have been imported by the IVIA to Spain: Diachasmimorpha tryoni and D. longicaudata. As it occurs in other countries, in Spain it is being studied the combined use of the SIT and overflooding releases of parasitoids to combat Medfiy populations. To achieve this, only one parasitoid species is usually mass reared and released. Over the last two years we have been analyzing the competitiveness of D. longicaudata and D. tryoni in order to choose the species to be used together with the SIT for the integrated control of the Medfl

Host plant range of a fruit fly community (Diptera: Tephritidae): Does fruit composition influence larval performance?

Background: Phytophagous insects differ in their degree of specialisation on host plants, and range from strictly monophagous species that can develop on only one host plant to extremely polyphagous species that can develop on hundreds of plant species in many families. Nutritional compounds in host fruits affect several larval traits that may be related to adult fitness. In this study, we determined the relationship between fruit nutrient composition and the degree of host specialisation of seven of the eight tephritid species present in La Réunion; these species are known to have very different host ranges in natura. In the laboratory, larval survival, larval developmental time, and pupal weight were assessed on 22 fruit species occurring in La Réunion. In addition, data on fruit nutritional composition were obtained from existing databases. Results: For each tephritid, the three larval traits were significantly affected by fruit species and the effects of fruits on larval traits differed among tephritids. As expected, the polyphagous species Bactrocera zonata, Ceratitis catoirii, C. rosa, and C. capitata were able to survive on a larger range of fruits than the oligophagous species Zeugodacus cucurbitae, Dacus demmerezi, and Neoceratitis cyanescens. Pupal weight was positively correlated with larval survival and was negatively correlated with developmental time for polyphagous species. Canonical correspondence analysis of the relationship between fruit nutrient composition and tephritid survival showed that polyphagous species survived better than oligophagous ones in fruits containing higher concentrations of carbohydrate, fibre, and lipid. Conclusion: Nutrient composition of host fruit at least partly explains the suitability of host fruits for larvae. Completed with female preferences experiments these results will increase our understanding of factors affecting tephritid host range. (Résumé d'auteur

Utilisation des pailles de céréales traitées à l'ammoniac et à l'urée par différentes espèces de ruminants dans les pays d'Afrique du Nord

Doctorat en sciences agronomiques -- UCL, 199

Traitement de la paille de blé à l'ammoniac et à l'urée : effet sur la digestibilité ruminale et sur le comportement alimentaire et mérycique chez les bovins

International audienc

Introduction et acclimatation en Tunisie d'Eretmocerus debachi Rose Rosen (Hym., Aphelinidae) parasitoïde de Parabemisia myricae (Kuwana) (Hom., Aleurodidae)

National audienc