L’azadirachtine, un pesticide naturel aux effets multiples

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Analyse des hydrocarbures cuticulaires chez Blattella germanica : effets de divers groupes de pesticides

Analyse des hydrocarbures cuticulaires chez [i]Blattella germanica[/i] : effets de divers groupes de pesticides. Actes de la CIFE VI. Série Zoologi

Boric acid toxicity to the German cockroach, Blattella germanica: Alterations in midgut structure, and acetylcholinesterase and glutathione S-transferase activity

0048-3575 doi: DOI: 10.1016/j.pestbp.2005.05.002Oral toxicity of boric acid, an inorganic insecticide, was evaluated on German cockroach, Blattella germanica L. (Dictyoptera, Blattellidae). Newly emerged adults were exposed to various concentrations of boric acid incorporated into the diet. Results showed that treated insects exhibited toxic symptoms with a dose-dependent mortality. Histological study of midgut revealed alterations in the epithelial cells and a signiWcant increase in the epithelium thickness. In a second series of experiments, the compound was investigated on the activities of acetylcholinesterase (AChE) and glutathione S-transferases (GSTs). Data showed that the compound induced GSTs and reduced the activity of AChE. From this experiment, it may be concluded that ingested boric acid caused death of insects perhaps ultimately by starvation via alterations of the midgut. Additionally, the compound seemed to present a neurotoxic action as evidenced by the symptoms of poisoning and the reduction in AchE activity

Halofenozide affects sexual behavior, cuticular hydrocarbons and reproduction in the female German cockroach Blattella germanica (Dictyoptera, Blattellidae)

Halofenozide, a dibenzoylhydrazine insect growth regulator, was applied topically to female individuals of the most prevalent German cockroach species, Blattella germanica, and its effects on sexual behaviour, cuticular hydrocarbons and reproduction were investigated. Dissection of treated females showed clearly reduced numbers of oocytes and volume of basal oocytes. Interestingly, the ecdysteroid amounts were also significantly lower. Characterization of the cuticular hydrocarbons by gas chromatography showed 13 major compounds, including the female contact sex pheromone precursor. It was clear that halofenozide application resulted in significantly lower amounts of all the investigated cuticular components. Finally, behavioural tests revealed that halofenozide treatment of females caused a significant decrease in sexual receptivity of the untreated conspecific males. Thus, exposure to the ecdysteroid agonist can negatively affect the male's response to a calling female, which is linked with and most likely caused by lesser production of female contact sex pheromone and a delay in the up-regulation of ecdysteroid amounts, and in turn this provoked an obvious lower oocyte number and basal oocyte size as measures of reproduction

Toxicity of boric acid to Blattella germanica (Dictyoptera: Blattellidae) and analysis of residues in several organs

1373-7503 (Print) Journal ArticlePestiferous cockroach species are associated closely with humans and are important from medical and public health points of view. Conventional insecticides have been used widely to control cockroaches which have developed resistance to these compounds. Thus, interest has again centered on lesser-used compounds such as boric acid. Boric acid has been used as an insecticide for many years, especially against cockroach. Its mode of action on insects has not been satisfactorily established. In Algeria, Blattella germanica (Dictyoptera: Blattellidae) is a serious pest in the urban environment and their infestation were controlled for many years by organophosphate, carbamate or pyrethroid insecticides. In order to obtain more information on the mode of action of boric acid, we first evaluated the oral toxicity of boric acid on B. germanica adults. Then, the compound was determined in several organs by an colorimetric method. This insecticide was incorporated into the diet and orally administered at different concentrations ranging from 1 to 40% (w/w) to newly emerged adults. Mortality was recorded at different times during treatment (24, 48, 72 and 144 h). Treatment resulted in a dose-dependent mortality since the LD50 (%) recorded are 85 at 24 h, 67 at 48 h, 39 at 72 h and 8 at 144 h, respectively. Then the quantity of boric acid accumulated in several organs (hemolymph, gut, ovaries, testicles and fat body) was determined as function the duration of treatment (1 to 5 days) for two doses (LD50 and LD90). Results revealed that bioaccumulation of residues in these organs increased as function the duration of treatment. In addition, relatively important amounts of residues, are detected in fat body

Cuticular hydrocarbon profiles in Blattella germanica: effects of halofenozide, boric acid and benfuracarb

1379-1176 (Print) Journal ArticleIn order to complete previous studies conducted on Blattella germanica, three insecticides from different groups were evaluated: boric acid, an inorganic compound, benfuracarb, a carbamate, and halofenozide, a non-steroidal ecdysone agonist. Boric acid (8.20%, LD50) and benfuracarb (2%, LD50) were incorporated into the diet and orally administrated to newly emerged adults of both sexes, while halofenozide (0.33%, LD50) was applied topically. Hydrocarbons extracts was made on bidistilled pentane from control and treated series sampled 6 days following treatment. Extracts was analyzed by gas chromatography. Data showed that cuticular profiles of control and treated series were qualitatively similar with thirteen major compounds; however, significant quantitative differences were noted. Boric acid seemed to feminize the cuticular profile in males with a significant reduction of the two first cuticular compounds detected. Halofenozide and benfuracarb reduced cuticular compounds in both sexes

Sublethal effects on reproduction and biomarkers by spinosad and indoxacarb in cockroaches Blattella germanica

The present project investigated effects of two insecticides, the naturalyte spinosad and the oxadiazine indoxacarb, against adults of the cosmopolitan pest insect Blanella germanica (L.). At 6 days after topical treatment on newly moulted adults, the median lethal dose (LD50) was 429 ng/insect for spinosad and 51 ng/insect for indoxacarb, indicating that indoxacarb was more active than spinosad. Both treatments showed a cessation of feeding, followed by paralysis and death. In continuation, surviving adults showed a reduced reproduction with a significant reduction in numbers of oocytes, in basal oocyte volume, and in numbers of laid and hatched eggs per ootheca. In parallel, we determined the biomarkers acetylcholinesterase (AChE), lactate deshydrogenase (LDH), glutathione S-transferase (GST) and glutathione (GSH) upon treatment. For both spinosad and indoxacarb, AChE and GSH were reduced, while LDH and GST were increased. The data are discussed in relation to insecticide use, sublethal effects, chemical stress and metabolism

Reproductive effects in German cockroaches by ecdysteroid agonist RH-0345, juvenile hormone analogue methoprene and carbamate benfuracarb

1379-1176 (Print) Journal Article Research Support, Non-U.S. Gov'tBlatta germanica is the more prevalent cockroach species in Algeria. In the present study, we tested the effect on reproduction in B. germanica of two insect growth regulators, RH-0345, a benzoylhydrazine analogue that mimics the action of 20-hydroxyecdysone, and methoprene, one of the most commercially important juvenile hormone analogues, and a novel carbamate insecticide, benfuracarb. The compounds were applied topically (10 and 20 microg/insect for RH-0345, and 1 and 10 microg/insect for methoprene) or orally administrated (at 2% for benfuracarb) on newly emerged females and evaluated on reproductive events during the adult life (2, 4 and 6 days). Treatment with RH-0345 and benfuracarb reduced significantly the number of oocytes, the size and the volume of the basal oocyte during the experimental period. Methoprene distorted the ovarian development since it caused a significant reduction in the number of oocytes at 2, 4 and 6 days for the two tested doses, and an increase in oocyte size at 2, 4 and 6 days with 1 microg and a decrease with 10 microg. In a second series of experiments, the effects of these compounds were assayed on the ovarian proteins. Data from biochemical analysis revealed that RH-0345 and benfuracarb reduced the ovarian amounts of proteins, while treatment with methoprene increased it during the sexual maturation