RESUMEN
Tuta absoluta (Meyrick) is one of the serious pests of tomatoes. This study was conducted to evaluate the effects of some chemical and biological insecticides on T. absoluta. The insecticides tested were diazinon, dichlorvos, chlorantraniliprole, deltamethrin, acetamiprid, imidacloprid, spinosad, abamectin, indoxacarb, Bacillus thuringiensis Berliner, Beauveria bassiana (Balsamo) Vuillemin, and Metarhizium anisopliae (Metschnikoff) Sorokin. Sublethal effects for the most effective insecticides tested, namely, abamectin, spinosad, chlorantraniliprole, and indoxacarb were assessed, and life table parameters were calculated. Chlorantraniliprole had the highest lethal effect on T. absoluta followed by spinosad, abamectin, and indoxacarb. On the other hand, imidacloprid was not considerably effective on T. absoluta eggs. Metarhizium anisopliae was 11 and 518 times more effective on the eggs and newly hatched larvae than B. bassiana and B. thuringiensis, respectively. Chlorantraniliprole, spinosad, abamectin, and indoxacarb affected life table parameters of T. absoluta significantly (α = 0.05). Spinosad had the highest sublethal effect on T. absoluta followed by abamectin, chlorantraniliprole, and indoxacarb. The results revealed that chlorantraniliprole, spinosad, abamectin, and indoxacarb had considerable lethal and sublethal effects on T. absoluta, and if they perform similarly in commercial greenhouses and fields, they would be suitable candidates to be considered in IPM programs for this pest.
Asunto(s)
Agentes de Control Biológico/farmacología , Control de Insectos , Insecticidas/farmacología , Mariposas Nocturnas/efectos de los fármacos , Control Biológico de Vectores , Animales , Bacillus thuringiensis/fisiología , Beauveria/fisiología , Larva/efectos de los fármacos , Larva/crecimiento & desarrollo , Tablas de Vida , Metarhizium/fisiología , Mariposas Nocturnas/crecimiento & desarrollo , Óvulo/efectos de los fármacos , Óvulo/crecimiento & desarrolloRESUMEN
Eurygaster integriceps Puton (Hemiptera: Scutelleridae) is the most serious insect pest of wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) in Iran. In this study, spatio-temporal distribution of this pest was determined in wheat by using spatial analysis by distance indices (SADIE) and geostatistics. Global positioning and geographic information systems were used for spatial sampling and mapping the distribution of this insect. The study was conducted for three growing seasons in Gharamalek, an agricultural region to the west of Tabriz, Iran. Weekly sampling began when E. integriceps adults migrated to wheat fields from overwintering sites and ended when the new generation adults appeared at the end of season. The adults were sampled using 1- by 1-m quadrat and distance-walk methods. A sweep net was used for sampling the nymphs, and five 180° sweeps were considered as the sampling unit. The results of spatial analyses by using geostatistics and SADIE indicated that E. integriceps adults were clumped after migration to fields and had significant spatial dependency. The second- and third-instar nymphs showed aggregated spatial structure in the middle of growing season. At the end of the season, population distribution changed toward random or regular patterns; and fourth and fifth instars had weaker spatial structure compared with younger nymphs. In Iran, management measures for E. integriceps in wheat fields are mainly applied against overwintering adults, as well as second and third instars. Because of the aggregated distribution of these life stages, site-specific spraying of chemicals is feasible in managing E. integriceps.
Asunto(s)
Hemípteros , Animales , Sistemas de Información Geográfica , Irán , Dinámica Poblacional , Estaciones del AñoRESUMEN
Three Colorado potato beetle, Leptinotarsa decemlineata, populations, from Ardabil, Bostanabaad and Ajabshir, were collected from potato fields in East Azarbaijan and Ardabil provinces in Iran and assayed for resistance to endosulfan. Possible resistance mechanisms were investigated using synergism studies and biochemical assays. Laboratory tests showed that the Bostanabaad strain was 220 and 109 times resistant compared with the susceptible strain in 2003 and 2004, respectively. The resistance ratios for the Ajabshir and Ardabil strains were 19 and 18, respectively. Since considerably more resistance was observed in the Bostanabaad strain compared with the other two, further investigation of the origin of resistance was done on this strain. Two insecticide synergists, piperonyl butoxide and S,S,S-tributylphosphorotrithioate, reduced resistance 2.3 and 3.5 times, respectively. These small degrees of synergism suggest that metabolism is not the source of the considerable difference in susceptibility between the two strains. This was supported by the results obtained from the biochemical assays that showed that glutathione S-transferase activity in the Bostanabaad strain did not significantly differ from the susceptible strain. These results suggest that target site insensitivity may be involved.
Asunto(s)
Escarabajos , Endosulfano , Resistencia a los Insecticidas , Insecticidas , Animales , Escarabajos/enzimología , Glutatión Transferasa/metabolismo , Irán , Larva , Organotiofosfatos , Butóxido de Piperonilo , Especificidad de la EspecieRESUMEN
Results of laboratory experiments are reported that tested the effects of five chitin synthesis inhibitors, diflubenzuron, cyromazine, lufenuron, hexaflumuron and triflumuron. on second instars of the Colorado potato beetle, Leptinotarsa decemlineata (Say) (Coleoptera: Crysomelidae), originally collected from potato fields of Bostanabaad, a town 66 km southeast of Tabriz, Iran. In bioassays, the larvae were fed potato leaves dipped in aqueous solutions containing chitin synthesis inhibitors. The mortalities and abnormalities of the treated larvae were recorded 72 hours after treatments. LC(50) values were 58.6, 69.6, 27.3, 0.79 and 81.4 mg ai/ L for diflubenzuron, cyromazine, lufenuron, hexaflumuron and triflumuron, respectively. Compared with phosalone, which is one of the common insecticides used for controlling this pest in Iran, lufenuron and hexaflumuron seem to be much more potent, and if they perform equally well in the field, they would be suitable candidates to be considered as reduced risk insecticides in management programs for L. decemlineata due to much wider margin of safety for mammals and considerably fewer undesirable environmental side effects.
Asunto(s)
Quitina/antagonistas & inhibidores , Escarabajos , Insecticidas , Animales , Benzamidas , Diflubenzurón , Larva , Dosificación Letal Mediana , Compuestos Organotiofosforados , Compuestos de Fenilurea , TriazinasRESUMEN
The present work deals with photocatalytic degradation of an organophosphorus pesticide, phosalone, in water in the presence of TiO2 particles under UV light illumination (1000 W). The influence of the basic photocatalytic parameters such as pH of the solution, amount of TiO2, irradiation time, stirring rate, and distance from UV source, on the photodegradation efficiency of phosalone was investigated. The degradation rate of phosalone was not high when the photolysis was carried out in the absence of TiO2 and it was negligible in the absence of UV light. The half-life (DT50) of a 20 ppm aqueous solution of phosalone was 15 min in optimized conditions. The plot of lnC (phosalone) vs. time was linear, suggesting first order reaction (K=0.0532 min(-1)). The half-life time of photomineralization in the concentration range of 7.5-20 ppm was 13.02 min. The efficiency of the method was also determined by measuring the reduction of Chemical Oxygen Demand (COD). During the mineralization under optimized conditions, COD decreased by more than 45% at irradiation time of 15 min. The photodegradation of phosalone was enhanced by addition of proper amount of hydrogen peroxide (150 ppm).
Asunto(s)
Insecticidas/química , Compuestos Organotiofosforados/química , Fármacos Fotosensibilizantes/farmacología , Titanio/farmacología , Contaminantes Químicos del Agua/análisis , Peróxido de Hidrógeno/farmacología , Concentración de Iones de Hidrógeno , Insecticidas/análisis , Insecticidas/efectos de la radiación , Cinética , Compuestos Organotiofosforados/análisis , Compuestos Organotiofosforados/efectos de la radiación , Oxidación-Reducción , Tamaño de la Partícula , Fotólisis , Rayos UltravioletaRESUMEN
A 2.2-kb full length cDNA containing an ORF encoding a putative acetylcholinesterase (AChE) precursor of 673 amino acid residues was obtained by a combined degenerate PCR and RACE strategy from an organophosphate-susceptible Bactrocera oleae strain. A comparison of cDNA sequences of individual insects from susceptible and resistant strains, coupled with an enzyme inhibition assay with omethoate, indicated a novel glycine-serine substitution (G488S), at an amino acid residue which is highly conserved across species (G396 of Torpedocalifornica AChE), as a likely cause of AChE insensitivity. This mutation was also associated with a 35-40% reduction in AChE catalytic efficiency. The I199V substitution, which confers low levels of resistance in Drosophila, was also present in B. oleae (I214V) and in combination with G488S produced up to a 16-fold decrease in insecticide sensitivity. This is the first agricultural pest where resistance has been associated with an alteration in AChE, which arises from point mutations located within the active site gorge of the enzyme.