Nasri S. Kawar

Isolation of Beauveria species from Lebanon and evaluation of its efficacy against the cedar web-spinning sawfly, Cephalcia tannourinensis

Larvae of the cedar web-spinning sawfly, Cephalcia tannourinensis Chevin (Hymenoptera: Pamphiliidae), infected with a white fungus were collected from the Tannourine-Hadath El-Jebbeh cedar forest. Macro- and micro-morphological data based on the examination of colonies, conidiophores, and conidial shape of the fungus suggested a Beauveria species. Sequence analysis of the internal transcribed spacer regions of the isolated fungus showed that it is most closely related to isolates of B. bassiana Clade C. The present study showed that the isolated B. bassiana is a naturally occurring entomopathogenic fungus parasitizing the larvae of C. tannourinensis in Lebanon. Laboratory bioassays showed that B. bassiana caused high mortality of eggs and larvae. The infected eggs turned brownish in color, while larvae of the first instar ceased feeding and showed immobility and rigidity within 5 days and before sporulating conidial mat appeared on their cuticle. Second and third larval instars took longer time to show fungal sporulation: mortalities ranged between 85 and 100% within 7 days when treated with different conidial concentrations. The efficacy of control of C. tannourinensis using B. bassiana was higher or equal to the reference insect growth regulator, diflubenzuron, suggesting the possibility of its success as a biological control agent.

Behavior of parathion in apple juice processed into cider and vinegar

Apple juice, fortified with 25 ppm (ug/g) of parathion, was processed into cider and vinegar. After the initial fermentation period of 12 days, the supernatant cider contained 7.4 ppm of parathion while the level in the sedimented lees was 88 ppm. Sorption to the sedimented matter was the main pathway for parathion residue reduction in the cider. Levels of aminoparathion and 4-nitrophenol, the only metabolites of parathion detected as confirmed by thin-layer chromatography, were 0.19 and 1.2 ppm, respectively, in the cider. The 56-day-old finished cider prior to bottling contained 2.2 ppm parathion, 0.15 ppm aminoparathion and 1.3 ppm 4-nitrophenol. Storage of the cider at 24, 12, 4 and -20 degrees C resulted in further reduction in the parathion levels. After one year, samples stored at 24 degrees C contained only 2.5% of the initial level added to the juice. Samples stored at the three other temperatures contained about 5% of the original level. Vinegar formed after 57 days of fermentation contained 5.1 ppm parathion, while the residue level in the lees was 76 ppm. Aminoparathion and 4-nitrophenol levels were 0.23 and 1.2 ppm, respectively in the vinegar. Storage of the vinegar at 24 degrees C for one year resulted in a gradual decline in the parathion level and at the end of the storage period, the remaining residue represented about 6% of the initial 24 ppm added to the juice.

Degradation of Metribuzin in Two Soil Types of Lebanon

The degradation of metribuzin [4-amino-6-tert-butyl-3-methylthio-1,2,4-triazin-5(4H)-one] as influenced by soil type, temperature, humidity, organic fertilizers, soil sterilization, and ultra-violet radiation was studied in two soil types of Lebanon under laboratory conditions. The two soil types were sandy loam and clay. Deamination of metribuzin in the sandy loam soil to its deaminometribuzin (DA) derivative was basically a result of biological activity. In the clay soil the first metabolite diketometribuzin (DK) was a result of oxidative desulfuration, while diketo-deaminometribuzin (DADK) was the product of reductive deamination. The two soils represented major differences in the pesticide transformation processes. Photodecomposition on the soil surface and in aqueous media was also an important process in the degradation of metribuzin. Furthermore, the increase in soil organic matter enhanced degradation.

DDT residues in Lebanese soils.

Abstract The present study was conducted to evaluate the levels of residual DDT in Lebanese soils. A total of 113 surface soil samples were collected for analysis from three major agricultural regions in the country: Mount Lebanon, Beqa’a valley and the coastal plain. The values of residual DDT in soils ranged between 0 and 1190 ng g−1. The majority of the analyzed soil samples were free or contained very low concentrations of DDE. Only two surface soil samples, which were collected from urban areas with high human activities, contained relatively high concentrations of residual DDT. The levels of residual DDT in all of the analyzed soil samples were within the permissible limits for agricultural soils.

Biodegradation of α and β Endosulfan in Soil as Influenced by Application of Different Organic Materials

Abstract A laboratory pot experiment was conducted to study the effect of amending soil with four different sources of organic matter on the degradation rate of α and β endosulfan isomers. Poultry by-product meal, poultry manure, dairy manure, and municipal solid waste compost were cured, dried, ground (<1 mm) and thoroughly mixed with a calcareous soil at a rate of 2% and placed in plastic pots. Endosulfan was added at the rate of 20 mg kg−1. The moisture level was kept near field capacity and the pots were kept at room temperature. Soil sub-samples, 100 g each, were collected from every pot at days 1, 8, 15, 22, 29, 43, and 57 for the measurement of endosulfan isomers. Endosulfan residues were extracted from the soil samples with acetone. The supernatant was filtered through anhydrous sodium sulphate, 5 mL aliquot was diluted to 25 mL with hexane, mixed well, and then two sub-samples from the filtrates were analyzed for α and β endosulfan isomers by gas chromatography. The results indicated that the half-life (T ½) of α-endosulfan in the poultry by-product meal treatment was 15 days compared to about 22 days in the other treatments. The T ½ of β-endosulfan was 22 days in the poultry by-product meal treatment and followed a bi-phasic pattern, 57 days in the municipal solid waste compost treatment and the extrapolated T ½ was about 115 days for the other three treatments.

Behavior of triadimefon in two Lebanese soils.

The retention and fate of triadimefon fungicide were studied under two environmental conditions. Field studies were conducted on two soils, a sandy loam soil (Fanar) and a clay soil (Raouda). Fanar is a wet coastal area while Raouda is a dry agricultural area of the Bekaa plain located at an elevation of 870 m above sea level. Triadimefon was applied with a jet sprayer at 267 g a.i.ha−1 and 200 g a.i.ha−1 at Fanar and Raouda, respectively. Reconstituted soil columns (600 × 30 mm) glasses, were used to study the fungicide movement and metabolism in the two soils. Analyses of triadimefon and its metabolites were carried out using gas chromatography (GC) and high performance liquid chromatography (HPLC). The results indicated a weak reversibility of the adsorbed fraction in the clay soil. Clay is considered an important factor in triadimefon adsorption. Triadimefon mobility in the sandy—loam soil was relatively high in comparison with behavior in the clay soil where about half of the applied fungicide was detected in the upper 25 cm of soil, six days after treatment. Rapid degradation of triadimefon to triadimenol was observed in the two soils. The observed half-life was 8 days in sandy-loam and 13 days in clay soils.

Behavior of parathion in tomatoes processed into juice and Ketchup

Fresh tomatoes were cut, fortified with 25 ppm (micrograms/g) of parathion (0,0-diethyl 0-4-nitrophenylphosphorothioate) and processed into either juice or ketchup. Tomato juice was canned, while ketchup was placed in bottles. All samples were stored at room temperature for analysis at two-monthly intervals. Parathion residues were measured quantitatively by GLC, while the two metabolites, aminoparathion (0,0-diethyl 0-4-aminophenylphosphorothioate) and 4-nitrophenol, were determined colorimetrically. The presence of the three compounds was confirmed qualitatively by TLC. Blanching of tomatoes resulted in about 50% reduction of parathion level. Pulping of fruits caused a further decrease in parathion residues in juice as a result of its sorption and concentration in the semi-solid pulp. About 85% of parathion added to tomatoes was lost during the processing steps. Storage of juice resulted in a gradual decrease in parathion levels, whereby only 1.7% of the original amount was detected after six months of storage. The compound was stable in ketchup for the first four months of storage but decreased thereafter to almost 7% of the original quantity added to fruits. Aminoparathion and 4-nitrophenol were detected in low levels.

Fate of DDT and parathion in grapes processed into arak, an alcoholic beverage.

Arak, the national alcoholic drink in Lebanon, was prepared from grapes to which either DDT or parathion had been added. Samples of the nine fractions produced from the fermentation and distillation steps were analyzed for DDT and parathion and their respective metabolites. DDT degraded to DDD during the fermentation step resulting in a sharp decrease in DDT level. The two distillation steps contributed to a further decrease in the DDT level so that the final product contained less than 2% of the amount found in the fresh grape juice. Although the concentration of DDD increased sharply during fermentation, it also decreased to a negligible level during the subsequent distillation procedure. Parathion was more stable than DDT during the fermentation and first distillation steps. However, the second distillation process caused a sharp decline in its level and the Arak contained only about 6% of the residues present in the fresh juice, paranithophenol being the only metabolite detected.

Comparison of gas chromatography and immunoassay methods in quantifying fenitrothion residues in grape juice processed into alcoholic drinks

Wine and Arak, the national alcoholic drink in Lebanon, were prepared from grape juice fortified with fenitrothion to a concentration of 20ppm. Samples of the 11 fractions produced by the fermentation and distillation steps were analyzed for fenitrothion residues using gas chromatography (GC) and enzyme-linked immunosorbent assay (ELISA). Results of residue analyses showed that the two techniques were highly correlated (r = 0.978) and indicated that fenitrothion was stable during the fermentation steps but not during distillation. The clarified wine 35 days later contained about 85% (15.3 ppm) of the fenitrothion concentration found in the juice as determined by GC analysis. Arak was prepared by a two-steps distillation of the clarified wine. The alcohol distillate and undistilled fraction from the first distillation contained 2.5 ppm and 5.8 ppm of fenitrothion, respectively. No fenitrothion residues were detected by both techniques in the four fractions collected from the second distillation step.

Evidence of sexual attraction by pheromone in the cedar web-spinning sawfly

The cedar web-spinning sawfly, Cephalcia tannourinensis Chevin (Hymenoptera: Pamphiliidae), is a pest that has been causing serious damage to cedar (Cedrus libani) forests in Lebanon since 1990. The existence of a sex pheromone was shown in field experiments in a cedar forest in Lebanon and in laboratory tests in olfactometers with and without airflow. More males were caught in traps baited either with virgin females or with a hexane extract of the whole female body than in traps baited either with males alone or with mixed males and females. Male and female C. tannourinensis were active during the day. Mating and pheromone production were observed to occur during midday hours (1000–1400) in the field and under laboratory conditions. Olfactometer tests with extracts prepared from different body parts of the female indicated that the pheromone is produced in the abdominal region, and tests with different dilutions of female extract showed that the male response is dose-dependent.