Trichlorfon Research Articles

Effects of water temperature and pH on toxicity of terbufos, trichlorfon, 4‐nitrophenol and 2,4‐dinitrophenol to the amphipod Gammarus pseudolimnaeus and rainbow trout (Oncorhynchus mykiss)

AbstractAcute toxicity tests were conducted to determine (a) the individual and interactive effects of water temperature (7, 12, 17°C), pH (6 5, 7 5, 8 5, 9 5), and time on the toxicity of terbufos, trichlorfon, 4 nitrophenol, and 2,4‐dinitrophenol to rainbow trout (Oncorhynchus mykiss) and the amphipod Gammarus pseudohmnaeus, and (b) the individual and interactive effects of water temperature and pH on chemical bioconcentration during acute tests with rainbow trout and Gammarus exposed to terbufos, 4 nitrophenol, and 2,4 dinitrophenol The toxicity of all four chemicals was significantly affected by pH in all tests, except for Gammarus exposed to terbufos The toxicity of terbufos to rainbow trout and Gammarus was less at pH 7 5 than at higher or lower pH The toxicity of both nitrophenols decreased as pH increased, whereas the toxicity of trichlorfon increased with pH The effect of pH on trichlorfon toxicity decreased with temperature Temperature significantly affected the toxicity of all four chemicals to both species Toxicity increased with temperature in all tests, except for rainbow trout exposed to nitrophenols, toxicity decreased as temperature increased for rainbow trout Chemical bioconcentration was also significantly af fected by temperature and pH and was directly related to toxicity in most tests Significant interactive effects between toxicity modifying factors were also frequently observed Temperature and pH effects on chemical toxicity need to be consid ered in chemical hazard assessment to ensure adequate protection of aquatic organisms

Disappearance of trichlorfon from cultures with different cyanobacteria

Disappearance of trichlorfon from cultures with different cyanobacteria

Interactions between trichlorfon and threeChlorophyceae

Interactions between trichlorfon and threeChlorophyceae

Phenothiazine in the origin of benzimidazole resistance in population-B equine strongyles

Clinical trials on a central Kentucky Thoroughbred Farm (B) during 1960–1961 involved nine test treatments of mares, yearlings and weanlings ( n = 124), and compared efficacies of phenothiazine (PTZ), piperazine (PPZ), mixtures of PTZ+PPZ and thiabendazole (TBZ) for (1) percent reduction and (2) complete clearance or graded reduction of strongyle egg per gram (epg) counts. Three grades of PTZ (N.F. green, micronized purified and 2–3-μm purified) at the dose rate of 55 mg kg −1 were ineffective in six tests; reduction of strongyle epg count were low grade (26%) and complete clearance was found in only 1 of 32 horses. Piperazine alone at 88 mg base kg −1 was efficacious in two tests; epg counts were effectively reduced (98%), but complete clearance was found in only 2 of 10 horses. Several mixtures of PTZ+PPZ with various dosages of PTZ (27.5–55 mg kg −1) plus PPZ base (88 mg kg −1) were quite effective in six tests, as epg counts were reduced by 96% and complete clearance occurred in 25 of 38 horses. Four trials with TBZ at dose rates between 13 and 44 mg kg −1 in 1961 reduced epg counts by 98%, but cleared only 15 of 36 horses. These data indicated: (1) a large segment of the Farm B small strongyle population was resistant to PTZ at the outset of these observations in 1960; (2) TBZ-resistant individuals were also present in this population when TBZ was first used in 1961. During the ensuing 4-year study (1962–1965) on Farm B mares ( n = 15 per year) and yearlings ( n = 15–17 per year), biweekly epg and larvae per gram (lpg) counts were carried out to compare the efficacy of three treatment programs: (1) monthly doses of TBZ at 26 mg kg −1; (2) monthly doses of TBZ at 13 mg kg −1; (3) bimonthly doses of a mixture of PTZ+PPZ and carbon disulfide (CS 2) at dose rates of 27.5+88 and 78 mg kg −1, respectively, or a mixture of PTZ+PPZ+trichlorfon (TCF) at dose rates of 27.5+88+40 mg kg −1, respectively. Emergence of a TBZ-resistant segment of the small strongyle infections was evaluated by three criteria: (1) annual mean strongyle epg counts; (2) efficacy of individual treatments for epg reductions (%); (3) complete clearance or graded reductions of strongyle epg counts. In contrast, treatments with PTZ+PPZ−CS 2 (mares) and PTZ+PPZ+TCF (yearlings) were efficacious. Both drugs produced relatively low average annual egg counts, efficacious reductions in epg counts and high rates of clearance or graded reductions of egg counts. For the latter, PTZ+PPZ−CS 2 was marginally more efficacious ( P < 0.05) than PTZ+PPZ+TCF. Multiple resistance of small strongyles in this population (B) was observed. Prior to 1960, long-term use of PTZ for strongyle control had led to selected PTZ-resistant small strongyles. Initial use of TBZ in 1961 produced effective epg reductions, but complete clearance data revealed the presence of TBZ-resistant small strongyles at the outset. Subsequently, the regimen of regular treatments with TBZ of ∼50% of the mares and yearlings resulted in the increasing dominance over time of the TBZ-resistant segment of the population of small strongyles. The population remained uniformly responsive to treatments with mixtures of PTZ+PPZ−CS 2 or PTZ+PPZ+TCF.