Efficacy Of Individual Treatments Research Articles

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.

Cereal Leaf Beetle and Aphid Control in Late-Planted Soft Red Winter Wheat, 1987

Abstract Four insecticidal treatments were evaluated to determine their efficacy in controlling cereal leaf beetle and aphid population densities in soft red winter wheat. Foliar insecticides were applied on 11 May on ‘Pioneer 2551’ wheat planted on a 7-inch row spacing 10 Jan at Midway Farm in Richmond County, Va. Plots were 12 × 30 ft with a 3-ft alle&amp;gt; between treatments. Treatments were arranged in a randomized block design with 4 replications. Spray concentrates were applied with a C02-powered compressed-air sprayer at 32 psi that delivered 31.8 gal/acre by means of flat-fan Teejet AL8004 nozzels. The efficacy of individual treatments was determined 1, 3, 5, 7, and 14 days after application by inspecting whole plants for the presence of live cereal leaf beetle (CLB) larvae and aphids per row-ft. Yield estimates were obtained harvesting 9 30-ft-long rows from each plot with a small-plot combine. Yields were adjusted to 14% moisture. A Li-Cor LI3000 area meter was used to determine leaf areas of the flag and 2nd leaves and percent defoliation of 40 random plants/treatment.

Cereal Leaf Beetle Control in Soft Red Winter Wheat, 1986

Abstract Four insecticidal treatments were evaluated to determine their efficacy in controlling cereal leaf beetle larvae populations in soft red winter wheat. Foliar insecticides were applied on 7 May ‘86 on ‘Saluda’ wheat planted on 18 Oct, ‘85 at the Vernon Delano Farm in Richmond County, VA. Plots were 6 ft by 25 ft with a 5-foot alley between treatments. Treatments were arranged in a randomized block design with three replications. Spray concentrates were applied with a CO2-powered compressed air sprayer at 32.8 psi that delivered 32.6 gal of finished formulation per acre. Flat Fan, Tee Jet AL8002, nozzles were utilized. The efficacy of individual treatments was determined 1-, 5-, 7-, 12-, and 16-days after application by inspecting whole plants for the presence of live larvae per 10 culms. Yield estimates were obtained from 20 ft of row collected from the two center rows of each plot. Yields were adjusted to 14% moisture.

Aphid Control in Spring Oats, 1985

Abstract Foliar insecticides were applied on 30 May ‘85 at the Russell Settle Farm in Richmond County, Virginia. Oats were planted on a 7-inch row spacing on 11 Mar ‘85. A completely random design was utilized with 3 replications. Individual plots were 6 × 50 feet with a 1-foot border between treatments. Spray concentrate was applied with a CO2 air sprayer at 22 psi that delivered 11.7 gal of finished formulation per acre. Flat Fan, Tee Jet AL8002, nozzels were used. The efficacy of individual treatments was determined 1-, 5-, 7-, and 14-days after treatment by inspecting all grain heads per 1 row-foot for the presence of live aphids.

Armyworm Control in Wheat, 1985

Abstract Three insecticidal treatments were evaluated to determine their efficacy in controlling armyworms in soft red winter wheat. Foliar insecticides were applied on 22 May on small grain grown on the Eastern Virginia Research Station in Richmond County, VA. A completely random experimental design was incorporated with 3 replications. Individual plots were 50 × 6 ft spaced 12 ft apart. Spray concentrate was applied with a CO2 sprayer at 22 psi that delivered 11.7 gal of finished formulation per acre. Flat Fan, Tee Jet AL8002, nozzles were used. The efficacy of individual treatments was determined 1, 7, and 14 days after application by inspecting 3 row-ft (on both sides of a single row) for the presence of live armyworm larvae.

Cereal Leaf Beetle Control in Spring Oats, 1985

Abstract Two insecticidal treatments were evaluated to determine their efficacy in controlling cereal leaf beetle larvae in spring-planted oats. Insecticides were applied at peak oviposition on May 7 at the Russell Settle Farm near Warsaw, VA. A randomized block design was utilized with 4 replications. Individual plots were 12 × 50 feet with 3-foot alleys. Each spray concentrate was applied to the oat foliage with a CO2 compressed air sprayer at 22 psi with Flat Fan, Tee Jet AL8002 nozzles that delivered 11.7 gal of finished formulation per acre. The efficacy of individual treatments was determined 1-, 3-, 7-, and 14-days after application by inspecting whole plants for the presence of live larvae per 10 culms. The leaf area and percent defoliation of the flag, second, and third leaves was determined on Jun 4 by clipping whole plants and immediately measuring each leaf with a Li-Cor LI-3000 area meter. The 2 center rows of each plot were harvested for yield estimates, which were adjusted to 14% moisture.