Effects of a novel pesticide resistance management strategy on tick control in a smallholding exotic-breed dairy herd in Kenya

Effects of a novel pesticide resistance management strategy on tick control are evaluated in this study. The study is based on a temporal analysis of tick management practices on a smallholding in western Kenya. Results are reported of an innovation to tackle individual resistance in a pair of alternative pesticides using relay application. Incidence of tick-borne diseases at the farm was reduced from 79.6% per annum to 4.5% and no cases were observed in the last two years of the study. Negative cross-resistance is believed to be the mechanism in play for this effective tick control practice. Tick-borne disease control and management costs were halved in comparison to application of a single ineffective pesticide at the same treatment frequency. The acaricide relay strategy is suitable for smallholdings and is expected to significantly extend the useful lifespan of the pesticide pair

Relative stability, performance, and superiority of crop genotypes across environments

Assessments of the stability as well as the performance of plant genotypes across diverse environmental conditions are important to plant breeders and agronomists as tools for selecting superior cultivars for the target environments. In this study, the shortcomings of fitted response as an indicator of relative stability are discussed and use of a genotype environment correlation coefficient, rge, as a measure of relative stability is proposed. Two other relevant indices are introduced: performance index, pi, and superiority index, si. The latter is a compound index for stability and performance that provides a simple method for selecting superior genotypes for relevant environments. In application, a distinction is made between specific stability (over space and microclimate) and general stability (over space and time) depending on the format of the specified environmental index. A statistical significance test for relative stability is considered and three datasets are used to demonstrate the application of derived indices under varying environment combinations. Appraisal of the method and some currently appealing procedures applied to the same dataset reveal a general concordance under similar conditions. The introduced parameters prove to be simple, convenient tools for examining data from plant adaptation trials in the presence of genotype x environment interaction

A parametric measure of lactation persistency in dairy cattle

Current measures of lactation persistency are not uniformly applicable to the variety of lactation curves for individual cows. Moreover, they are either difficult to interpret or are functions of lactation yield and therefore inappropriate. In this study, a simple, robust parametric measure is derived from a perfect fit of cumulative milk yield data to quadratic curves. The curvilinear model is appropriate for trend analysis, a major manifestation of which is persistency. Data fitted to the model were obtained from a total of 194 lactations of 169 cows in 5 mixed-breed herds under conditions varying from a small holding herd in the tropics to research herds in Italy. A negative association between persistency and total lactation yield was observed. The proposed lactation persistency model could result in more accurate estimates and better insight into this trait