Percolation-intercropping strategies to prevent dissemination of phytopathogens on plantations.

Phytophthora is one of the most aggressive and worldwide extended phytopathogens that attack plants and trees. Its effects produce tremendous economical losses in agronomy and forestry since no effective fungicide exists. We propose to combine percolation theory with an intercropping sowing configuration as a non-chemical strategy to minimize the dissemination of the pathogen. In this work, we model a plantation as a square lattice where two types of plants are arranged in alternating columns or diagonals, and Phytophthora zoospores are allowed to propagate to the nearest and next-to-nearest neighboring plants. We determine the percolation threshold for each intercropping configuration as a function of the plant's susceptibilities and the number of inoculated cells at the beginning of the propagation process. The results are presented as phase diagrams where crop densities that prevent the formation of a spanning cluster of susceptible or diseased plants are indicated. The main result is the existence of susceptibility value combinations for which no spanning cluster is formed even if every cell in the plantation is sowed. This finding can be useful in choosing a configuration and density of plants that minimize damages caused by Phytophthora. We illustrate the application of the phase diagrams with the susceptibilities of three plants with a high commercial value.

Site-bond percolation solution to preventing the propagation of Phytophthora zoospores on plantations.

We propose a strategy based on the site-bond percolation to minimize the propagation of Phytophthora zoospores on plantations, consisting in introducing physical barriers between neighboring plants. Two clustering processes are distinguished: (i) one of cells with the presence of the pathogen, detected on soil analysis, and (ii) that of diseased plants, revealed from a visual inspection of the plantation. The former is well described by the standard site-bond percolation. In the latter, the percolation threshold is fitted by a Tsallis distribution when no barriers are introduced. We provide, for both cases, the formulas for the minimal barrier density to prevent the emergence of the spanning cluster. Though this work is focused on a specific pathogen, the model presented here can also be applied to prevent the spreading of other pathogens that disseminate, by other means, from one plant to the neighboring ones. Finally, the application of this strategy to three types of commercially important Mexican chili plants is also shown.

[Compliance with preventive activities at a primary care center]. / Cumplimento de actividades preventivas en un centro de atención primaria.

OBJECTIVES: To evaluate the level of fulfillment of a number of prevention schemes carried out by the primary care team and to analyze the influence of some factors in the patients when fulfilling such schemes. DESIGN: Descriptive crossover study. SETTING: Primary Care. Health centre of Rekaldeberri, Bizkaia. PATIENTS AND OTHER PARTICIPANTS: 180 clinical records formed by patients from 14 to 64 years old. MEASUREMENTS AND MAIN RESULTS: The percentage of clinical records in which the scheme carried out was correct was: blood pressure 57%, tobacco 41.1%, alcohol 24.5%, cholesterol 60%, height 32.8%, and weight 38.9%. A thorough study of the prevention scheme was carried out in patients who presented recorded pathology (high blood pressure and hypercholesterolemia). In some cases was recorded that there were some differences with regard to age and sex. CONCLUSIONS: We have to develop continuous training programmes in prevention schemes and revise the pattern of registration form, especially with regard to toxic habits.