Assessment of insecticide resistance in five insect pests attacking field and vegetable crops in Nicaragua.

Field populations of Hypothenemus hampei (Ferrari), Plutella xylostella (L.), Spodoptera exigua (Hübner), Helicoverpa zea (Boddie) and Bemisia tabaci (Gennadius) were tested for resistance to several insecticides commonly used in Nicariagua. Assays were conducted to estimate the LD50s or LC50s and the corresponding resistance ratios. A diagnostic concentration was used to discriminate between susceptible and resistant strains of H. hampei. The tests with >6,000 H. hampei adults collected from six different sites indicate the absence of resistance to endosulfan. Resistance to cypermethrin, deltamethrin, chlorfluazuron, thiocyclam, and methamidophos was documented in six field populations of P. xylostella. High levels of resistance to cypermethrin and deltamethrin, but moderate levels of resistance to chlorpyriphos and methomyl, were also documented in two field populations of S. exigua. Moderate levels of resistance to cypermethrin, deltamethrin and chlorpyriphos were also documented in three field populations of H. zea. Moderate to high levels of resistance to bifenthrin, methamidophos and endosulfan were documented in four field populations of B. tabaci. The presence of significant correlations between LD50s or LC50s suggests the occurrence of cross-resistance or simultaneous selection for resistance by different insecticides with different modes of action. Our data could not differentiate between these two possibilities. Because insecticides will continue being used in Nicaragua, a resistance management program is urgently needed. The implementation of integrated pest management tactics must be accompanied by specific regulations for pesticide registration. In the future, pesticide registration regulations in Nicaragua should include periodic resistance monitoring. The mechanisms to cover the costs of resistance monitoring and resistance management should also be established.

An epidemic of pesticide poisoning in Nicaragua: implications for prevention in developing countries.

OBJECTIVES: The purpose of this study was to demonstrate the usefulness of the Northwestern Nicaraguan Ministry of Health surveillance system for detecting pesticide poisonings. METHODS: Cases were reported to the regional department of epidemiology through daily telephone reports and through monthly consolidated reports from each of the 18 health centers of the National Health Service. Reporting forms were also distributed to the four area hospitals. RESULTS: During June and July 1987, an epidemic of 548 pesticide poisoning was detected in northwestern Nicaragua. Seventy-seven percent of the poisonings were caused by carbofuran or methamidophos. Of the work-related cases (91% of reported poisonings), more than 80% occurred among maize farmers and on small to medium land holdings (fewer than 140 hectares). Nineteen percent of the work-related cases involved children under 16 years of age. CONCLUSIONS: Unsafe working conditions such as manual application of pesticides and the use of backpack sprayers, the introduction of a hazardous powdered formulation of carbofuran highly restricted in the developed world, and agricultural subsidies that encouraged the use of hazardous pesticides all contributed to the epidemic.

Intra-oral welding of implants for an immediate load with overdentures.

Different clinical applications of the Hruska intra-oral welding machine have been described in previous articles (Hruska, 1986, 1987, 1988, 1989a,b). These applications were related to over 100 cases of the use of non-submergible implants. This paper will describe a revised application of this machine as used with the currently popular multiform submergible implants widely used in the United States. The intra-oral welding is performed immediately after suture placement, with one or more connecting titanium wires serving as the splinting medium. This permits the patient to leave the office with a stable and retentive overdenture resting securely on the newly created splint performed the same day of surgery. This avoids the potentially troublesome problem of allowing the overdenture to be supported by the recently altered soft tissues. In addition, the patient otherwise would not have the use of a denture during the bone-healing period, which creates an alteration in psychological as well as physiological status. The disadvantages of immediate loading are counteracted by the splinting and load-sharing. This encourages the bone around the implants to reorganize and remodel according to Wolff's law, as demonstrated by De Angelis (1970) and Dalin and Olsson (1974). Different studies (Sutter et al., 1983a,b; Schroeder, 1985; Jennings, 1991) have shown that the ankylotic connection between one-stage titanium ITI implants and bone (so-called osseointegration) occurs and is maintained under load.

Quality criteria for pure titanium casting, laboratory soldering, intraoral welding, and a device to aid in making uncontaminated castings.

Procedures for casting, laboratory soldering, and intraoral welding of titanium for dental restorations are described and illustrated. Pure titanium and titanium 6A1-4Va alloy castings may be used for virtually any prosthodontic rehabilitation as well as for implants, with the proper equipment and technique.

A novel method for vacuum casting titanium.

A new method for vacuum casting titanium is described. The device allows decontamination of the mold before placing it into the casting machine. After wax elimination, the mold is placed into the device and sealed with a thin film of titanium. The air is evacuated from the mold, and it is flushed with helium. The process is repeated, and the casting is made when convenient.