نوع مقاله : مقالات پژوهشی
دانشگاه شهید چمران اهواز
عنوان مقاله [English]
Introduction: Microcerotermes diversus Silvestri is considered the most economically destructive pest of wood products in Khuzestan, Iran. This species lives in subterranean nests and gains access to buildings and vegetation by constructing underground galleries. Therefore, control or management of this termite is of serious public concern. Generally, design and implementation of effective management methods for subterranean termites have faced some limitations due to their cryptic life habits. Millions of dollars have been spent for controlling termites worldwide, and 80% of these expenses relate to structural damage repair and costs expended for termite management. In recent years, the use of new non-repellent and slow-acting termiticides has become an important approach for subterranean termite control and has been gaining popularity. In recent years, an extensive survey on the foraging behavior of the most damaging subterranean termites of Khuzestan province (Iran) has been undertaken with a view to the development of appropriate strategies for control of M. diversus as an extremely destructive structural wood pest, was considered to be the major species with a wide distribution throughout Iran. This species tends to form secondary nests (with reproductive and brood).When the water table is high, secondary nests are usually built in above-ground sites such as tree trunks (adjacent to houses) and wall voids. Termite management has primarily focused on the use of chemical methods such as insecticide applications to soil around and beneath wooden structures. Soil treatments with organophosphates such as Chlorpyrifos (Dursban) did not persist in the environment for long time and proved ineffective against aerial colonies. Therefore, it is important to evaluate new compounds that have potential application for termite management. The main purpose of this study was to evaluate possible delayed toxicity effects of N’N napthaloylhydroxyamine (NHA; A. Johnson Metthey Company, USA) on feeding and mortality on M. diversus.
Materials and Methods: Termites (M. diversus), which were collected from infested wooden blocks previously buried in soil, transferred to the laboratory and placed in plastic boxes in a dark incubator at 28±2˚C and 90±5% relative humidity. Only active and healthy termites were used for tests. Feeding inhibition and mortality of workers treated with NHA were evaluated using both ‘choice’ and ‘no-choice’ test. In no-choice tests, termites were provided by only NHA-treated soil, or NHA-treated filter paper alone. Therefore, they could not escape the treated soil, or had only treated filter paper for food. In choice tests, termites were provided both treated and non-treated soil or filter paper, and could escape or avoid the treated substractes concentration. Technical NHA (99% wt:wt) was used. Two formulations, which were powdery and aqueous, were evaluated to envistigate their efficacy for management of M. diversus. Termites were exposed to NHA at concentrations which included ranging from 0.5 to 4.0% (wt:wt) in aqueous formulation, and from 0.5 to 8.0% (wt:wt) in powdered formulation. Termites were exposed to sterilized soil or filter paper treated with mentioned concentrations of NHA. Termites’ behaviors monitored daily and their mortality recorded. Mortality data were corrected using Abbott’s formula. ANOVA was performed in conjunction with a least significant difference (LSD) test, and Duncan’s Multiple Range Test at the 5% level using SAS software (ver. 9.1). A probit analysis was also conducted. The related diagrams were drawn using Microsoft Excel 2007. Noted that the tests were carried out with regard to the standards E1-06 (2006) of the USA and prEN117(2003) of the Europe.
Results and Discussion: NHA-treated-soil indicated that over 21 days, mortality rate gradually increased with increasing concentration levels. Trials with filter paper impregnated with the aqueous formulation showed that within 14 days mortality also gradually increased with increasing concentration. Probit analysis indicated that the level of mortality was dependent on concentration. There was an inverse relationship between time to 90% mortality (LT90) and concentration. LC50 and LC90 values when for compared between different tests showed that in no-choice tests where termites were forced to contact NHA, these values are lower compared with the choice tests. This indicates greater lethality in no-choice tests. Overall, at doses of 0.5, 1.0, 2.0, and 4.0% aqueous formulation (treated-filter paper), within 7 to 14-days mortality was 63%. Powdered formulation at doses of 0.5, 1.0, 2.0, 4.0, 6.0 and 8.0% (treated-soil) caused 67% mortality within 14 to 21 days, indicating that NHA is a slow-acting toxin once ingested.
Conclusion: With regard to our results, we suggest NHA as an effective non-repellent termiticide for controlling M. diversus, and perhaps other subterranean termites in soil. We suggest that application of NHA may be an effective strategyfor the control of M. diversus. Further, field testing is warranted to determine NHA efficacy in natural conditions.
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