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| Author(s): |
Everaldo Batista Alves
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Piracicaba. , gráficos, ilustrações, tabelas. |
| Institution: | Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC) |
| Defense date: | 2004-04-19 |
| Examining board members: |
Celso Omoto;
Gustavo Adolfo Astua Monge;
Carlos Amadeu Leite de Oliveira;
Paulo Rebelles Reis;
Pedro Takao Yamamoto
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| Advisor: | Celso Omoto |
| Field of knowledge: | Agronomical Sciences - Agronomy |
| Indexed in: | Banco de Dados Bibliográficos da USP-DEDALUS; Biblioteca Digital de Teses e Dissertações - USP |
| Location: | Universidade de São Paulo. Biblioteca Central da Escola Superior de Agricultura Luiz de Queiroz; t632.6542; A474d; 83140 |
| Abstract | |
The knowledge of dynamics of pest resistance to pesticides is crucial for the implementation of resistance management strategies. Therefore, the main objective of this research was to study the dynamics of the resistance of Brevipalpus phoenicis (Geijskes, 1939) to the acaricide dicofol in commercial citrus groves during a 3-year period. Studies to evaluate the selection response to dicofol were conducted in populations of B. phoenicis with different initial resistance frequencies. The frequency of resistance was also estimated in the absence of selection pressure. Some factors that influence the resistance dynamics of B. phoenicis such as the dispersal capacity and the effectiveness of alternative hosts as refuges for susceptible individuals were also evaluated in this study. There was a significant increase in the frequency of dicofol resistance with applications of dicofol in some citrus field plots. The rate of reset to susceptibility in the absence of selection pressure varied from field to field. In some fields, the reset to susceptibility was observed within approximately 12-month period. On the other hand, the reset to susceptibility was not observed even after 29 months without using dicofol. Dispersal studies of B. phoenicis on sandy surface conducted under greenhouse conditions showed that dispersal capacity by crawling is limited. After the release of 6,000 mites in one point, only 3% reached distances of 40 to 50 cm from the release point. This mite moved less than 1 cm.day-1. Wind speed of 23 km.h-1 was not enough to carry mites from citrus fruit surface under laboratory conditions; and wind speeds of 30 and 40 km.h-1 were capable to carry less than 1% of mites either from new or old mite colonies on fruits. Mite dispersal studies with the use of sticky traps under field conditions also showed that B. phoenicis dispersal is very limited when compared to other mite species that occur in citrus groves. From a total of 2,420 and 661 mites collected from two citrus fields in Descalvado-SP region, only 0.45 and 11.80% of mites were in the Tenuipalpidae family, respectively. In order to evaluate the effectiveness of other host plants of B. phoenicis as refuges for susceptible individuals, the genetic variability in populations of B. phoenicis from "sansão-de-campo" (Mimosa caesalpiniaefolia Benth.) located near the citrus groves was evaluated by the estimation of resistance frequencies to dicofol and by molecular techniques. In general, the frequency of resistance to dicofol in populations of B. phoenicis from "sansão-de-campo" was lower than that from citrus groves. However, the analysis of genetic variability with RAPD-PCR revealed that B. phoenicis populations from "sansão-de-campo" were genetically different from citrus groves. Based on our results, we concluded that the reset of susceptibility of B. phoenicis to dicofol is very variable and the immigration of susceptible individuals from untreated areas or alternative hosts is very limited. (AU) | |