Studies for the methodology development of in vivo production of the fungus Neozygites floridana Weiser and Muma to control the mite Tetranychus urticae Koch

Author(s)

Thiago Rodrigues de Castro

• Document type: Master's Dissertation
• Press: Piracicaba.
• Institution: Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC)
• Defense date: 2011-09-09

Examining board members

Italo Delalibera Junior; Gilberto José de Moraes; Drauzio Eduardo Naretto Rangel

• Advisor: Italo Delalibera Junior

Abstract

One of the main pest mite species is the Twospotted Spider Mite, Tetranychus urticae. The most important natural enemy of this mite is the pathogen Neozygites floridana. To enabling the use of this pathogen through inoculative releases, basic information is still needed to support the large scale methodology development for fungus production and release in the field. It was determined in the laboratory, the humidity and temperature requirements for fungus sporulation, by placing mummified mites on Jack-bean leaves. There was no sporulation at any of the temperatures tested (13, 17, 21 and 25°C) at 80% and 85% RH. The fungus had low sporulation at 90% RH at all temperatures. The best conditions for the capilloconidia development were 95% and 100%RH at 21°C and 25°C. Mummified mites were placed to sporulate in Jack-bean plants inside screenhouses at different times of year and temperature and humidity were monitored. It was noted that above 13°C the fungus can produce a considerable number of primary conidia (> 130) even at 90%RH. However, only at 90%RH and 25°C the capilloconidia production is significant (> 389). It was determined the effect of exposure of two light intensities (2.960 Lux and 15.392 Lux), three photoperiods (24h of light, 12:12h(L:D) and 24h of darkness) and two temperatures (18°C and 23°C), on the production of primary conidia and capilloconidia of N. floridana isolates from Norway and Brazil. Fungus-killed cadavers by each of the isolates were exposed to different treatments in BOD. No differences were found between the two isolates in the two temperatures tested. The results for the 12:12h(L:D) were similar to those found for 24h of darkness. Light inhibition of capilloconidia formation was greater on Norwegian isolate. Low light intensity for 24h had a mild effect on sporulation of the two isolates, but strongly inhibited the formation of capilloconidia of the Norwegian isolate. Studies were carried out to evaluate the effect of pesticides used in production of strawberries in both countries on sporulation and capilloconidia production of N. floridana in the laboratory. The results showed that Tebuconazole and Fenpropatrin in the recommended concentration and Abamectin in half of the recommended concentration were the less aggressive to N. floridana. Attempts to scale production of this fungus were also made. Through experimental inoculations it was possible to induce epizootics of the fungus in T. urticae populations on Jack-beans, planted in pots in screenhouses. The most convenient way for inoculation of the fungus was to release four mummified mites per pot. Larger quantities of mummified mites by N. floridana were produced when climatic conditions were characterized by high RH and 20°C, during the winter production was inefficient. The use of light and fans at night during the end of the epizootic phase, was effective in inhibiting the sporulation of the fungus and ensure the quality of mummified mites for storage. Although it was possible to produce a large number of mummified mites, several studies are still needed to develop an economically viable methodology for large scale production for field use. (AU)

• FAPESP's process: 08/07358-0 - Development of methodology for production in vivo and release of the fungus Neozygites for the control of Tetranychus urticae Koch mite.
• Grantee: Thiago Rodrigues de Castro
• Support Opportunities: Scholarships in Brazil - Master