Pathogenicity of Metarhizium anisopliae, Beauveria bassina and Paecilomyces fumosoroseus toward the horn fly Haematobia irritans (Diptera: Muscidae)

• Grant number: 05/04498-7
• Support Opportunities: Regular Research Grants
• Start date: June 01, 2006
• End date: August 31, 2008
• Field of knowledge: Biological Sciences - Microbiology - Applied Microbiology
• Principal Investigator: Antonio Carlos Monteiro
• Grantee: Antonio Carlos Monteiro
• Host Institution: Faculdade de Ciências Agrárias e Veterinárias (FCAV). Universidade Estadual Paulista (UNESP). Campus de Jaboticabal. Jaboticabal , SP, Brazil

Abstract

In 2004, Brazil became the top beef exporter, leaving near behind the United States, which was the market leader throughout history. However, losses brought by the main cattle ectoparasites in Brazil may reach 2 billion dollars a year. One major parasite is the horn fly Haematobia irritans, which has caused losses and a lot of concern to stockmen worldwide. The economic loss, estimated to be around 150 million dollars a year in Brazil, result from disturbs undergone by parasitized cattle, which affects beef yield. The control of H. irritans is almost exclusively based on chemical insecticide applications, and inevitably results in the selection of resistant individuals, decreasing control efficiency. In addition, this chemical control has affected horn fly natural enemies, such as parasitoids, predators and microorganisms, which are responsible for natural horn fly population control. Therefore, there is a growing need for studies to establish biological control methods that keep H. irritans populations below the economic loss level with no environment disequilibrium.There is a wide diversity of microorganisms in the environment. Entomopathogenic fungi are especially important because of their natural occurrence in many life stages of over 300 insect species, including important pests. Several works have reported the efficiency of entomopathogens on dipterans, but little is known about their pathogenicity on horn flies. Therefore, the present work aims to analyze the pathogenicity of Metarhizium anisopliae, Beauveria bassiana and Paecilomyces fumosoroseus isolates toward the horn fly Haematobia irritans. Isolates will be used at a rate of 5 x 108 conidia mL-1, on H. irritans eggs, larvae, pupae and adults, in bioassays conducted off-fecal mass. Through experimental data, the most promising isolates will be selected and tested at the rates 5 x 108, 5 x 109 and 5 x 1010 conidia mL-1, in eggs, larvae and pupae in cattle fecal masses. These first two steps of the work will be performed under lab conditions. Subsequently, a field experiment will be conducted with the best isolate of the second step. Conidia microcapsulated in alginate pellets will be offered to the animals at the concentration that produces the best result in the second experiment and 100-fold. After passing the gastrointestinal tract, conidia viability and larvae control in fecal masses will be evaluated. The experiments of the first step will be arranged in a completely randomized design, while second-step experiments will be arranged in a two-factor factorial (isolates and conidia concentration) versus control; the third step will be set in a split-plot design with treated and control groups as plots and sampling dates as split plots. The ANOVA will be performed with the F test and means will be compared by Tukey test at 5% of probability. (AU)