Selection of Beauveria spp. isolates for control of the termite Heterotermes tenuis (Hagen, 1858)

Abstract

Heterotermes tenuis is an important pest in sugarcane in Brazil, where alternative control methods are necessary due to cancellations of chemical pesticide registrations. Experiments were conducted to determine the pathogenicity, virulence and mass production yields of Beaweria spp. isolates as potential microbial control candidates for H . tenuis. Results demonstrated that the average virulence of the B. brongniartii isolates was comparable to that of B. hussiunu isolates. Isolates obtained from soil were as effective as microbial control agents as those obtained directly from insect hosts. However, no B. brongniartii or soil isolate was among those best isolates selected, which included two of the three termite isolates tested. LT5" for 15 selected isolates varied between 2.91 and 4.91 days, and termite mortalities caused by these isolates were between 78.7 and 98.7% after 8 days. Significant differences were observed among these selected isolates. Conidial productions on artificial media (PDA and cooked rice) correlated well for the selected isolates. However, spore production on the termite cadavers did not correlate with production on these artificial media. The most productive isolate on cadavers (634) was 21 YO more productive than the second best isolate (447), and was also a good conidial producer on artificial media with 25% lower conidial yield than the best producer (756). The least productive isolate on cadavers or artificial medium (760) produced only 3% of production by isolate 756 on cooked rice and 45% of production on termite cadavers. Because high conidial production on cadavers is a desirable characteristic to facilitate transmission of the disease in the nest, isolate 634 was selected for further development as microbial agent for H . tenuis control.

SeleÇão de isolados do fungo entomopatogênico Beauveria bassiana (Ascomycetes: Clavicipitaceae) para o controle de Rhipicephalus (Boophilus) microplus (Acari: Ixodidae)

“…A variabilidade genética dos isolados da coleção de entomopatógenos do Instituto Biológico já foi comprovada, principalmente, quanto à virulência e patogenicidade para insetos e ácaros pragas (ALMEIDA et al, 1997;TAMAI et al, 2002. ), constituindo-se, dessa maneira, em reservatórios diversificados para estudos com enfoque na seleção de materiais que apresentem características adequadas para sua utilização em programas de controle biológico de pragas agrícolas e veterinárias.…”

“…Entre as opções de controle alternativo de carrapato, destaca-se o emprego do controle microbiano que, na área agrícola, já vem sendo utilizado há muito tempo, individualmente ou em programas de manejo integrado de pragas (ALMEIDA, 1994;ALMEIDA et al 1997;BATISTA FILHO et al, 1998;TAMAI et al, 2002;MOINO JUNIOR et al, 2002).…”

“…Estudos desenvolvidos com diversas estirpes de fungos mostraram que a variabilidade genética dos isolados, principalmente quanto a parâmetros moleculares e de patogenicidade, determinam diferenças no grau de virulência do patógeno, interferindo, dessa maneira, nos percentuais de eficiência de controle de insetos e ácaros (ALMEIDA et al, 1997;TAMAI et al, 2002;FERNANDES et al, 2006).…”

“…Levando-se em conta que a coleção do Instituto Biológico conta com grande número de isolados os quais são amplamente utilizados no combate de pragas agrícolas (ALMEIDA et al, 1997;ALMEIDA et al, 1998;MOINO JUNIOR et al, 2002;TAMAI et al, 2002) Para o desenvolvimento do experimento foi utilizada a metodologia descrita por Barci e Nogueira (2006), que permite a observação diária de indivíduos de um mesmo tratamento, pelo menos por 20 dias, sem que haja alteração significativa nos percentuais de mortalidade do grupo controle.…”

Fungal disease dynamics in insect societies: Optimal killing rates and the ambivalent effect of high social interaction rates

“…They are also used against social insects (e.g., termites Almeida et al (1997) and ants (Jaccoud et al, 1999)), which are particularly successful invasive species (Chapman and Bourke, 2001;Cremer et al, 2008) with a high economic burden (Lowe et al, 2000;Pimentel et al, 2000).…”