Relative susceptibility of different stages of Rhodinius Prolixus to the entomopathogenic Hyphomycete Beauveria Bassiana

Abstract

Laboratory bioassays were conducted to determine the relative susceptibility of eggs, 1st-, 3rd-, 5th-instar nymphs and adults of Rhodnius prolixus to one isolate of the entomopathogenic hyphomycete, Beauveria bassiana. Treatments consisted of directly spraying on insects of increasing doses of inoculum (3 x 10(2) to 3 x 10(5) conidia per cm2). Mortality due to all doses of conidia was very high in the five tested stages of the target insect. Experiments on eggs demonstrated that the fungal isolate was able to kill eggs before they hatched. Both time-mortality and dose-mortality responses showed that the susceptibility of R. prolixus varied according to its stage of development and increased with age. As a matter of fact, at the dose of 3 x 10(3) conidia per cm2, LD 50 varied between 11.2 days in 1st-instar nymphs and 6.4 days in both 5th-instar nymphs and adults. Comparison of LD50 permitted to estimate that 1st-instar nymphs were about 700-fold less susceptible than the two oldest stages.

Activity of oil-formulated Beauveria bassiana against Triatoma sordida in peridomestic areas in central Brazil

“…In the laboratory, susceptibility of R. prolixus to infection with B. bassiana declined with higher nymphal instars (Luz 1994). However, Romaña and Fargues (1992) found an elevated susceptibility of R. prolixus N3 and N5 compared to N1 to B. bassiana.…”

Potential for entomopathogenic fungi to control Triatoma dimidiata (Hemiptera: Reduviidae), a vector of Chagas disease in Mexico

“…Several experiments have documented the efficacy of entomopathogenic fungi, such as Beauveria bassiana and Metarhizium anisopliae, in the control of Chagas disease vectors under laboratory [24][25][26][27][28] and fi eld conditions [29][30][31][32] . The fi rst barrier to the penetration of contact insecticides is the insect cuticle, and an increase in the thickness of the Triatoma infestans cuticle was found to be associated with the resistance of this insect to pyrethroids.…”

Effect of formulated Metarhizium anisopliae on eggs and eclosing nymphs of Triatoma infestans

“…). When it comes to triatomine targets, the only published study confirmed ovicidal activity by B. bassiana in R. prolixus (Romaña and Fargues ). A better understanding of fungal activity, especially of promising new fungal formulations, against triatomine eggs and eventually eclosing nymphs will contribute to improve effectiveness of a mycoinsecticide against important triatomine vectors.…”