In vitro efficacy of Metarhizium anisopliae sensu lato against unfed Amblyomma parvum (Acari: Ixodidae).

Amblyomma parvum Aragão (Acari: Ixodidae) is a tick species found with wide distribution in the Neotropical region. Even though it is a wildlife-related tick, it is also a frequent parasite of domestic animals, is aggressive to human beings and may harbor pathogenic microorganisms. Therefore, it is a target species for control on domestic animals, particularly those at the rural-wildlife interface. Herein, the efficacy of two isolates (E9 and IBCB 425) of an entomopathogenic fungus, Metarhizium anisopliae sensu lato, already evaluated for ticks that parasitize domestic animals, was tested against unfed A. parvum adults. Both isolates displayed high acaricidal efficacy after immersion in fungal conidial suspensions for 5 min. Isolate E9 killed all ticks by the 7th day post-treatment, and isolate IBCB 425 did so by the 11th day. Tick mortality of 80 and 90% was achieved as early as the 3rd and 4th days, respectively, with both treatments. Thus, if a commercial M. anisopliae s.l. acaricide against domestic animal ticks is developed, it would also be effective against A. parvum.

Mortality of Conotrachelus humeropictus in response to combined application of the nematode Steinernema brazilense and the fungus Beauveria bassiana / Mortalidade de Conotrachelus humeropictus pela aplicação combinada do nematoide Steinernema brazilense com o fungo entomopatogênico Beauveria bassiana

The fruit borer Conotrachelus humeropictus is one of the most important pests of the cupuaçu crop, and can promote yield losses of around 50%. The present study involved the selection of Beauveria bassiana isolates on Conotrachelus psidii larvae, which was used as test insect due to its taxonomic closeness to C. humeropictus. In order to assess their interaction using combined application, we studied the ability of the nematode to carry conidia of B. bassiana and Metarhizium anisopliae to soil layers. This study also aimed to establish a biological control method for cupuaçu borer with the use of the fungus B. bassiana at 10 kg/ha and the entomopathogenic nematode Steinernema brazilense at 1, 3, 9, and 27 IJ/cm2, applied as single and combined treatments. In the selection of B. bassiana strains for C. psidii, the IBCB 276 and IBCB 165 isolates were the most promising ones, causing 86 and 84% mortality, respectively. The IBCB 276 strain was applied in the field to control C. humeropictus. In the study of carriage of conidia in soil, the nematode S. brazilense was found to be capable of carrying conidia of B. bassiana to deep 7 to 10 cm soil layers. This was not observed with M. anisopliae, found only in the topsoil. In field trials against C. humeropictus larvae, B. bassiana promoted 15.6% mortality. The nematode promoted 60.0% mortality at the highest concentration used, and their combined use with B. bassiana (10 kg/ha) increased mortality to 65.6%, with an additive interaction observed between the two entomopathogens.(AU)

A broca-do-cupuaçu, Conotrachelus humeropictus, é uma das principais pragas da cultura, podendo ocasionar perdas de 50% na produção. O presente trabalho envolveu uma seleção prévia de isolados de Beauveria bassiana em larvas de Conotrachelus psidii, utilizado como inseto teste por ser próximo taxonomicamente à C. humeropictus. Com o objetivo de avaliar causa-efeitos da interação na aplicação combinada, foi estudada a capacidade do nematoide carrear conídios de B. bassiana e Metarhizium anisopliae pelas camadas de solo. O trabalho também objetivou avaliar o controle biológico da broca-do-cupuaçu, através do uso do fungo B. bassiana 10 kg/ha, e do nematoide entomopatogênico Steinernema brazilense 1, 3, 9 e 27 JI/cm2, aplicados em tratamentos isolados e em combinação. Na seleção de isolados de B. bassiana para C. psidii, os isolados IBCB 276 e IBCB 165 foram os mais promissores, causando, respectivamente, 86 e 84% de mortalidade confirmada. O isolado IBCB 276 foi aplicado em campo para controlar C. humeropictus. No estudo de carreamento de conídios, o nematoide S. brazilense foi capaz de carrear conídios de B. bassiana para a camada de 7 a 10 cm de profundidade no solo. A mesma ação não foi observada com M. anisopliae, encontrado somente na camada superficial do solo. Nos ensaios de campo contra C. humeropictus, B. bassiana promoveu 15,6% de mortalidade. O nematoide promoveu 60,0% de mortalidade na maior concentração utilizada e, na combinação dessa concentração do NEP com B. bassiana (10 kg/ha), a mortalidade atingiu 65,6%, observando-se interação aditiva entre os dois entomopatógenos.(AU)

Effect of Metarhizium anisopliae fungus on off-host Rhipicephalus (Boophilus) microplus from tick-infested pasture under cattle grazing in Brazil.

This work aimed to assess the effect of the fungus Metarhizium anisopliae on off-host Rhipicephalus (Boophilus) microplus from tick-infested Brachiaria decumbens pasture undergoing cattle grazing. For this purpose a naturally tick-infested Brachiaria decumbens pasture of 60 m × 100 m with twelve grazing Holstein Friesian-Nelore (Bos indicus) cross breed bovines was sprayed 12 times, 21 days apart with an aqueous conidial suspension of the E9 isolate of M. anisopliae fungus. Control pasture was treated with conidial suspension vehicle only. Efficacy of treatment was evaluated by tick larvae counts on the pasture and that of engorged female ticks on grazing cattle. Fungus persistence on grass stems as well as soil pasture was assessed after each spray. Efficacy of fungus against ticks was also measured by an in vitro immersion test. Whereas in vitro test showed a clear pathogenic effect of the fungus on ticks, no pathogenic effect over R. (B.) microplus ticks was detected in the field trial by spraying pasture with fungal suspension. Fungus from the suspension could be recovered from both the grass stem as well as the soil of sprayed pasture, even though the numbers obtained varied distinctly and could only be recovered shortly after spray. Pasture environments with exposure to sun and rain, seem to be very detrimental to the fungus, thus suspensions which provide fungus with protection or more resistant isolates to these should be looked for. In order to achieve high fungal efficacy against tick under field conditions, accurate laboratory assays, optimization of application strategy and knowledge of interactions between fungal strains and environmental factors are warranted.

Susceptibility of adult and larval stages of the horn fly, Haematobia irritans, to the entomopathogenic fungus Metarhizium anisopliae under field conditions.

The efficacy of M. anisopliae strain E9 as a biological insecticide for the adult and larval stages of H. irritans was assessed under field conditions. To assess larvicidal activity, nine heifers were randomly divided into three groups, which were maintained separated from each other. The first group ingested fungal spores encapsulated in alginate pellets. The second group ingested in natura spores that were grown on sterilized rice. In both groups, each animal received three meals a day, with each meal containing 2 x 10(10)conidia. The third group received no treatment and was used as a control. Fecal samples from manure and whole dung pats were collected from each of the three separate pastures on the day that the animals were allocated and on days 1, 3, 6, 9 and 12 afterwards. The fecal samples were tested for the presence of fungal colony forming units (CFU), and the emergence of horn flies was observed in the dung pats. Significantly less (P<0.01) adult horn flies were found in dung pats of the group treated with encapsulated fungi (11.7) than in those from the heifers treated with conidia in natura (27.9) or from the control group (29.5). The fecal samples of the treated animals presented significantly higher numbers of M. anisopliae CFUs then those from the untreated controls. We found that on day 9 fecal samples from animals given microencapsulated conidia had significantly higher CFUs than those from animals treated with conidia in natura. To assess adulticide activity, four heifers were sprayed with a suspension of 3 x 10(10)conidial(-1) of M. anisopliae, and four control animals were sprayed with the same solution without conidial content. Four sprayings were done at five-day intervals, and all animals were photographed daily to observe the quantity of flies present. After the second spraying, we observed an average of 22.9 flies per animal; untreated heifers had an average of 43 flies per animal; thus, the treatment significantly (P<0.05) decreases fly infestation. The results obtained from both tests show that M. anisopliae strain E9 has a pathogenic effect on H. irritans larvae in bovine manure when administered orally and on adult fly infestations when applied as a spray on the hosts.