C. C. López Lastra

Laboratory evaluation of chemical-biological control of the rice weevil (Sitophilus oryzae L.) in stored grains.

The virulence of ten different fungal isolates of: Beauveria bassiana, Metarhizium anisopliae, Verticillium lecanii and Paecilomyces farinosus to the rice weevil Sitophilus oryzae was tested. A fungal mix of the most efficient isolates, B. bassiana ARSEF 5500+M. anisopliae ARSEF 2974, which caused the highest mortality, was assayed in combination with fenitrothion at a concentration lower (3 ppm) than the normal 6 ppm. Fungal inoculation of insects was done by spraying conidial suspensions of each fungus on wheat. Insecticide formulations were added by spraying wheat. Treated and untreated insects were incubated on durum wheat. Insects were kept in a climatized chamber for 30 days. Observations were performed at 7, 14 and 30 days to record insect mortality. Highly significant differences were demonstrated for B. bassiana 5500 and 5501 and for M. anisopliae 2974. The level of mortality produced by treatments was: 6 ppm insecticide=97.50%, B. bassiana ARSEF 5500+M. anisopliae ARSEF 2974+3 ppm insecticide=74.17%, B. bassiana ARSEF 5500+M.anisopliae ARSEF 2974=50% and 3 ppm insecticide=37.50%. There was a statistically significant difference (p<0.05) among treatments.

Histopathology Caused by the Entomopathogenic Fungi, Beauveria bassiana and Metarhizium anisopliae, in the Adult Planthopper, Peregrinus maidis, a Maize Virus Vector

Abstract The planthopper Peregrinus maidis (Ashmead) (Hemiptera: Delphacidae) is an important vector of maize viruses in tropical and subtropical areas. Planthoppers are biologically controlled with several species of entomopathogenic fungi that have been isolated from these insect pests of rice in Asia. Beauveria bassiana (Balsamo-Crivelli) Vuillemin and Metarhizium anisopliae (Metschnikoff) Sorokin (Hypocreales: Clavicipitaceae) appear to be the most useful against planthoppers because of their ease of mass production, storage, virulence, and application. In the present study, adults of P. maidis infected with B. bassiana and M. anisopliae were observed under light and scanning electron microscopy to characterize morphologically the process of infection and the development of these fungi, prior to and after the death of the host. The hydrophobic conidia of both fungal species were able to attach to all body regions, with a preference for surfaces containing hairs. Few germinated conidia were observed on the insects body surface at 24, 48, and 72 hr post-inoculation. On the cuticular surface of P. maidis treated with B. bassiana and M. anisopliae, bacillus-like bacteria were observed. These microorganisms could be interacting with fungal conidia, playing a role of antibiosis that will not allow the fungal pathogens to germinate and penetrate. In the colonization events observed in this study, the formation and multiplication of hyphal bodies by both fungal species inside the hosts body was noted. The hosts whole body was invaded by hyphae between five and six days post-inoculation, and body fat was the most affected tissue.

Host range and specificity of an Argentinean isolate of the aquatic fungus Leptolegnia chapmanii (Oomycetes: Saprolegniales), a pathogen of mosquito larvae (Diptera: Culicidae)

An isolate from Argentina of the fungal mosquito pathogen Leptolegnia chapmanii (ARSEF 5499), was tested against 12 species of mosquito larvae and on species of non-target aquatic invertebrates and vertebrates. The mosquito species tested were Aedes aegypti, Anopheles sp., Culex apicinus, Cx. castroi, Cx. dolosus, Cx. pipiens, Cx. renatoi, Isostomyia paranensis, Ochlerotatus albifasciatus, Oc. crinifer, Psorophora cyanescens, and P. ferox. Mosquito larvae of 10 species were susceptible, with mortality rates from 10–100%. Two mosquito species Cx. renatoi and I. paranensis were not infected by Leptolegnia. None of the non-target fauna treated was infected by L. chapmanii with exception of members of the Family Chironomidae which were susceptible at low infection rates.

Isolation of Beauveria bassiana (Bals.) Vuill. (Deuteromycotina: Hyphomycetes) from the Chagas disease vector, Triatoma infestans (Hemiptera: Reduviidae) in Argentina.

A survey for natural entomopathogenic fungi of the Chagas disease vector Triatoma infestans was conducted in five provinces of Argentina since 2001. Nymphs (1.5%) and adults (3.3%) infected with a strain of the fungus Beauveria bassiana were found at Dean Funes, Córdoba province, Argentina. Field collected insects that died in the laboratory were maintained in moist chambers and incubated at 22 °C. Beauveria bassiana from infected insects was cultured on SDAY media. Pathogenicity tests were conducted with a conidial suspension (1 × 107 conidia/ml) of this isolate on T. infestans adults. A mortality rate of 100% was obtained at 15 days post-infection. This is the first record of natural infection of T. infestans by B. bassiana.

Pathogenic fungi of planthoppers associated with rice crops in Argentina

We conducted a survey of pathogenic fungi of planthoppers associated with rice crops in Los Hornos, Buenos Aires, Argentina, and a study of the seasonality and prevalence of these pathogens. Samples were taken in rice for two consecutive years. The plants sampled included rice Oryza sativa L. (Poaceae) and its surrounding weeds. The planthopper Oliarus dimidiatus Berg. (Hemiptera: Fulgoromorpha: Cixiidae) was the most abundant species associated with rice. Two species of entomophthoralean and one species of hypocrealean fungi infected and killed adults of O. dimidiatus in the rice agroecosystem. The fungi were identified as: Pandora sp. (Entomophthorales: Entomophthoraceae), Conidiobolus coronatus (Costantin) Batko (Entomophthorales: Ancylistaceae), and Beauveria bassiana (Balsamo-Crivelli) Vuillemin (Hypocreales: Clavicipitaceae). Pandora sp. was the most predominant pathogen collected. It was recorded from the middle of February to the middle of April 2005, and not found again until the end of March 2006. The report of Pandora sp., C. coronatus and B. bassiana represents the first records of these fungi as pathogens of hoppers associated with rice crops in Argentina.

Susceptibility of Adults of the Cerambycid Beetle Hedypathes betulinus to the Entomopathogenic Fungi Beauveria bassiana, Metarhizium anisopliae, and Purpureocillium Lilacinum

Abstract The cerambycid beetle Hedypathes betulinus (Klug) (Coleoptera: Cerambycidae) causes severe damage to yerba mate plants ( Ilex paraguariensis (St. Hilaire) (Aquifoliales: Aquifoliaceae)), which results in large losses of production. In this study, the pathogenicity of entomopathogenic fungi of the species Beauveria bassiana (Balsamo-Crivelli) Vuillemin (Hypocreales: Cordycipitaceae), Metarhizium anisopliae sensu lato (Metschnikoff) Sorokin (Hypocreales: Clavicipitaceae), and Purpureocillium lilacinum (Thom) Luangsa-ard, Hywel-Jones, Houbraken and Samson (Hypocreales: Ophiocordycipitaceae) on yerba mate were evaluated. Fifteen isolates of B. bassiana , two of M. anisopliae , and seven of P. lilacinum on H. betulinus adults were analyzed under laboratory conditions. The raw mortality rate caused by B. bassiana isolates varied from 51.1 to 86.3%, and their LT 50 values varied between 8.7 and 13.6 d. The isolates of M. anisopliae caused 69.6‒81.8% mortality, and their LT 50 values varied between 7.4 and 7.9 d. In contrast, isolates of P. lilacinum were not pathogenic. M. anisopliae and B. bassiana isolates were pathogenic against H. betulinus adults, suggesting that they may be useful in biological control programs for insect pests of yerba mate.

Leptolegnia chapmanii (Straminipila: Peronosporomycetes) as a future biorational tool for the control of Aedes aegypti (L.)

The aim of the present review is to summarize the current knowledge about Leptolegnia chapmanii as a pathogen of mosquito larvae. To this end, we present data on its identification, distribution, host range and effects on non-target organisms, effects of environmental factors, in vitro growth, release and persistence in anthropic environments, and effect combined with other insecticides. The data presented allow confirming its potential as a biocontrol agent.

Prevalence of entomophthoralean fungi (Entomophthoromycota) of aphids (Hemiptera: Aphididae) on solanaceous crops in Argentina

Solanum melongena L. and Capsicum annuum L. were sampled in Argentina to determine the prevalence of fungal diseased aphids. The pathogens identified were Pandora neoaphidis (Remaudière & Hennebert) Humber and Zoophthora radicans (Brefeld) Batko (Entomophthorales: Entomophthoraceae) on aphids from eggplants; and P. neoaphidis and Entomophthora planchoniana Cornu (Entomophthorales: Entomophthoraceae) on aphids from peppers. The highest fungal prevalence was 45.5% (n=2296) and 98.1% (n=3212) from aphids on eggplants and peppers, respectively. In both crops, significant differences were found on number of infected aphids among developmental stages. P.neoaphidis and E. planchoniana caused epizootics in M. persicae.

Potential plant–aphid–fungal associations aiding conservation biological control of cereal aphids in Argentina

The overall aim of this study was to identify potential associations between aphids and plants as reservoirs of entomophthoralean fungi. A survey of weeds associated with wheat field borders in two different localities was performed over two years, from April 2010 to April 2012 in the Pampeana central region, Argentina. On each sampling date, five individuals of each plant species were randomly selected, and healthy and infected aphids were collected and quantified once a month. The taxonomic identities of both aphid hosts and entomophthoralean fungi were established. Aphid–fungus associations identified as favorable for inclusion in conservation biological control strategies in borders of wheat crops are the following: Sonchus oleraceus (L.)/Hyperomyzus carduellinus (Theobald), Uroleucon sonchi (L.)/Pandora neoaphidis (Remaudière & Hennebert) Humber; S. oleraceus (L.)/H. carduellinus (Theobald)/Zoophthora radicans (Brefeld) Batko; Lamium amplexicaule (L.)/Cryptomyzus korschelti Bôrner/P. neoaphidis, Z. radicans, Entomophthora planchoniana Cornu; Foeniculum vulgare (Miller)/Dysaphis apiifolia (Theobald)/Z. radicans; Morrenia brachystephana Griseb/Aphis nerii Boyer de Fonscolombe/P. neoaphidis and Brassica rapa L./Brevicoryne brassicae (L.)/P. neoaphidis.