Luis Francisco Angeli Alves

Seleção de isolados de Beauveria bassiana (Bals.) Vuill. e Metarhizium anisopliae (Metsch.) Sorok. contra o cascudinho Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae)

This study was carried out to evaluate entomopathogenic fungi isolates as microbial control agents of the lesser mealworm, Alphitobius diaperinus (Panzer). Larvae and adults were inoculated with conidial suspension of 99 isolates of Beauveria bassiana (Bals.) Vuill. and Metarhizium anisopliae (Metsch.) Sorok. (105 to 109 conidia/ml). Vegetative growth on culture media and sporulation on culture media, cooked rice and lesser mealworm cadavers were also evaluated. Isolates of B. bassiana were more effective than the M. anisopliae isolates and larvae were more susceptible than adults. The isolates UNIOESTE 04 and UNIOESTE 02 were originally obtained from adults of the lesser mealworm and were the most efficient isolates. In addition, UNIOESTE 04 showed high level of sporulation on different culture media and is considered a potential useful tool to lesser mealworm control.

Ocorrência natural de Beauveria bassiana (Bals.) Vuilleman (Moniliales: Moniliaceae) sobre o cascudinho, Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae), em aviário comercial de Cascavel, PR

One of the main problems in poultry houses in Brazil is the lesser mealworm, Alphitobius diaperinus Panzer. This insect inhabits the litter, manure and soil of poultry houses, feeding on bird manure, cadavers and spilt feed. The lesser mealworm serves as a reservoir of many animal pathogens. Chickens also feed readily on the beetles in infested litter and this sometimes causes nutritional problems and affects weight gain. Current control measures are generally unsatisfactory and microbial control may be a promising strategy to control A. diaperinus. Natural occurrence of entomopathogens is very important for the natural control of insect pests and this paper records the occurrence of Beauveria bassiana (Bals.) Vuill. on the lesser mealworm in commercial poultry houses, in Brazil. The evaluation was carried out weekly for six months (September/2002 to February/2003). The soil around the poultry house was collected and transferred to Zoology Laboratory from Unioeste, at Cascavel, PR. Infected larvae and adults were always present, but infected pupae were registered twice. Larvae were more susceptible than pupae and adults (incidence ranging from 49% to 100%, mean 74%, 33% to 50%, mean 6.9%; 0.9% to 100%, mean 40.7%, respectively). The pathogenicity of the fungus was confirmed under laboratory conditions following procedures outlined in Kochs postulates.

Efeito da temperatura e cama do aviário na virulência de Beauveria bassiana (Bals.) Vuill. e Metarhizium anisopliae (Metsch.) para o controle do cascudinho (Alphitobius diaperinus) (Panzer) (Coleoptera: Tenebrionidae)

This study was carried out to evaluate the influence of temperature and poultry litter on germination vegetative growth virulence and conidial production of Beauveria bassiana (Bals.) Vuill. and Metarhizium anisopliae (Metsch.) isolates on larvae and adults of the lesser mealworm (Alphitobius diaperinus) (Panzer). The vegetative growth and conidial production were evaluated on culture media. Virulence was studied submerging larvae and adults in a conidial suspension (1 x 108 conidia/ml). All the experiments were carried out in growth chamber (26oC and 32oC and 14h photophase). Fungus-killed insects were daily collected and used for microscopic conidial counts. The poultry litter effect was evaluated by submerging the insects in a fungal suspension (108 conidia/ml) and then transferring them to cups containing poultry litter (new and used). B. bassiana isolates were more sensitive than M. anisopliae to high temperature because conidia viability, vegetative growth and virulence were negatively affected (P < 0,05). The conidial production was higher to B. bassiana in 26oC (7 to 11 x 108 conidia/larval cadaver and 8 x 108 conidia/adult cadaver) (P < 0,05). Larval stage was about 10 times more sensitive to M. anisopliae at 26oC than adults stage. Regarding B. bassiana, differences on sensitivity between larval stages and adults were not observed at this temperature. However, at 32oC, larval stage was more sensitive for CB116 and UEL50 isolates. Mortality was higher when larvae and adults (15.7 and 66.7% respectively) were treated by B. bassiana and maintained on new poultry litter at 26oC) (P < 0,05).

Ocorrência de Metarhizium anisopliae (Metsch.) Sorok. em adultos de cascudinho (Alphitobius diaperinus) (Panzer) (Coleoptera: Tenebrionidae) em aviários comerciais em Cascavel, PR

Alphitobius diaperinus (Panzer), the lesser mealworm, is the most important pest in large-scale poultry production and is capable of harboring several types of poultry pathogens. Chickens feed readily on the beetles in infested litter and this sometimes causes nutritional problems and the weight gain may be affected. Chemical insecticides are usually applied, however beetle infestation are very difficult to control using these products. Besides, this control method can also offer risks to chicken and man. Microbial control may be a promising strategy to control A. diaperinus in poultry houses and natural occurrence of entomopathogenic fungi is very important to control the lesser mealworm in poultry houses. The objective of this work was to register the occurrence of Metarhizium anisopliae on adults of the lesser mealworm in commercial poultry houses in Brazil.

Selectivity of Beauveria bassiana and Metarhizium anisopliae to Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae)

Trichogramma pretiosum Riley and the entomopathogenic fungi Beauveria bassiana and Metarhizium anisopliae are efficient biological control agents and are thought to be used jointly. In here, we investigated if these entomopathogens could have any side-effects on T. pretiosum. Therefore, 1 x 8 cards containing sterilized eggs of Anagasta kuehniella (Zeller) that were sprayed with 0.2 ml of B. bassiana or M. anisopliae (1.0 x 10(9) conidia/ml) were offered to a T. pretiosum female for 24h (30 cards/fungus = 30 replicates). Afterwards, females were isolated in glass tubes. The control group was sprayed with sterile distillated water + Tween 80 (0.01%). In addition, 60 cards with sterilized eggs of A. kuehniella were submitted to parasitism by females of T. pretiosum for 24h. Of these cards, 30 were sprayed with B. bassiana or M. anisopliae and 30 with distillated water + Tween 80 (0.01%), and observed daily until parasitoid emergence. Metarhizium anisopliae decreased parasitoid emergence and caused confirmed mortality. Therefore, field and semi-field experiments should be conducted for a final assessment of the side-effects of these entomopathogens on Trichogramma as a ways to develop a control strategy in which both can be used.

Suscetibilidade de Oligonychus yothersi (Acari: Tetranychidae) ao fungo Beauveria bassiana

The Paraguay tea (Ilex paraguariensis) crop is an important economical activity in Southern Brazil. With the increase of tea consumption in the 80s, the number of monoculture crops also increased, creating favorable conditions for the development of phytophagous insect and mite populations, such as the red mite Oligonychus yothersi. The objective of this study was to evaluate the susceptibility of the red mite O. yothersi to the several strains of the Beauveria bassiana fungus. The experiments were carried out in Cascavel, PR, Brazil. Leaf disks of Paraguay tea (2.2 cm2) were previously infested with 20 adult females. Five disks were inoculated with 1 mL of each conidial suspension of B. bassiana strains (1x108 conidia per mL). Disks were kept afloat on distilled water in plastic boxes (3 cm diameter), under controlled conditions. Dead mites were transferred to a humid chamber on a daily basis to confirm the mortalities rate by the fungus. All the strains were pathogenic, with total mortality varying from 77 to 98%, 6 days after application. It was not possible to differentiate virulence levels between strains (P<0.05) by total mortality. However, confirmed mortality varied from 19 to 75%, 8 days after application, allowing for a differentiation in virulence levels between strains (P<0.05). This study concluded that the O. yothersi red mite is susceptible, at different levels, to B. bassiana tested strains.

Patogenicidade de Steinernema glaseri e S. carpocapsae (Nematoda: Rhabdita) contra o cascudinho, Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae)

The lesser mealworm, Alphitobius diaperinus (Panzer), is an important pest in poultry production systems. Due to the lack of effective and safe tactics to control this insect the interest on developing alternative control tactics such as microbial control has increased. The pathogenicity of entomopathogenic nematodes (Steinernematidae) was evaluated in laboratory conditions, against larvae and adults of the lesser mealworm. Adults were less susceptible than larvae and two strains of S. carpocapsae were the most pathogenic.

Fatores que afetam a eficiência da Terra de Diatomácea no controle de adultos de Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae)

Diatomaceous earth (DE) is a potential alternative to control the lesser mealworm of poultry farms Alphitobius diaperinus (Panzer). Our study aimed to understand the role of some of the environmental and insect behavioral factors play on DE effectiveness, such as the substrate (chicken food and poultry house litter), temperature and DE repellent activity on lesser mealworm adults. Mortality was higher at the highest temperature (32oC), and it increased with DE concentration (53 and 84% respectively, for concentrations of 86 and 172 g/m2) (P < 0.05). The substrate also influenced DE effectiveness: 95% mortality was observed in the feed, against 4% in the poultry litter. Part of these results can be attributed to the removal of DE particles by the poultry bedding, as supported by scanning electron microscopy (SEM) observations and rhodamine concentration on the surface of the insects. As to insect behavior, DE had a repellent effect, since trap capture decreased nearly 50% in traps containing DE as opposed to those containing only food. Therefore, environmental factors do affect the DE effectiveness, and they must be taken into consideration when looking into developing control strategies in the field.

Seleção de fungos entomopatogênicos para o controle de Oligonychus yothersi (McGregor) (Acari: Tetranychidae), na cultura da erva-mate (Ilex paraguariensis St. Hill.)

The virulence of strains of the entomopathogenic fungi Beauveria bassiana, Metarhizium anisopliae and Paecilomyces fumosoroseus was evaluated on Oligonychus yothersi (McGregor) in laboratory. The bioassays for strain selection and determination of LD50 and LT50 were elaborated with leaf disks of Paraguay tea infested with 10 adult females of the mite. Groups of five disks were sprayed with 1 ml of the suspension standardized in 1.0x107 conidia per ml (50 mites per treatment) of each strain. After that, the disks were maintained floating in distilled water in plastic boxes (3 cm diameter and 1.5 cm height), in environmental chamber (temperature: 25 ± 1oC; RH: 71 ± 10% and 12h photophase). Five days after the inoculation the total mortality was evaluated, and the dead mites were transferred to humid chamber. Six days after death, the sporulation in the cadavers was examined under an optical microscope. B. bassiana presented great potential as a microbial control agent, and can be incorporated in integrated pest management of the Paraguay tea red mite, O. yothersi. The B. bassiana strains UEL02, UEL08, UEL10, UEL50, CG082, CG166, CG375, CG424 and CG481, were the most virulent, with corrected and confirmed mortality higher than 70% and estimated value of CL50 varying between 1.9x106 and 6.0x107 conidia per ml and TL50 varying between 3.3 and 4.3 days.

Plano de amostragem presença-ausência para Oligonychus yothersi (McGregor) (Acari: Tetranychidae) na cultura da erva-mate

Mite infestations to the culture of mate-tea frequently causes losses by the premature fall of the leaves. So, it is necessary to monitor the population of these arthropods, and to adopt management strategies for their control. The objective of this research was to evaluate the trustworthiness of presence-absence sampling for Oligonychus yothersi (McGregor) on mate-tea orchard. This study was conducted in Cascavel, Paraná State, from April 2001 to July 2000, in a mate-tea tree commercial plantation. Biweekly sampling of 240 leaves were collected in different parts of 10 plants, and the number of mites was counted. The aggregation pattern was determined through the coefficients a and b of Taylors power law. The proportion of infested leaves and the number of required samples were estimated through mathematical model. The mite O. yothersi presented aggregate distribution. The proportion of infested leaves calculated by means of mathematical model showed to be a trustworthy parameter to estimate the population density of the mite. The number of required samples was small, making feasible the practical application of the presence-absence sampling method for O. yothersi in the culture of mate-tea.