Pedro Manuel Oliveira Janeiro Neves

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.

External development of the entomopathogenic fungi Beauveria bassiana and Metarhizium anisopliae in the subterranean termite Heterotermes tenuis

The subterranean termite Heterotermes tenuis is one of the main pests of sugarcane and eucalyptus in Brazil, and the use of entomopathogenic fungi, alone or associated to chemicals, is an efficient and environmentally favorable method for its control. Studies related to the fungal development on these insects are important due to the effect of insect behavior on entomopathogens. The objective of this work was to describe the external development of Beauveria bassiana and Metarhizium anisopliae on H. tenuis using Scanning Electron Microscopy (SEM), determining the duration of the different phases of fungal infection. Two fixation techniques for preparing SEM samples were also evaluated. Worker specimens of H. tenuis were inoculated with a 1 x 109 conidia mL -1 suspension of the fungi and maintained at 25±1 o C and 70±10% relative humidity. Insects were collected from 0 to 144 hours after inoculation and prepared on SEM stubs for each of the two fixation techniques. The results obtained with the two techniques were compared and duration of the different phases of the infection process were estimated from SEM observations and compared for three fungal isolates. B. bassiana and M. anisopliae have similar development cycles on the termite, but some important differences exist. The penetration, colonization and conidiogenesis phases are relatively faster for M. anisopliae than for B. bassiana, which results in a faster rate of insect mortality. The fixation technique with OsO 4 vapor is suitable for preparation of insects to be used in SEM observation of the developmental stages

PATOGENICIDADE DE BEAUVERIA BASSIANA (BALS.) VUILL. AO ÁCARO Tetranychus urticae KOCH

The pathogenicity of Beauveria bassiana (Bals.) Vuill. for Tetranychus urticae Koch was studied at 25 ± 2oC, 70 ± 5% RH and 12 h photophase, using recently emerged females. Mites were maintained for 6 days on leaf disks of Canavalia ensiformis (L.) DC. inoculated with B. bassiana, isolate 447, at concentrations of 5x106, 1x107, 5x107, 1x108, 5x108 and 1x109 conidia/ml. Progressively higher values of accumulated mortality (total, corrected and confirmed) were observed with increasing concentrations of conidia. At all concentrations, corrected mortality was lower than 50% on the sixth day. Total mortality higher than 50% was observed only at concentration of 1x109 conidia/ml.

ASSOCIATED CONTROL OF Cornitermes cumulans (KOLLAR, 1832) (ISOPTERA: TERMITIDAE) WITH Metarhizium anisopliae, Beauveria bassiana AND IMIDACLOPRID

The objective of this study was to investigate, under field conditions, the control efficiency against nests of Cornitermes cumulans using imidacoprid associated with entomopathogenic fungi (Metarhizium anisopliae and Beauveria bassiana). Field experiments were conducted to determine the minimal conidia and imidacloprid concentration jointly applied, necessary to control termite nest, but when applied separately was not efficient. This occurred when 500 mg of conidia of the pathogen (M. anisopliae or B. bassiana) were mixed with 1.9 mg of imidacloprid (Gaucho 70 PM) and 6 g of the inert calcene. It was possible to reduce the conidial concentration 4 times and the insecticide 157 times in relation to the concentrations usually recommended. These concentrations allowed high levels of control (> 80%) of big nests and a considerable reduction in control cost. In addition, it is important to consider the ecological benefits provided by this association using reduced quantities of the chemical insecticide. Thus, this strategy should be exploited as an important alternative in the control of C. cumulans big colonies.

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.

Selectivity of Organic Products to Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae).

The selectivity of various entomopathogens and one insecticide (chlorpyrifos = positive control) to Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) was evaluated in the laboratory, using the protocol established by the Working Group on “Pesticides and Beneficial Organisms” of the IOBC. The evaluated parameters were parasitism (%), adult emergence (%), and product repellency to the parasitoid when sprayed on host eggs prior to parasitism (free-choice and no-choice tests). Most of the studied entomopathogens (Bacillus thuringiensis var. kurstaki, Bacillus thuringiensis var. aizawai, Beauveria bassiana, Metarhizium anisopliae, and Trichoderma harzianum) had no effects on biological parameters and were classified as harmless to T. pretiosum. Emergence of parasitoids (progeny viability) was reduced, but remained above 90%, when host eggs were sprayed with Baculovirus anticarsia prior to parasitism in the free-choice test, and B. anticarsia was therefore considered harmless. Chlorpyrifos (positive control) caused high adult parasitoid mortality in all bioassays. While T. pretiosum and the tested entomopathogens may be used simultaneously in integrated pest management programs, the use of chlorpyrifos should be avoided.

In vitro sensitivity of antagonistic Trichoderma atroviride to herbicides

Trichoderma atroviride was tested in vitro for its sensitivity to different herbicides. The dosages tested were recommended dosage (RD), half dosage (½RD), and double dosage (2RD). Germination, colony-forming units (CFU), radial growth, and spore production were evaluated. Carfentrazone-ethyl and sulfentrazone inhibited the germination at RD and 2RD. A reduction in the CFU was observed for glufosinate-ammonium, atrazine, carfentrazone-ethyl, diuron + paraquat dichloride, imazapyr, oxyfluorfen, and sulfentrazone at each of the tested dosages. Radial growth was influenced by ametryn, atrazine, carfentrazone-ethyl, oxyfluorfen, and sulfentrazone herbicides, with an 80% reduction of the colonial area. Spore production was affected by carfentrazone-ethyl, oxyfluorfen, and sulfentrazone with colonial area reductions of over 70%. It was concluded that 2,4 D, clomazone, and imazapyr herbicides showed the least toxicity to T. atroviride and should be used in the crops where the fungus has been applied for phytopathogen control.

Biology of Spodoptera eridania and Spodoptera cosmioides (Lepidoptera: Noctuidae) on different host plants

Abstract The moths Spodoptera eridania (Stoll) and Spodoptera cosmioides (Walker) are pests of increasing importance in various grain production systems, causing defoliation and damage to reproductive structures of plants. This fact underscores the need for studies that analyze the nutrition and development of pests on different hosts. The objective of this study was to evaluate the development of S. eridania and S. cosmioides feeding on different host species. To this end, newly hatched larvae were separated individually into waxed cups and fed soybean, cotton, maize, wheat, oat leaves, or an artificial diet as control. The evaluated parameters were: duration of larval, pre-pupal, and pupal development (days), pupal weight (g), sex ratio (%), larvae-adult survival (%), oviposition preference, larval feeding performance, and weight gain on different hosts. Soybean and cotton were found to be more suitable hosts for development and oviposition of S. eridania and S. cosmioides than oat, wheat, and maize, all of which negatively affected larval development and survival. The maize cultivar ‘DKB 390’ did not allow for larvae to develop to adults and therefore proved to be inadequate for both studied Spodoptera species.