Short- and Long-Term Evaluation of a Fixed Dose of Beauveria bassiana Strain MS-8 Diluted in Various Doses of Kaolin as a Powder Formulation Applied to Rice Grains to Control Almond Moth, Ephestia cautella Walker (Lepidoptera: Pyralidae).

Short-term and long-term evaluation studies were conducted against Ephestia cautella on rice grains, using Beauveria bassiana Strain MS-8 formulated in various doses of kaolin as an active carrier. In the short-term study (45 days), a fixed dose of 0.03 g conidia kg-1 of grain of Strain MS-8 was formulated in kaolin at doses of 0.3, 0.5, 1, and 2 g kg-1 of grain. These formulations were evaluated for their effects on larval mortality and the number of adults emerged. The highest level of larval mortality (90.0%) and the lowest numbers of adults emerged (1.6 insect/100 g of rice grain) were caused by Strain MS-8 in a kaolin dose of 2 g kg-1. However, Strain MS-8 in a kaolin dose of 1 g kg-1 performed well for the same parameters. In the long-term evaluation study (180 days), the same dose of Strain MS-8 was formulated in kaolin at doses of 0.5, 1, 2, and 3 g kg-1 of grain. These formulations were then evaluated against the levels of webbed grain, grain damage, and weight loss. The lowest levels of webbed grain (2.0%), grain damage (3.0%), and weight loss (1.8%) were caused by Strain MS-8 in kaolin at a dose of 3 g kg-1, although Strain MS-8 in kaolin doses of 1 g and 2 g kg-1 also performed well for the same parameters. The highest levels of webbed grain (15.0%), grain damage (30.0%), and weight loss (9.0%) were observed in the untreated control treatment (UCT).

Effect of surfactants and temperature on germination and vegetative growth of Beauveria bassiana.

Three non-ionic surfactants: Tween20, Tween80 and Breakthru (®) were screened for their effects on spore germination and mycelial growth rates and for their influence on three isolates of Beauveria bassiana spore germination at various temperatures. Tween20 and Tween80 were compatible with all the B. bassiana isolates in the germination studies, but inhibited germination at higher surfactant concentrations, irrespective of the conidial concentrations . Breakthru (®) had an inhibitory effect on germination even at the lowest concentration of 0.1% on all the B. bassiana isolates. The effects of the surfactants on spore germination did not correspond with their effects on colony growth. Conidial viability within the same formulation declined significantly with increases in temperature, irrespective of the surfactant. The optimal temperature for conidial germination of B. bassiana isolates was approximately 25 °C with an upper limit at 30 °C. Isolate 7320 was identified as the least affected by the different surfactants. This isolate was able to germinate rapidly in a broad temperature range of 25-30 °C after 24 h, this characteristic being an essential factor in controlling house fly populations in poultry houses.

Effect of surfactants and temperature on germination and vegetative growth of Beauveria bassiana

Three non-ionic surfactants: Tween20, Tween80 and Breakthru® were screened for their effects on spore germination and mycelial growth rates and for their influence on three isolates of Beauveria bassiana spore germination at various temperatures. Tween20 and Tween80 were compatible with all the B. bassiana isolates in the germination studies, but inhibited germination at higher surfactant concentrations, irrespective of the conidial concentrations. Breakthru® had an inhibitory effect on germination even at the lowest concentration of 0.1% on all the B. bassiana isolates. The effects of the surfactants on spore germination did not correspond with their effects on colony growth. Conidial viability within the same formulation declined significantly with increases in temperature, irrespective of the surfactant. The optimal temperature for conidial germination of B. bassiana isolates was approximately 25 °C with an upper limit at 30 °C. Isolate 7320 was identified as the least affected by the different surfactants. This isolate was able to germinate rapidly in a broad temperature range of 25–30 °C after 24 h, this characteristic being an essential factor in controlling house fly populations in poultry houses.

In vitro effects of flutriafol and azoxystrobin on Beauvaria bassiana and its efficacy against Tetranychus urticae.

BACKGROUND: Testing the compatibility of chemical pesticides and fungal biocontrol agents is necessary if these two agents are to be applied together in the integrated management of plant pests and diseases. In this study, the fungicides azoxystrobin (a strobilurin) and flutriafol (a triazole) were tested in vitro for their effects on germination of conidia and mycelial growth of Beauveria bassiana (Bals.) Vuill. and in bioassay for their effect on fungal activity against Tetranychus urticae Koch. The fungicides were tested at three different concentrations [recommended rate for field use (1 x X) and the dilutions 10(-1)x X and 10(-2)x X]. RESULTS: Flutriafol inhibited growth of mycelia and germination of the fungal conidia at all concentrations tested in vitro, and also reduced the efficacy of B. bassiana in bioassays against mites. The inhibitive effect of azoxystrobin in vitro varied with the concentration applied. A significant effect was observed at 1 x X and 10(-1)x X concentrations on both the germination of conidia and mycelia growth. At 10(-2)x X concentration, azoxystrobin showed little effect on B. bassiana. However, when this fungicide was tested in bioassays, none of the concentrations reduced B. bassiana activity against mites. CONCLUSION: Azoxystrobin was most compatible with B. bassiana, while flutriafol was the most harmful. Further studies are required to confirm the negative effect of flutriafol on B. bassiana activity.

Effects of adjuvant and conidial concentration on the efficacy of Beauveria bassiana for the control of the two spotted spider mite, Tetranychus urticae.

Greenhouse experiments were conducted on various crops (cucumber, tomato, eggplant, green bean) to ascertain the effects of Break-thru (polyether-polymethylsiloxane-copolymer, a silicone surfactant) and an oil emulsion, on Beauveria bassiana (Balsamo) Vuillemin (Bb) applications for the control of the two spotted spider mite, Tetranychus urticae Koch. The objectives were to compare a) the efficacy of Bb control when applied in aqueous Break-thru or an oil emulsion; b) the effects of various concentrations of Bb conidia, as affected by each surfactant; and c) the effects of Break-thru on the activity of the fungus. Conidia were suspended either in an aqueous Break-thru or an emulsifiable formulation at different conidial concentrations (1.05 x 10(6), 2.1 x 10(6) and 4.2 x 10(6) conidia ml(-1)) and sprayed onto leaves 2 weeks after artificial pest inoculation. Two sprays were performed, with an interval of one week from one spray to another, and T. urticae population counts (both motile and egg stages) were made on plant leaves 7 days after each spray. Bb conidia in Break-thru((R)) were more efficacious than conidia in emulsifiable formulation. With the highest rate of conidia (4.2 x 10(6) conidia ml(-1)), mortality of adult mites ranged from 60 +/- 4.2 (mean +/- SE) to 85.7 +/- 4.3% in the Break-thru suspension and 39.4 +/- 7 to 61.3 +/- 6% in the oil emulsion. Leaf damage index was also substantially reduced from 70% in the unsprayed control to 40% by the application of Bb conidia at the highest rate with Break-thru. Break-thru can be combined with Bb in the integrated management of T. urticae and Isolate R444 is a promising candidate for the control of the pest.