Performance of Metarhizium rileyi Nm017: nutritional supplementation to improve production and quality conidia.

This study aimed to analyze the effect of nutritional supplements on improving conidia production of Metarhizium rileyi Nm017 at laboratory scale (yields of conidia/substrate and biomass/substrate, and substrate consumption). Also, the influence on quality parameters were evaluated (germination at 36 and 48 h, enzymatic activity, and insecticidal activity on Helicoverpa zea). Six treatments (T1-T6) were assessed and all of them reached maximum conidia concentration after 7 days fermentation, a feasible production timetable. Yields from treatment T6 (yeast extract + V8 juice) were 1.5-threefold higher than the other treatments. Conidia from T6 reached germinations of 56% and 12% at 36 and 48 h, respectively, higher than T1 (without supplements), which had the lowest values found. M. rileyi conidia obtained from treatment T6 had the highest enzymatic activity (0.45 U chitinase g-1, 0.28 U lipase g-1, and 1.29 U protease g-1). However, treatments with the highest conidia yields and enzymatic activity were not positively correlated to the efficacy against H. zea. When M. rileyi was produced on T5 (yeast hydrolysate + V8 juice), conidia were 35% more virulent than treatment T6. The findings evidenced the noticeable impact of nutritional substrate amended for conidia production and quality. This work showed the relevance of insecticidal activity assessment as a selection criterion in the mass production development of a biocontrol agent.

Assessment of a potential bioproduct for controlling Cerotoma arcuata tingomariana (coleoptera: Chrysomelidae).

AIMS: The leaf-feeding pest Cerotoma arcuata tingomariana (Bechyné) (Coleoptera: Chrysomelidae) produces huge economic losses in different crops. This study aimed to produce conidia by semisolid-state fermentation and to establish the insecticidal activity of two formulation prototypes based on a native Beauveria bassiana isolate for controlling this pest. METHODS AND RESULTS: A novel fabric-based semisolid-state fermentation strategy for quick and large-scale conidia production was performed and characterized. Conidia were formulated as an emulsifiable concentrate (EC) and a water-dispersible granulate (WG). Afterwards, the mortality of C. a. tingomariana adults was assessed. A conidia concentration of 2.9 × 109 conidia cm-2 was obtained after 9 days-course fermentation and a yield of 33.4 g kg-1 dry-substrate. CONCLUSIONS: The polyester fabric-based fermentation is an efficient technique for producing and collecting B. bassiana spores. Regarding LC90 , the potency analysis showed that the EC was 21-fold more potent than the non-formulated conidia, and ~ 2.6-fold more potent than the WG. SIGNIFICANCE AND IMPACT OF STUDY: A high throughput fermentation based on polyester fabric as support for B. bassiana conidia production and subsequent formulation as an EC comprises a promising strategy for obtaining a bioproduct to control adults of C. a. tingomariana and other Chrysomelidae pests.

Formulation Process Analysis of a Virus-based Biopesticide to Control the Tomato leafminer Tuta absoluta

Abstract: Virus-based biopesticides are effective biocontrol agents of crop insect pests. Development of suitable formulations and production processes are necessary to obtain high-quality products easily adopted by farmers. A detailed unit operation study was carried out for the production process of a Phthorimaea operculella granulovirus-based biopesticide to control the tomato leafminer, Tuta absoluta, one of the most important pests affecting this crop. Physicochemical, microbiological, and insecticidal parameters were implemented in the process and applied to the finished product, and a scaling strategy was developed. A Quantitative Polymerase Chain Reaction (Q-PCR) technique was implemented to quantify viral concentrations in the active ingredient (5.34 ± 1.44 x109 Occlusion Bodies mL-1) and in the finished product (>1.6x109 OB mL-1), without contaminant interferences. The Q-PCR methodology was also useful to select the appropriate solid mixing time following Lacey´s mixing index (8 min). Factors and similarity principles influencing the liquid mixing process were identified in the scaling evaluation. Furthermore, the drying kinetics analysis enabled identifying a drying temperature of 35 °C, with an efficacy under controlled conditions higher than 97%. Contaminant concentration was lower than 1%, indicating controlled and aseptic formulation process conditions. A simple statistical method was used to estimate the reproducibility and repeatability of the parameters assessed in the finished product. These results enable to establish and extrapolate important parameters in the standardization, scale-up, and quality control for the granulovirus-based biopesticide.