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United States Department of Agriculture

Agricultural Research Service

Research Project: Biting and Stinging Pests: Ecology and Biologically-base Control

Location: Biological Control of Pests Research Unit

Title: Effects of conidial densities and spray volume of Metarhizium anisopliae and Beauveria bassiana fungal suspensions on conidial viability, droplet size and deposition coverage in bioassay using a novel bioassay spray system

Authors
item Jin, Xixuan
item Huang, Yanbo
item Thomson, Steven
item Elliott, Robert

Submitted to: Biocontrol Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 11, 2012
Publication Date: March 1, 2013
Citation: Jin, X., Huang, Y., Thomson, S.J., Elliott, R.B. 2013. Effects of conidial densities and spray volume of Metarhizium anisopliae and Beauveria bassiana fungal suspensions on conidial viability, droplet size and deposition coverage in bioassay using a novel bioassay spray system. Biocontrol Science and Technology. 23:362-366.

Interpretive Summary: An efficient and reliable laboratory bioassay system plays critical roles in biopesticide development. A novel bioassay system was recently developed to investigate the effectiveness of biocontrol agents for the control of the red imported fire ant. Studies were continued to study the conidial viability during bioassay spray with different suspensions of Metarhizium anisopliae and Beauveria bassiana, and to investigate the effects of conidial density and spray volume on the distribution of droplet size and deposit coverage using water sensitive paper (WSP) cards. Results showed that there was no adverse effect on the viability of conidia during the spray. The effects of spray volume on droplet size and coverage were significant regardless of the two tested biocontrol agents. Conidial density of tested suspensions of B. bassiana had significant effect on droplet size and the droplet coverage on the WSP cards. This is the first to report the effects of conidial density of biocontrol agents on the distribution of droplet size and coverage during bioassay studies. Natural transform provided better models for both droplet size distribution and coverage regardless fungal strains.

Technical Abstract: Experiments were conducted to study the conidial viability during bioassay spray with different suspensions of Metarhizium anisopliae ATCC 62176 and Beauveria bassiana NI8, and to investigate the effects of conidial density and spray volume on the distribution of droplet size and deposit coverage using water sensitive paper (WSP) cards. Results showed there was no adverse effect on the viability of ATCC 62176 or NI8 conidia during the spray regardless of conidial density and spray volume. The interaction between conidial density and spray volume of both fungal species had no effect on droplet size distribution expressed as Volume Median Diameter (VMD) or natural log transformed VMD (ln VMD), and had no effects on droplet coverage of both fungal strain suspensions either. The effects of spray volumes of ATCC 62176 suspensions on the distribution of droplet size and on the droplet coverage were highly significant (P < 0.0001) regardless of the natural log transform and the conidial densities. Conidial density of tested suspensions of NI8 had significant effect on ln VMD and the droplet coverage on the WSP cards (P <0.01). The effects of spray volumes of conidial suspensions of NI8 on the distribution of droplet size and droplet coverage were highly significant (P < 0.0001) regardless of the natural log transform. This is the first to report the effects of conidial density of biocontrol agents on the distribution of droplet size and coverage during bioassay studies. Natural transform provided better models for both droplet size distribution and coverage regardless fungal strains.

Last Modified: 9/23/2014