Threshold Concentrations of Nucleopolyhedrovirus in Soil to Initiate Infections in Heliothis virescens on Cotton Plants

• Published in: Microbial ecology 2008-04, Vol.55 (3), p.530-539
• Main Author: Fuxa, James R
• Format: Article
• Language: English
• Subjects: Agricultural soils; Agrology; Animals; Bioassay; Bioassays; Biological and medical sciences; Biological control; Biomedical and Life Sciences; Clay; Cotton; Ecology; Forest soils; Fundamental and applied biological sciences. Psychology; Geoecology/Natural Processes; Gossypium - virology; Greenhouses; Growing season; Heliothis virescens; Larva - virology; Larvae; Life Sciences; Microbial Ecology; Microbiology; Mortality; Moths - growth & development; Moths - virology; Nature Conservation; Nuclear polyhedrosis virus; Nucleopolyhedrovirus - pathogenicity; Original Article; Pest Control, Biological; Plant Diseases - virology; Plants; Rain; Risk assessment; Sand soils; Sandy soils; Soil biology; Soil insects; Soil Microbiology; Soil surfaces; Soil treatment; Water Quality/Water Pollution; Wind
• ISSN: 0095-3628; 1432-184X
• DOI: 10.1007/s00248-007-9298-y

The purpose of the research was to determine threshold concentrations of nucleopolyhedrovirus (NPV) in soil for abiotic transport to cotton plants in the field and under conducive and nonconducive conditions in the greenhouse. Under the assumption that 2% mortality would suffice to initiate foci of infection in Heliothis virescens larvae on the plants, thresholds ranged from 25 to 2,311 viral occlusion bodies (OB)/g soil in the greenhouse. Thresholds generally were smaller for rain on sandy soil and wind on clay soil than for wind on sand or rain on clay. Thresholds generally increased with height of the plant above the soil surface. In field plots, percentage mortality in bioassays of cotton plants was greatest on leaves versus other tissues, and mortality increased with soil dosage and decreased with plant height and over time. Season-long soil-NPV-transport thresholds for 2% plant-bioassay mortality of larvae ranged from 1 OB/g to 7.4 x 10⁸ OB/g soil based on the amounts of NPV applied to the soil at planting time, and they ranged from 8 OB/g to 1.2 x 10⁵ OB/g soil based on bioassays of soil samples collected concurrently with plant samples throughout the growing season. These results should contribute to NPV epizootiology, biological control, and risk assessment through better understanding of viral soil-to-plant transport.