Abstract

Domestic sheep (Ovis spp.) grazing is emerging as an integrated pest management tactic for alfalfa weevil, Hypera postica (Gyllenhal), management and a degree-day model is needed as a decision and support tool. In response to this need, grazing exclosures with unique degree-days and stocking rates were established at weekly intervals in a central Montana alfalfa field during 2008 and 2009. Analyses indicate that increased stocking rates and grazing degree-days were associated with decreased crop levels of weevil larvae. Larval data collected from grazing treatments were regressed against on-site and near-site temperatures that produced the same accuracy. The near-site model was chosen to encourage producer acceptance. The regression slope differed from zero, had an r2 of 0.83, and a root mean square error of 0.2. Crop data were collected to achieve optimal weevil management with forage quality and yield. Differences were recorded in crude protein, acid and neutral detergent fibers, total digestible nutrients, and mean stage by weight. Stem heights differed with higher stocking rates and degree-days recording the shortest alfalfa canopy height at harvest. The degree-day model was validated at four sites during 2010 with a mean square prediction error of 0.74. The recommendation from this research is to stock alfalfa fields in the spring before 63 DD with rates between 251 and 583 sheep days per hectare (d/ha). Sheep should be allowed to graze to a minimum of 106 and maximum of 150 DD before removal. This model gives field entomologists a new method for implementing grazing in an integrated pest management program.

Links

Aggregator Full Text

Authors

Goosey HB

Institution

Department of Animal and Range Sciences, Montana State University, 103 Animal Bioscience Building, P.O. Box 172900, Bozeman, MT 59717, USA. hgoosey@montana.edu

Source

Journal of economic entomology 105:1 2012 Feb pg 102-12

MeSH

Agriculture
Animals
Feeding Behavior
Larva
Medicago sativa
Models, Biological
Montana
Pest Control, Biological
Regression Analysis
Seasons
Sheep, Domestic
Temperature
Weevils

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't
Validation Studies

Language

eng

PubMed ID

22420261