Vegetation Manipulation Impact on Predator and Prey Populations in Louisiana Sugarcane Ecosystems

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Abstract
A 3-year study on southeastern Louisiana sugarcane illustrated the beneficial impact of ground vegetation on predation enhancement. Abundance and diversity of both ground- and foliage-associated predators and prey were higher in weedy than in weed-free habitats. The red imported fire ant, Solenopsis invicta Buren, a major predator of the key insect pest, the sugarcane borer, Diatraea saccharalis (F.), was more abundant in weedy (17 mounds per hal than in weed-free (5 mounds per ha) habitats. Foraging of S. invicta, however, was slightly higher in weed-free habitats. Azinphosmethyl, commonly used for D. saccharalis control, decreased system stability through food-web route disruption; use of this chemical decreased coleopterans, phytophagous insects collectively, and spiders 51, 35, and 67%, respectively. A subcompetitive stand of annual broadleaf weeds enhanced predator populations early in the season, then died back at canopy closure, thus eliminating competition lossesto the crop. Additionally, cane and sugar yields in broadleaf habitats and returns in dollars per ha averaged 19% higher than in the weed-free habitats. Predation system stabilization through floral, and consequently faunal, diversification proved to be a judicious and economically superior approach to integrated pest management in Louisiana sugarcane.