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Agronomics and Economics of potato leafhopper (PLH)-resistant alfalfa intercropped with perennial forage grass for PLH control 2007

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Project Leaders: J. Hansen, Senior Research Associate, Plant Breeding and Genetics, Cornell University; J.K. Waldron, NYS IPM; J. Losey, Professor of Entomology, Cornell University; D. Viands, , Professor of Plant Breeding and Genetics, Cornell University ; J. Hanchar, Extension Associate, Cornell University

Cooperator: J. Cherney, Professor, Cornell University

Abstract: Potato leafhopper (PLH) is the most damaging alfalfa pest in the Northeast (NE).  Forage grasses mixed with alfalfa can cause PLH to emigrate but may reduce forage quality.  Some alfalfa cultivars have PLH-resistance, yet are not immune to PLH damage.  The objectives are to compare PLH populations and densities, and forage yield and quality of a conventional alfalfa cultivar and a PLH-resistant cultivar both in monoculture and intercropped with grass, to conduct an economic analysis, and to share results in extension outreach.  The PLH populations and forage growth were disappointingly low in 2007, in part due to drought conditions.  In spite of this, PLH damage scores indicated that the PLH-resistant cultivars have less leaflet yellowing than the conventional alfalfa cultivars, and the alfalfa-grass mixtures have less leaflet yellowing than the alfalfa monocultures.  However, at low PLH populations, these small but statistically significant differences did not translate into differences in yield between the PLH-resistant and conventional cultivars.  The alfalfa-grass mixtures were significantly higher in yield than the alfalfa monocultures.  Thus, results from one production year at one location, have shown that without insecticide treatment, PLH-resistant alfalfa planted with a forage grass could provide the highest forage yield.