A fully developed integrated pest management (IPM) system uses all available strategies for a given pest or pest complex in a cropping system; incorporating host plant resistance, biological, cultural and physical controls and chemical control when necessary (Pedigo, 1999). Several such management strategies have been developed in alfalfa for the potato leafhopper (Empoasca fabae) (PLH). The first glandular haired varieties of alfalfa, bred for resistance to PLH were released for market in 1997. Field studies of these varieties have been met with varying levels of success. Lefko et al. (2000) observed that established resistant alfalfa stands could tolerate up to 2.5 greater the PLH pressure as a susceptible stand. However, when leafhopper pressure is low, resistant alfalfa has expressed some amount of yield drag (Hogg et al. 1998, Hansen et al. 2002). The presence of grasses in alfalfa fields has also been correlated to a reduction in PLH abundance. Degooyer et al. (1999) showed that both orchardgrass and bromegrass intercropped in alfalfa stands significantly reduced the number of PLH present, but noted it was not enough to keep populations below economic thresholds. Grasses are also promoted as an intercrop with alfalfa for the increase in digestible fibers and decrease in non-fiber carbohydrates they provide, which can help reduce incidence of ruminal acidosis (Lee, 2011).
Soil Science Extension
University of Wisconsin Madison