Incidence of Pieris rapae in Organic Broccoli Grown With Living Mulches Under Floating Row Cover

Floating row covers and living mulches are two techniques that have been used individually as means of controlling the imported cabbage worm (Pieris rapae L.) in broccoli. They have, however, never been tested in combination. The present study investigated their combined use as a way to reduce P. rapae incidence in organic broccoli in 2006 and 2007. Using a combination of row cover and two different living mulches—red clover (Trifolium pratense L.) or alfalfa (Medicago sativa L.)—increased P. rapae larvae incidence in broccoli compared to use of the row cover with bare ground. When row cover and living mulches were used together, the creation of a sheltered microenvironment appeared to be a more important factor in the choice of a site for oviposition by P. rapae than plant nutrient content and chlorophyll level of plants. Use of living mulches provided better conditions for development and incidence of P. rapae larvae in organic broccoli when grown under floating row cover.