Relay cropping cauliflower with lettuce as a means to manage first-generation cabbage maggot (Diptera: Anthomyiidae) and minimize cauliflower yield loss

Abstract

First-generation cabbage maggot, Delia radicum (L.) (Diptera: Anthomyiidae), can cause extensive damage to newly transplanted brassica crops. This study investigated the use of relay cropping, a form of intercropping that involves overlapping two crops in the same field for a short period, as a means to 1) reduce first-generation D. radicum egg numbers by disrupting female host finding and 2) minimize yield loss by reducing the time that crops overlap. Because of the high incidence of two other Delia species, Delia platura (Meigen) and Delia florikga (Zetterstedt), treatment effects on these insects also were considered. In both years of the study (2003 and 2004), there were fewer D. radicum eggs collected from the base of cauliflower, Brassica oleracea variety botrytis, plants relay cropped with lettuce, Lactuca sativa L., than in monoculture. D. platura/D. florikga also laid fewer eggs on cauliflower in the relay crop than in monoculture in 2003, but in 2004 the opposite was true, there were more D. platura/D. florikga eggs laid on the relay-cropped cauliflower. After peak D. radicum oviposition, the lettuce was harvested. Cauliflower curd weights and diameters were comparable between treatments in both years. Plant loss because of D. platura/D. florikga feeding in the 2004 relay-cropped plots resulted in reduced yields in these plots compared with the monoculture. Although further investigation is needed into the effects of relay cropping on other pests within this system, this is the first study to demonstrate that relay cropping can reduce egg laying by D. radicum at the scale studied while minimizing competition between component crops for key resources.