Parsons C K, Dixon P L, Colbo M
Agriculture & Agri-Food Canada, P.O. Box 39088, St. John's, Newfoundland and Labrador, Canada AlE 5Y7.
J Econ Entomol. 2007 Jun;100(3):838-46. doi: 10.1603/0022-0493(2007)100[838:rccwla]2.0.co;2.
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 florilega (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. florilega 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. florilega 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. florilega 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.
第一代甘蓝蝇，即萝卜地种蝇（Delia radicum (L.)，双翅目：花蝇科），会对新移栽的十字花科作物造成广泛损害。本研究调查了接力种植的用途，接力种植是间作的一种形式，即在同一地块短时间内使两种作物重叠种植，以此来：1）通过干扰雌蝇寻找寄主来减少第一代萝卜地种蝇的产卵量；2）通过缩短作物重叠时间来尽量减少产量损失。由于另外两种地种蝇，即灰地种蝇（Delia platura (Meigen)）和葱地种蝇（Delia florilega (Zetterstedt)）的发生率较高，因此也考虑了对这些昆虫的处理效果。在研究的两年（2003年和2004年）中，从与生菜（Lactuca sativa L.）接力种植的花椰菜（Brassica oleracea variety botrytis）植株基部收集到的萝卜地种蝇卵，比单作时少。2003年，灰地种蝇/葱地种蝇在接力种植作物中的花椰菜上产卵也比单作时少，但在2004年情况相反，在接力种植的花椰菜上产的灰地种蝇/葱地种蝇卵更多。在萝卜地种蝇产卵高峰期过后，收获生菜。两年中各处理间花椰菜的花球重量和直径相当。2004年，接力种植地块中因灰地种蝇/葱地种蝇取食造成的植株损失导致这些地块的产量低于单作地块。尽管需要进一步研究接力种植对该系统中其他害虫的影响，但这是第一项证明接力种植能在所研究的规模上减少萝卜地种蝇产卵，同时尽量减少组成作物对关键资源竞争的研究。
