Intercropping with aromatic plants hindered the occurrence of Aphis citricola in an apple orchard system by shifting predator-prey abundances

Enhancing biological control of pests through habitat management in agricultural systems has gained increasing attention. Three different aromatic plants, ageratum (<i>Agerarum houstonianum</i> Mill.), French marigold (<i>Tagetes patula</i> L.) and basil (<i>Ocimum basilicum<i> L.), were chosen as intercrops for apple orchards to evaluate the effects of intercropping on <i>Aphis citricola</i> Van der Goot and its local natural enemies in China. We found that compared with natural vegetation, <i>A. citricola</i> abundance was significantly decreased by 29.26%, 35.80% and 38.28% in plots intercropped with ageratum, French marigold and basil, respectively. The number of natural enemies of <i>A. citricola</i> in plots intercropped with <i>T. patula</i> and <i>O. basilicum</i> were significantly higher than in plots of natural vegetation. Equally important, intercropping affected the composition of natural enemies and the population dynamics of <i>A. citricola</i> and its natural enemies. Annual cumulative numbers of natural enemies were significantly negatively correlated with <i>A. citricola</i> annual cumulative individual numbers except for <i>O. tantillus</i>. Our results demonstrate that intercropping with aromatic plants could be an effective method for biological control of <i>A. citricola</i> in apple orchards.</i></i>