Potential of mungbean, Vigna radiatus as a trap crop for managing Apolygus lucorum (Hemiptera: Miridae) on Bt cotton

In recent years, the mirid Apolygus lucorum has become the key insect pest of Bt cotton in China. Currently, insecticide use is the sole pest management option available for most Chinese cotton farmers. As irrational pesticide use may have several undesirable effects, environmentally sound and sustainable management alternatives are urgently needed. In this paper, we evaluate the potential of mungbean, Vigna radiatus as a trap crop for A. lucorum in Bt cotton. Plant suitability trials showed that A. lucorum population densities on mungbean were significantly higher than those on cotton. Large-scale field experiments were conducted during 2006 and 2007 to determine the effectiveness of mungbean strips for managing A. lucorum in Bt cotton fields. In this experiment, 0.1 ha Bt cotton fields were established, and mungbean strips covered approximately 10% of the total area. With periodical insecticide applications in mungbean strips, average mirid population densities in cotton fields were 18.1 ± 2.1 individuals per 100 plants, versus 36.0 ± 3.4 in the fields without mungbean strips in 2006. However, A. lucorum population still surpassed economic threshold (i.e., 5, 10, and 20 individuals per 100 cotton plants at the seeding stage, the squaring and flowering stages, and the belling stage, respectively). In 2007, aside from the insecticide sprays within the mungbean strips, 2–3 insecticide applications were done in the cotton field. As a result, A. lucorum populations were kept below economic threshold, and the total amount of insecticides reduced about 70% of those used in the common chemical-controlled fields. Our work shows that mungbean has considerable potential as a trap crop in Bt cotton fields, and its adoption by Chinese farmers very likely will reduce current levels of pesticide use in this crop.