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An undersowing system with additional intercropping of flowering plants was assessed in field trials in Germany and Japan to estimate regulating effects on pests and possible negative effects on white cabbage (Brassica oleracea var. capitata). In particular, we tested cabbage undersown with wheat (Triticum aestivum L.) and cabbage undersown with wheat plus additional sweet alyssum (Lobularia maritima L. Desv.) intercropping. Counts of the aphid species Brevicoryne brassicae (L.) and Myzus persicae (Sulzer), as well as related predators on cabbage plants, were determined. Abundance of Phyllotreta spp. flea beetles and their feeding damage on cabbage plants were recorded and cabbage yield was compared. In both countries, trials showed that wheat undersowing reduced the abundance of M. persicae but not B. brassicae. The occurrence of natural enemies on cabbage plants was not significantly affected by any of the companion plants. Additional sweet alyssum intercropping increased the abundance of adult hoverflies at the German but not at the Japanese location. However, it also significantly increased flea beetle infestation on cabbage plants at both locations. Neither wheat undersowing nor additional sweet alyssum intercropping significantly reduced cabbage harvest weight. In conclusion, adding companion plants can be a promising method to improve pest control in vegetable crops. However, intercropping crucifer crops with sweet alyssum may not be recommended in regions where flea beetles are a relevant pest because of the observed enhancing effect on them. In contrast, to prove the positive effect of wheat undersowing on white cabbage, results from further years of investigation are needed. [ABSTRACT FROM AUTHOR]

The invasive orange spiny whitefly (OSW) Aleurocanthus spiniferus has extended its distribution to non-native areas since the early 20th century. In a similar manner, the invasive tea spiny whitefly (TSW) A. camelliae has been expanding over East Asia in recent decades. In this study, the genetic diversity of OSW and TSW and of their important parasitoid wasp Encarsia smithi was investigated in China and Japan to enable more efficient biological control policies. We detected two phylogenetic groups (haplogroups A1 and A2) in OSW and three phylogenetic groups (haplotypes B1 and B2, and haplogroup B3) in TSW in China; however, only a single haplotype was detected in each whitefly species in Japan. Based on historical records and molecular data, OSW was considered to be native to China whereas TSW has probably expanded to China from a more southern location in the last 50 years; China appears to be the source region for OSW and TSW invading Japan. In E. smithi, two phylogenetic groups were detected in Japan: haplotype I, associated with OSW, and haplogroup II mostly associated with TSW, except in two locations. These data support the hypothesis that E. smithi parasitizing TSW in Japan did not originate from the existent population parasitizing OSW but was newly imported into Japan following the invasion of its host. [ABSTRACT FROM PUBLISHER]