Abstract
The effects of intercropping of Brassicaceae with coriander (Coriandrum sativum), dill (Anethum graveolens), African marigold (Tagetes erecta) and calendula (Calendula officinalis) on the abundance, species richness and diversity of predators and parasitoids of Lipaphis erysimi have been assessed. The numbers of aphids, parasitized aphids and natural enemies were determined during two consecutive phases. The first period comprised the vegetative phase of companion plants up to the onset of flowering and the development of kale up to the start of harvesting, while the second period encompassed the late flowering of companion plants up to senescence and the complete harvesting phase of kale. The establishment of L. erysimi and its natural enemies during the first period was enhanced by the climatic conditions and the additional nutritional resources offered by companion plants. Over the complete 13 week period, the abundance of natural enemies in kale intercropped with African marigold, calendula, coriander and dill increased by factors of 3.1, 2.1, 2.0 and 1.6, respectively, compared with the kale monoculture, while species richness increased by 1.8-fold in kale/African marigold intercrop and by a factor of 2.7 in the other treatments. The predominant predators were Syrphidae larvae and Hippodamia convergens whereas the predominant parasitoid was Diaeretiella rapae. The diversity of natural enemies was similar in all crops owing to the high proportion of syrphids in relation to the other groups of insects. The improved resources offered by companion plants can be exploited in the conservative biological control of insect pests. Key words: Conservation biological control, natural enemies, insect seasonality, Hemiptera, Aphididae, Asteraceae, Apiaceae, Lipaphis erysimi, abundance, richness, Syrphidae, ladybird, kale
Highlights
Increasing plant diversity within an agriculture-dominated landscape can bestow a setting approximating to that of the natural environment
Over the complete 13 week period, the abundance of natural enemies in kale intercropped with African marigold, calendula, coriander and dill increased by factors of 3.1, 2.1, 2.0 and 1.6, respectively, compared with the kale monoculture, while species richness increased by 1.8-fold in kale/African marigold intercrop and by a factor of 2.7 in the other treatments
The results presented revealed that establishment of L. erysimi and its natural enemies in kale crops were influenced by the climatic conditions and nutritional resources of the host plant
Summary
Increasing plant diversity within an agriculture-dominated landscape can bestow a setting approximating to that of the natural environment. For natural enemies of crop pests (Alignier et al, 2014). While the selection of appropriate companion plants for successful management of agricultural landscapes is important, relatively few studies have focused on the influence of habitat on the relationship between insect pests and their natural enemies (ChaplinKramer and Kremen, 2012). C.) is one of the most popular vegetables in Brazil, and is of considerable economic importance, especially to smallscale farmers, so we use this plant as a model, Lipaphis erysimi (Kaltenbach, 1843) (Hemiptera: Aphididae) being one of the most important pests of brassicas on the world. Kale and other species of brassicas crops throughout the world are constantly plagued by L. erysimi, a specialist brassica aphid that attacks the terminal portions of stems and inflorescences, causing curling and yellowing of the plant, and acts as a vector for phytopathogenic viruses (Blande et al, 2008)
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