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Field studies on the influence of surrounding collards with non host plants revealed that the flea beetle, Phyllotreta cruciferae (Geoze), occurred significantly (P < 0.05) more on nonbordered control collards (x¯ = 121.2) than on collards bordered by catnip (x¯ = 77.0), southern wood (x¯ = 58.7), tansy (x¯ = 49.5), and wormwood (x¯ = 40.5). However, P. Cruciferae counts on collards bordered by hyssop (x¯ = 100.4) and santolina (x¯ = 83.1) were not significantly (P > 0.05) different from the control. Foliage damage in all treatments, including the nonhost companion plantings, was extensive and reduced the marketability of the vegetable. Thus, although companion planting significantly reduced P. Cruciferae populations in some situations, it did not protect the plants from economic damage.
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Latheef et al. (1984) studied this question.
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