Correlation between epicuticular wax content in the leaves of early white cabbage (Brassica oleracea L. var. capitata) and damage caused by Thrips tabaci Lindeman (Thysanoptera: Thripidae)

Trdan, S. and Znidarcic, D. and Zlatic, E. and Jerman, J. (2004) Correlation between epicuticular wax content in the leaves of early white cabbage (Brassica oleracea L. var. capitata) and damage caused by Thrips tabaci Lindeman (Thysanoptera: Thripidae). Acta Phytopathologica et Entomologica Hungarica, 39 (1-3). pp. 173-185. ISSN 0238-1249

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Abstract

In the period of 2001-2002 the susceptibility of five varieties of early white cabbage to onion thrips (Thrips tabaci) attack has been studied. The variety with the longest growth period (72 days) and the firmest head (19.5-21.5 kg/cm2), i.e. Vestri, had the highest mean weight of the head (1220.0 g/head) and the highest net weight of the head (1050.6 g/head), while the mean index of damage (1.18) and the mean yield loss (13.9%) were the lowest in this variety. At higher plant density (16.6 plants/m2) both parameters of the weight of the head were approximately less than half as compared to lower plant density (8.2 plants/m2). Results of the mean net weight of the heads did not show significant differences between different plant densities if the yield was calculated per area unit (m2). The mean content of epicuticular wax differs among varieties, although all varieties show similar relations in its content; the lowest mean content in the third and the fourth exterior leaves of the head, the highest mean content was within the first and the second, and the ninth and the tenth exterior leaves of the head. In spite of the apparent correlation between the content of epicuticular wax and the mean index of damage (with both plant densities its values were the highest between the third and the sixth exterior leaf of the head) caused by feeding of onion thrips hardly perceived negative correlation (Pearson coefficient of correlation between -0.338 and -0.436) were found between these two parameters using statistical analysis.

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