Incidence of yellows in sugar beet as affected by variation in plant density and arrangement

Abstract

AbstractAphid species found infesting sugar-beet in Tasmania were Aphis craccivora Koch, Aulacorthum solani (Kalt), Macrosiphum euphorbiae (Thos.) and Myzus persicae (Sulz.). The activity of infective alatae over plots of sugar-beet established by sowing at different densities and arrangements to produce 12 treatments was gauged by recording the numbers of plants which became affected with virus yellows symptoms. The incidence of yellows increased as plant density decreased and as plant arrangement altered from rectangular to more square patterns. A regression equation of the form: where a, b, c and d were constants and x and y the intra- and interrow spacings, respectively, accounted for 92% of the variation produced by the 12 treatments. These results indicate that the incidence of virus infection in row crops resulting from aphid flight activity may be manipulated through altering plant density and arrangement.