EFFECTS OF SUCROSE SPRAYS AND DARKNESS ON APHID COLONIZATION OF SUGAR BEET AND ON APHID TRANSMISSION OF YELLOWING VIRUSES

In the glasshouse, adult, apterous Myzus persicae (Sulz.) and Aphis fabae Scop, settled better and deposited more larvae on sucrose‐sprayed sugar‐beet plants than on water‐sprayed plants. M. persicae settled badly and deposited few larvae on plants that were kept in the dark before or after infestation. The effects of darkness on aphids were reduced by spraying the host plants with 10% solutions of sucrose before infestation. Viruliferous M. persicae transmitted beet yellows virus (BYV) and beet mild yellowing virus (BMYV) less efficiently to dark‐treated plants than to those grown in normal daylight. Spraying sugar beet with sucrose before inoculation with viruliferous M. persicae increased the proportion of successful BYV transmissions but only when the plants were dark‐treated. The effects of sucrose and darkness on settling and larviposition of aphids and on virus transmission may be related to changes in the concentration of carbohydrates, particularly sugars, in the leaves. Copyright © 1969, Wiley Blackwell. All rights reserved