USE OF MENAZON SEED DRESSING TO DECREASE SPREAD OF VIRUS YELLOWS IN SUGAR-BEET ROOT CROPS

Menazon, an organophosphorus insecticide (only slightly toxic to mammals), applied to sugar‐beet seed, decreased the proportion of seedlings infested with aphids during May and early June and the number of aphids per plant during June and early July to one‐third of that in the control plots. It also checked the spread of virus yellows. Of eight field trials in 1965, 1966 and 1967 in which more than 10% of the plants in plots not treated with insecticide had yellows, menazon seed dressing increased sugar yield by about 8 cwt per acre. Spraying with demeton‐methyl when ‘a spray warning’ was issued in the area gave a similar increase, and had no further effect on plots sown with menazon‐treated seed. Menazon‐dressed sugar‐beet seed is recommended in regions where yellows is usually prevalent, or where there is reason to expect a large aphid infestation. Copyright © 1968, Wiley Blackwell. All rights reserved