Field experiments on the control of aphis-transmitted virus diseases of Hyosujamus Niger

1 Aphis infestation of the first‐year's growth of Hyoscyamus niger grown as a biennial crop, was reduced by spraying with a solution of nicotine and soft soap for the first 8 or 9 weeks.

2 The greatest effect was obtained by spraying at weekly intervals, but spraying fortnightly and spraying weekly in June or weekly in July, also slightly reduced the infestation.

3 The percentage of infection by aphis‐transmitted viruses was lower on the sprayed plots than on the unsprayed.

4 No effect of treatments on yield was obtained at the first cropping in the first year of growth which coincided with the end of the spraying period.

5 As a result of weekly spraying in the first year a 30 per cent increase of yield was obtained in the third crop taken in May of the second year.