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32
residents indoors in the evenings. This year there was a
negligible nuisance even in the worst areas near Bostall and
Lessness Abbey Woods.
An anti-fly campaign was also instituted. Dust bins,
dust carts, food bins and animal sheds and various premises
were treated with 5 per cent. D.D.T. in Kerosene.
Cockroaches were eradicated principally by Gammexane
dust as some species are resistant to D.D.T.
Bugs were dealt with by D.D.T. spray which never fails
if properly applied.
Three men and an overseer were carefully practised in
the technique of using residual spray, so that inefficiency
from waste, mess or inadequacy were avoided. This time
spent in training has been valuable, as judged from the
absence of recurrence of pests.
Rats and mice take up about 60 per cent. of the men's
time, dealing with sewers under the Ministry of Food Circulars
N.S. 11 and N.S. 12. The methods advocated by the Ministry
of Food were used exclusively and with good results. There
is a considerable infestation of black rat owing to Erith's
riparian position.
A summary of the year's work is given below.
(a) Mosquitoes.
The following sites were treated during the year:—
Allotment Tanks 392
Pools 16
Ditches 7
Wells 15
Bomb Craters 2
432
On initial spraying it was found that mosquito larvae
existed at densities varying from 12 to 900 per square foot.
Routine and systematic spraying reduced except 2 to
negative, and these 2 (i.e. a well and a tank) showed 36 to
120 per square foot respectively and were consequently
treated again.
(b) Flies.
275 Food Salvage bins in the streets were sprayed
monthly with D.D.T. solution from May to September.
The Corporation piggery was likewise treated during
the Summer months.
70 D.D.T. impregnated sheets were made up and
delivered to Nurseries and Borough Maternity Home.