With Donald Roberts about to give testimony before Congress it is instructive to look at his Senate testimony on October 6, 2004.
Just as the use of DDT in house spraying brought spectacular reductions in malaria,
declining use of house spraying brought spectacular increases in malaria. … Data from Asian countries show similar
relationships. Figures 2-5 contrast malaria rates in recent years with the years when DDT was
used. The data represent annual parasite indexes (a population-based index of malaria
prevalence) during the period from 1995-99 compared with identical data from 1965-69.
Differences in rates for the two performance periods are stunning.
Indeed they are. Here is his most stunning figure, for Sri Lanka showing an increase from 0 API to almost 20.

But if you check the source he cited, WHO reports for South-East Asia, you’ll find that in reality the malaria rate actually decreased from 16 to 11.

And if you wanted to see the effect of stopping DDT use, surely it would make more sense to compare the five years before DDT spraying stopped in 1976 (malaria rate 22) with the five years after (a much lower malaria rate of 3.4).
The number cases of malaria in Sri Lanka came from the graph in this WHO report. The population figures for computing rates came from The World Bank. Data and calculations are in this spreadsheet.
