After setbacks, good results!

Once we got our proposal funded, we jumped into the business of assessing the efficacy of entomopathogenic roundworms (ER) to kill larvae of the mosquito A. aegypti.  It was a disaster... the larval mortality in our controls checks was high, what precluded any conclusion.  Our controls were dying probably because of excessive chlorine in the city water; some bacterial infection in the mosquito larval cultures; or perhaps toxic chemicals being released from brand new plastic pots we used.  After several adjustments, we started to obtain useful data in the assays conducted in household floor drains, where mosquito females often lay their eggs.  We used four sizes of floor drains (types 1 through 4, clockwise from top left).

 

Figure A

In Figure A (below) we see that in the smallest floor drain (type 1), mortality reached nearly 80%, but this good result must be saw against a (still) high mortality in the control checks. The efficacy of ERs to kill larvae declined in types 2 to 4 because their larger bottom area (in cm2) reduced the chances of larvae ingesting the ERs and getting infected.

We improved the experimental conditions and increased the amount of ERs applied to the drains.  Bingo! The efficacy of ERs was considerably higher, with minimal death in our control checks (Figure B).

 

Figure B