الفهرس 
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Abstract
Two controlled-release chemical formulations (a copolymer
film and a polyester tablet) of organic tin compounds were
biologically assayed for their efficacy as mosquito larvicides.
Laboratory-bred third instar larvae of Culex RiRiens L.”were used
in these studies. The results obtained are summarized as foilowsl
1. A controlled-release TBTI-MMA copolymer formulation was successfully
prepared in the laboratory as films painted on PVC
plates.
2. When accumulated toxicity was tested on the larvae a significant
gradual increase in larval mortality was noticed till it
reached 10(17. in the 10th week. When the plate was removed, the
mor~ality was constant to the 14th week then a significant
gradual decrease was observed till the 24th week when normal
mortality was observed as in the untreated larvae.
3. When weekly toxicity was tested continuous fluctuations in
larval mortality was noticed till the 24th week then a gradual
decrease up to the 28th week occured when normal mortaliby was
established.
4. The released toxic compounds from the copolymer formulation
degradated into the non-toxic daughter compounds after about
B weeks.
5. Both the acid and alkaline medium increased the rate of
release of the toxic compounds from the copolymer formulation.
However, the alkaline medium seemed to be significantly more
effective in enhancing the release than the acidic medium.
6. Generally low temperature (lOdC) decreased or almost stopped
the release of the toxic compound from the copolymer formul~
tion, however, at higher temperature (25dC) the release
was significantly increased.
7. The copolymer formulation continued releasing its tOM!C
compounds up to more than 24 weeks in the natural outdoor
cond’iti ons.
8. When the accumulated
copolymer formulation
increase was observed
which this amount was
amounts of tin released from the
were chemically
throughout the
almost constant
assayed, a gradual
first 9 weeks, after
till the 21st week.
However, when the water was changed weekly, the amount of tin
showed irregular release from the copolymer formulation,
giving a series of fluctuations throughout 21 weeks.
9. A cured polyester formulation was successfully prepared in the
laboratory as tablets •
10. When accumulated toxicity released from the polyester
formulation was bioassayed, a gradual increase in larval
mortality was observed till the 3rd week and continued almost
constant to the 9th week although the tablet was removed
after the 7th week. Larval mortality then sharply decreased
and equalled to that of the control after the 13th week.
11. When water was changed weekly, the released toxicity of
polyester formulation showed a series of fluctuations in the
first four weeks, then sharp decrease in the larval mortality
was observed till the 7th week when the larval mortality
equalled the larval mortality of the untreated control.
12. The released toxic compounds from the polyester formulation
degradated into non-toxic daughter compounds after about
6 weeks.
13. When the accumulated amount of tin released from the polyester
formulation was chemically assayed, this amount
increased gradually throughout the first 7 weeks, after
which it was almost constant till the 9th week. However,
when water was changed weekly, the amount of releas,d tin
showed a gradual increase in the first four weeks, after
which irregula •...e•l.e.a.se was observed till the 9th week.
The histopathological examination indicated that the TBTI-MMA
copolymer formulation caused serious changes to the
epithelial gut cells, muscles, fat bodies and Malpighian
tubules.