If one has water features, birdbath or open reservoirs one inevitably will have mosquito larvae. These if unchecked will grow to nice sizes and develop into the nuisance they are.
OK, so only the female will be after your blood – homing in via a combination of infrared and dioxide – they have the uncanny habit of doing this just when one is about to go into deep noddy land.
Fish do help, if not fed too well they will go after these wriggly larvae. So will nutes and other inhabitants of the water. Flowing water that lets the surface ripple is also good as the larvae need to come up for air and need quite water to emerge into mosquitoes.
If the water is not for display one can just put one or two drops of oil on the surface, this will spread, form a film and prevent the larvae from breathing.
There are gazillions of reasons why any of the above is not practical or simply not desirable – so what to do?
I hate the idea of having my private beach taken over by mossies!
There isÂ Bacillus Thuringiensis, a naturally occurring soil dwelling bacterium. This has been isolated into main strains each of which is only toxic to specific insects.
Aizawia – Moths
Kurstaki – Moths
Israelensis – Mosquitoes & Flies
Tenebrionis – Beetles
Israelensis is soluble in water – lives in water and attacks the mosquito larvae.
In America it is widely and successfully used and exists as powder to mix in water as well as so called “dunks”. These act like slow release fertilizer and are good for 30 days.Â Just drop and forget. It is rated at being completely safe for all other animals and obviously humans.
Here in Spain I have so far found one licensed source that can supply B.t. israelensis as a gram positive powder in 50g or 1KG lots.
So I got hold of it and trialed it over the last 10 days, by adding approx. 1g every day to our water feature that holds approx. 250l of water and zillions of larvae.
Not much happened for the first days, than the larvae became noticeably fewer and I found dead ones floating.
As of today there is hardly any wriggly about. The good news isÂ that the boatmen, the skaters, snails, water fleas all seem totally unaffected and go about their business as usual.
As the breeding circle or larvae stage for mosquitoes is around 4 days or so I recon after the initial stage I can now drop the dosage to about 1g every 4 days or simply sprinkle a tiny amount into the feature each day. Thus one or two 50g tubs will last me for the season.
If you are interested in more details or the latest source drop me a mail.
I’m in the process to find a good cheap resource and also trying to find licensed dunks here in Spain.
It is also quite feasible to spray wetlands or areas of ground that are water logged and have the same effect. Personally I think this is great as using any pesticides is guaranteed to do more harm.
Mosquitoes – not in my butt!
Update 2009: In March we have started to use Thuringiensis again. Boatmen and dragonfly larvae have survived the winter. We have lots of little boatmen (cute) but no mosquito larvae.