Thursday, September 4, 2014

Mosquito fogging in private properties

I can never understand the rationale of frequent mosquito fogging at private properties. Don't they know that it is useless considering that the toxic fog was only effective within their compound and that the mosquitoes will come back to repopulate their estate after a period of time has lapsed (unless the chemical used are those environmentally unfriendly type that cannot deteriorate/degrade and hence might pose a health long term hazard to people)?

I'm not saying that we shouldn't be fogging mosquitoes. I'm just saying that fogging frequency should be moderate so that we don't overdo it. Constant fogging will only increase the resistance of mosquitoes towards the chemicals used (similar to the effect of overusing antibiotics that caused bacterial resistance to antibiotics). Furthermore, we might also be killing slower flying/moving insects, an unintended casualties.

I think the best way to prevent "mosquito bloom" would be to remove their breeding grounds. It's really hard to do than thought. Mosquitoes can breed at places we can't even reach. They are resourceful and adaptable. These mosquitoes could also breed on unreachable tree (or plants) crevices with trapped water, and they could thrive especially during rainy days.

The claim that certain plants are natural mosquito repellants are not scientifically proven BUT have been used in earliest times, from which modern repellants were developed from (e.g. citronella). These plants could act as decoy to overwhelm mosquito senses.

Another useful plant to have around would be the pitcher plant (Nepenthes spp.). Although these plants have been shown to harbour mosquito larvae, a symbiotic relation of these plants with pitcher ant (Camponotus schmitzi) ensures that these mosquito larvae are eliminated early. Hence, it is crucial to have both of pitcher plant and ants in order to effectively control mosquitoes. Otherwise, pitcher plant could be a mosquito breeding place (although at very low frequency as compared to other types of breeding grounds)...

The use of electronic mosquito repellents are doubtful. The claim of efficacy of these devices are based on the believe that the frequencies produced mimicked predatory noise or annoying to mosquitoes. However, recent studies have debunked such claims. There was no effect of electronic repellents in repelling mosquitoes in one study, whereas in another independent study, such electronic devices could be increasing mosquito bites (akin to ringing the dinner bell). Also, the electronic zappers that are supposed to be zapping and killing mosquitoes have been found to be doing more harm to harmless insects than mosquitoes. For example, outdoor bug zappers actually killed 0.22% insects corresponding to biting insects whereas the rest was harmless and beneficial insects.

All in all, constant fogging is useless considering that mosquitoes will become resistant to the chemicals if overused. Controlling mosquito breeding grounds is more useful but it will be challenging to beat the resourceful and adaptable mosquitoes. Planting natural mosquito repellents could help alleviating bites by acting as decoys and messing up mosquito senses (however, some studies have found that the phytochemical level is too low to produce sufficient effect, e.g. citronella concentration too low in these plants to be effective). However, considering that these plants have been used in ancient times should provide credit that there could be benefit in them. Last, the use of electronic mosquito repellents are useless and could be detrimental. Similarly, outdoor zappers only zap beneficial insects while the percent kill for mosquitoes are extremely low.

P.S. Other claims such as increasing bat population will help minimize mosquito population is misleading. Although bats do consume mosquitoes as part of their diet, but they only eat mosquitoes when other food sources are unavailable. Similarly, although we do take bitter gourd, but we don't eat them regularly or make them as our main diet. Hence, bats won't be the natural predator that will help eliminate mosquito menace.

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