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How to make an attractive Toxic Sugar Mosquito Bait

Posted Nov 05 2012 12:28pm
How to make an attractive Toxic Sugar Mosquito Bait To lay eggs, females do need blood for its iron and protein. But usually mosquitoes subsist on modest sips of nectar from flowers or from ripe or rotting fruit. And that, according to scientists from Hebrew University in Jerusalem, is an ... Achilles' proboscis - through which the pests can also be poisoned... That's how we came up with fruit juice...Attractive Toxic Sugar Baits." “You can’t move flowering trees around,” said Yosef Schlein, a parasitologist at the university’s medical school. “So you have to use movable bait. That’s how we came up with fruit juice.” Supported by a grant from the Bill and Melinda Gates Foundation, Dr. Schlein and his research partner Günter C. Müller concocted an array of nectar poisons known as Attractive Toxic Sugar Baits that are easy to make, environmentally friendly and inexpensive. In tests in Israel and in West Africa, the baits knocked down mosquito populations by 90 percent. Even better, they nearly eliminated older females, the most dangerous mosquitoes. (Only females bite humans, and only mosquitoes that have already picked up malaria, dengue or another disease from one human can inject it with their saliva into another human.) Dr. Müller and Dr. Schlein tested their idea five years ago at a desert oasis near the Red Sea. Putting out vases of flowering tree branches, they learned that acacias — the thorn trees common in Africa — attracted the most mosquitoes. They sprayed branches with a mixture of sugar water and Spinosad, a bacterial insecticide considered harmless to humans and most beneficial insects. The mosquitoes feeding on them died. Their next test was in a Greek Orthodox monastery in the Judean hills where mosquitoes laid their eggs in underground rainwater storage cisterns. They filled old soda bottles with a solution of brown sugar, the juice of rotting nectarines, Spinosad and a dye. They put each in a sock with a wick that helped keep the sock soaked with the colorful fatal elixir. They suspended a bait at the opening of each cistern. Trapping later showed that up to 97 percent of all mosquitoes in the area were marked with the dye, meaning they had landed on a toxic sock at least once. Within a week, the female population had crashed to near zero; it stayed there for a month. The toxic sugar bait developed by scientists at Hebrew University Medical Center in Jerusalem is made with a combination of fruit juice essences, which are attractive to mosquitoes, and boric acid - a mild, inorganic powder that kills insects when they ingest it. In experiments in a semi-arid region of Mali, in West Africa, the bait - in this case a blend of boric acid with guava and honey-melon fragrances - was applied using a hand sprayer on the vegetation near a cluster of man-made ponds. These ponds are important dry-season water supplies for local villagers and their livestock. They are also breeding grounds for Anopheles gambiae, the mosquito that carries the most deadly form of malaria. For comparison, investigators sprayed grasses and leaves near other ponds with a solution of sweet fragrances only. Both baits contained a dye that marked any mosquito making contact, so scientists could count how many had actually fed on the lure. Josef Schlein, a medical entomologist who led the study, says the results after 38 days showed the bait containing both sweet fragrances and boric acid proved to be very effective at killing mosquitoes."In Mali, we got down by some 80 percent, the females, and 90 percent of the males," he said. "But the area is full of little ponds in there, so it is impossible to stop mosquitoes from flying from an untreated pond to a treated pond." At the control sites that were treated with fragrances only, Schlein says upwards of 75 percent of mosquitoes fed on the fake bait. Their most recent study, published in Malaria Journal, was done in West Africa, where malaria is a major killer, especially of young children. The scientists chose a rural road in Mali running past ponds where two aggressive mosquito species breed — Anopheles gambiae and Anopheles arabiensis. They sprayed weeds there with a solution of the fermented juice of local guavas and melons mixed with dye and boric acid. Within a few days, they saw 90 percent die off. Boric acid is much less expensive than Spinosad. It is also about as harmless to humans as table salt is. It is a chief ingredient in Silly Putty. Dr. Schlein said he had heard that some Malians sampled the alcoholic bait brew, with no ill effects. But it kills insects that eat it. It is common in cockroach control; when a thin layer is spread on floors, cockroaches take it in when they preen their feet. “You can buy it by the truckload,” Dr. Christensen said. “And it kills in so many ways that there’s never been resistance to it. Some authorities think there never will be.” http://www.malariajournal.com/content/9/1/210 Schlein explains most people don’t realize that female mosquitoes typically feed on sweet plant nectars to survive. Their more familiar blood meals, when mosquitoes bite people, are part of the reproductive cycle. The researchers’ goal now is to make a lure that’s even more irresistible to mosquitoes. Research leader Josef Schlein notes that boric acid poses little risk to humans and other mammals, so it’s possible a mosquito lure could be developed for use indoors. Given the non-toxic simplicity of this new bait, the Hebrew University entomologist says it’s a marvel that other scientists didn't think of it sooner.
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