A senior Tel Aviv University plant biologist has warned that a new, highly allergenic species of ragweed that has migrated to Israel recently from Europe is spreading rapidly, posing a major public health threat. Dr. Yoav Waisel called on the ministries of Health, Environmental Protection and Agriculture, as well as the Nature and National Parks Authority, to work together to spray the weeds in order to prevent the species from spreading from the Sharon Plain and the Hula Valley in the Upper Galilee to the rest of the country. Their warning about the ironically named Ambrosia (food or drink of the Greek gods) appears in the latest (December) issue of IMAJ, the Israel Medical Association Journal. Waisel told The Jerusalem Post that ragweed first appeared in North America hundreds of years ago and now comprises 42 species. Ambrosia maritima, which has been multiplying in southern Europe and Israel's coastal plain for many decades and has been extracted in his TAU lab, spreads very slowly. But newer species, including Ambrosia artemisifolia, Ambrosia trifida, Ambrosia grayi and Ambrosia tenuifolia followed. The newest threat to one million allergy-prone Israelis (15 percent of the population) is Ambrosia confertifolia, which has invaded the Hula Valley and Emek Hefer/Nahal Alexander area and flowers in late August. The species is said to feel so "at home" here that it is rapidly spreading along the sides of roads and railways, field margins, open areas cleared by tractors, and stream banks. "There is a law in France requiring the destruction of this aggressive allergenic invader with spraying, and other European countries are becoming increasingly aware of its threat to health," explained Waisel, who has been monitoring the spread and taking pollen counts of each species in the field. "Attempts to eradicate the invading species were made only on a very small scale and discontinued due to damage to agricultural crops that was caused by improper handling of the herbicides," said Waisel. He warned that regional and government authorities were not taking any action aimed at eradicating or even limiting the spread of this invasive species. "This is a clear case where the impotency of the authorities will result in serious public health problems that will cause great suffering to thousands of people and high costs to the public health system," Waisel said. The TAU plant biologist added that once a new species takes over too large an area, it becomes "out of control." Prof. Yosef Mekori, dean of TAU's Sackler Medical Faculty and himself an allergy specialist, told the Post that there was "no doubt allergies increase from the exposure to new allergens... among people with a genetic propensity. On the basis of pollen counts, we build diagnostic tools such as skin testing, but we don't really know about different species of ragweed." He added that for years, doctors did not know that pecan trees were highly allergenic, as are olive trees, but more people who lived near them developed allergies and asthma. However, Prof. Meir Shalit, head of the clinical immunology and allergy unit at Hadassah-University Medical Center in Jerusalem's Ein Kerem, had a view very different from Waisel's. "While I accept the facts that there is a new species of Ambrosia, I say there are plenty of new ones, and the arrival of A. confertifolia will cause only a minor rise of allergy in sensitive people," Shalit said. "It is wishful thinking to destroy all the weeds and cut down trees, and allergy sufferers should not panic. But the authorities must work to minimize air pollution, as diesel particles increase the effects of allergen particles and boost their penetration into the respiratory mucous membranes." After receiving the IMAJ article, the Health Ministry declined to comment except to say that it was not responsible for eradicating allergenic plants. The Environmental Protection Ministry did not comment either. But the Agriculture Ministry's chief herbologist, Dr. Tuvya Ya'acoby, said he had attended international conferences on the new Ambrosia species and the damage they could cause humans. The reactions, sometimes serious, can affect 20% to 30% of people exposed to them during flowering and the spread of pollen in the air, he said. Ya'acoby added that all A. trifida and A. artemisifolia had been destroyed by herbicide. But he conceded that it was much more difficult to rout the A. confertifolia. In Europe, unlike Israel, herbicide spraying is allowed only in agricultural land and not in open spaces, he said. "It is not clear whether problematic species can be sprayed in high concentrations in all the areas, he said, "but we in the plant protection services are working to find a solution."