One of the most noxious wind-borne allergens is ragweed (Ambrosia), as evidenced by an estimated 30 million sufferers in the United States alone and a societal cost of over $3 billion. Each plant is able to produce more than a billion grains of pollen over the course of a season, and the plant is the prime cause of most cases of hay fever in North America. Although the plant produces more pollen in wet years, humidity rates above seventy percent tend to depress the spread of pollen by causing the grains to clump.

Ragweed spreads rapidly by colonizing recently disturbed soil, such as that engendered by roads, subdivisions, and cultivation and has adapted to a multitude of climatic conditions, including desert and high mountain areas. Complete elimination is virtually impossible. Physical removal is undone by even one seed or one bit of root left behind. Ragweed regenerates in about two weeks from only a half-inch of stem, usually with additional branching and flowering, so mowing can actually be counterproductive. Ragweed is susceptible to only the most aggressive herbicides, and because ragweed tends to cover large areas, control would mean widespread use of highly toxic chemicals. Control by natural predators? No known mammal browses on ragweed. Some species of Lepidoptera (butterflies, skippers, and moths) larvae feed on ragweed, but this arena of control is not well-funded, and consequently not well-researched. Given the health issues and costs occasioned by ragweed, government funding for natural control research is warranted.

For the following question, consider each of the choices separately and select all that apply.

Which of the following can be inferred about the spread of ragweed pollen?     

A. Ragweed plants adapted to desert and mountain climates tend to spread fewer grains of pollen than do plants in other locations.
B. Some attempts to control ragweed pollen may exacerbate the problem.     
C. The clumping of pollen grains caused by high humidity levels affects the ability of the wind to carry the grains.



The author mentions some species of Lepidoptera in order to     

A. detail a species that may be more effective at controlling ragweed than are the most aggressive herbicides     
B. suggest a potential research avenue to the problem of controlling ragweed that is at present poorly explored     
C. discuss a type of mammal that feeds on ragweed plants and may be successful at controlling the spread of ragweed     
D. plead with the government to spend more money and put more research efforts into finding a natural control for ragweed     
E. argue that complete elimination of the ragweed plant will only be possible if the government funds research into natural controls of ragweed