Most farmers attempting to control slugs and snails turn to baited slug poison, or molluscicide, which usually consists of a bran pellet containing either methiocarb or metaldehyde. Both chemicals are neurotoxins that disrupt that part of the brain charged with making the mouth move in a coordinated fashion—the “central pattern generator”—as the slug feeds. Thus, both neurotoxins, while somewhat effective, interfere with the slugs’ feeding behavior and limit their ingestion of the poison, increasing the probability that some will stop feeding before receiving a lethal dose. Moreover, slugs are not the only consumers of these poisons: methiocarb may be toxic to a variety of species, including varieties of worms, carabid beetles, and fish.
Researchers are experimenting with an alternative compound based on aluminum, which may solve these problems, but this may well have a limited future as we learn more about the hazards of aluminum in the environment. For example, some researchers suggest that acid rain kills trees by mobilizing aluminum in the soil, while others have noted that the human disease Alzheimer’s is more prevalent in areas where levels of aluminum in the soil are high. With farmers losing as much as 20 percent of their crops to slugs and snails even after treatment with currently available molluscicides, there is considerable incentive for researchers to come up with better and environmentally safer solutions.
A promising new direction in molluscicide research involves biological controls. Scientists are exploring the use of nematodes, microscopic worms that are natural parasites of slugs and snails. These nematodes infect and kill the pests without harming other wildlife or plants. A key advantage of this method is its specificity, targeting only the intended pests and offering a more sustainable and eco-friendly approach to pest management. The commercial availability of these biological agents is still developing, but early results show great potential for a future where farmers can protect their crops without relying on harmful chemical toxins.
Question 1
In the passage, the author is primarily concerned with
(A) describing the limitations of molluscicides that affect feeding behavior
(B) proposing alternatives to current methods of controlling slugs and snails
(C) emphasizing the need for an alternative to currently available molluscicides
(D) explaining how molluscicides are used to control slugs and snails
(E) criticizing the use of hazardous material for controlling slugs and snails
Question 2
The author suggests that which of the following is true of the “alternative compound” mentioned in the highlighted text?
(A) It is more effective in destroying snails than in destroying slugs
(B) It begins to affect slugs’ feeding behavior before they ingest a lethal dose
(C) It affects more species of fish than does metaldehyde
(D) It may not be environmentally safer than methiocarb
(E) It may be less damaging to trees than metaldehyde
Question 3
The author cites which of the following as a disadvantage of methiocarb?
(A) It contains high levels of aluminum
(B) It may react with acid rain to kill trees
(C) It has been associated with Alzheimer’s disease
(D) It may be toxic to some species of fish
(E) It may not be as effective in killing slugs as metaldehyde is
Question 4
The passage suggests that methiocarb and metaldehyde would be more effective as slug poisons if it were true that they
(A) disrupt the slug’s digestive processes rather than its reproductive functions
(B) reduce the slug’s ability to taste food
(C) begin to affect the feeding behavior of a slug only after it has ingested a lethal dose
(D) reach the central pattern generator more quickly
(E) accumulate only in the central pattern generator rather than throughout the brain
Question 5
In the context of the passage, what does the word “mobilizing” most nearly mean in the sentence “acid rain kills trees by mobilizing aluminum in the soil”?
(A) combining
(B) neutralizing
(C) activating
(D) releasing
(E) converting
Question 6
The word “incentive” in the last sentence most nearly means
(A) obstacle
(B) motive
(C) substitute
(D) explanation
(E) example
Question 7
What is the tone of the passage with regard to current molluscicides?
(A) strongly condemnatory
(B) cautiously skeptical
(C) sarcastic and dismissive
(D) neutral and detached
(E) optimistic and confident
Question 8
Why did the author mention “farmers losing as much as 20 percent of their crops to slugs and snails”?
(A) To criticize the inefficiency of current pesticides
(B) To highlight the economic urgency driving research for alternatives
(C) To prove that methiocarb is ineffective
(D) To suggest that slugs are immune to poison
(E) To argue that snails are more destructive than slugs
Explanation and Answers
Answer 1: C
The author discusses limitations of current molluscicides and emphasizes the need for better, safer alternatives. This is the central theme. Option A is too narrow, B overstates the author’s role, D is only a factual part, and E exaggerates the tone.
Answer 2: D
The passage warns that aluminum may not be environmentally safer due to links with tree death and possibly Alzheimer’s disease. The other options are not supported or mentioned.
Answer 3: D
The passage directly states that methiocarb may be toxic to species like fish. Options A, B, and C refer to aluminum. Option E is not discussed.
Answer 4: C
Methiocarb and metaldehyde interfere with feeding before a lethal dose is consumed. If they acted only after a lethal dose was ingested, they’d be more effective. The other options are unrelated to this core issue.
Answer 5: D
“Mobilizing” in this context means releasing aluminum from the soil into harmful forms. “Releasing” is the best fit. The other options misinterpret the chemical context.
Answer 6: B
“Incentive” means a motive or reason to act. The sentence shows researchers are motivated to find a better solution. Other choices do not fit the meaning.
Answer 7: B
The author is critical but careful and data-driven. “Cautiously skeptical” best captures the tone. The other options are either too extreme or inaccurate.
Answer 8: B
The 20 percent loss is used to show why more research is needed and to highlight the urgency. It is not used to prove ineffectiveness or compare slugs and snails.
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