GMATNinja

I have a slightly different perspective on option E! Yes! Option E that none have struggled eliminating!

(E) The species of insect that has infested cotton plants has never been known to attack soybean plants.

All these people grew soybeans all these years. So they do not really know if their land has insects that are known to attack cotton.
So according to option E, the insects that attack cotton and soy are not the same.
So maybe the insects might attack the cotton because it is something common there?

I guess I am sliding into the "if/maybe" dimension again?

The plan is to stop producing cotton, and start producing soybeans.
Therefore, anything that makes cotton less attractive will only strengthen the plan. This is what C does, by telling us the price for cotton hasn't gone up.
So C strengthens, not weakens, the plan.
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Let's stay focused on the conclusion we're given, then ask whether choice (E) weakens that specific conclusion.

We know that the plan is for soybean farmers to cease growing soybeans and begin raising cotton instead. This plan will "increase [the farmers'] income significantly" by taking advantage of the high price of cotton. The correct answer choice is the one that most seriously weakens the plan's chance of success.

Answer choice (E) states:

This tells us that soybean plants have never been attacked by the insects that infested the cotton plants. Therefore, it's unlikely that this insect infestation will affect soybean plants in the same way it has affected cotton plants.

So what? This information does not weaken the plan's chance of success, because it does not change the evidence that the farmers used to justify their plan in the first place (the dramatically high price of cotton and the stable price of soybeans). If anything, this choice reinforces why we expect the price of soybeans to remain stable.

As for your analysis: yes, you're sliding into "if/maybe" here. Let's clarify.

The passage states that the insect infestation occurred in "certain cotton-growing regions of the world." Answer choice (E) does not provide any evidence that Ortovia is in one of those regions. Also, the fact that soybean plants are not attacked by the same species that infested cotton plants does not provide any evidence that this species does live in Ortovia. Therefore, we cannot infer that the insects are present based on the information in the answer choice.

On the other hand, the information provided by answer choice (B) directly undermines the plan by providing a reason to doubt that the cotton infestation will continue -- consequently lowering expectations that the dramatic increases in the price of cotton will last. So (B) is a much better option than (E).

I hope that helps!
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(B) Tests of a newly developed, inexpensive pesticide have shown it to be both environmentally safe and effective against the insects that have infested cotton crops.

Weaken's most seriously weakens the plan’s chances for success

IMO B

Plan: cease growing Soy, grow cotton to take advantage of high price of cotton to increase income significantly
p1: inset infestations caused dramatic increases in price of cotton on world market
p1:price soybeans remain stable

Weaken chance for success:
A - Incorrect - Increase in Soy doesn't weaken chance for success of Cotton
B - (potentially - could alleviate problem causing prices to be so high)
C - Incorrect- no sharp increase doesn't impact current high price of Cotton
D - Incorrect - they are currently paying 'high' prices, and the plan doesn't say anything about charging "higher" amounts
E - Incorrect - Doesn't impact the plan to grow cotton, it just solidifies the case that Soy is stable