At typical application rates, what is the effect of diquat on non-plant aquatic organisms?

• A. It causes significant adverse effects on most aquatic organisms.
• B. It has no effect on any aquatic organism at any rate.
• C. At application rates, no apparent significant effects on most aquatic organisms.
• D. It immediately kills all aquatic life.

Answer: (C)

The main idea here is that diquat, when used at label-recommended application rates, has little impact on non-plant aquatic organisms. Diquat is a contact herbicide that targets plant tissue on contact and does not accumulate in animals. In water, it degrades relatively quickly through sunlight exposure and chemical processes, so the concentration exposure for fish, invertebrates, and other aquatic wildlife stays below levels that would cause significant harm for most species. Because of this, most aquatic organisms show no apparent significant effects at typical use rates.

It's important to follow label directions to avoid higher-than-recommended concentrations, which could pose risks to sensitive species or persistent exposures. The other statements imply either widespread harm, no effect ever, or universal kill, which isn’t consistent with its use and toxicology at standard application rates.