What potential negative impact can volunteer plants have in horticulture?

Volunteer plants can indeed attract unwanted pest species, which is why this option is a valid concern in horticulture. While some volunteer plants may provide benefits, including habitat and resources for beneficial insects, they can also create an environment that is favorable for pests, which can lead to an increase in pest populations. This occurs because the random emergence of these plants may not be in line with the cultivated plants in the area.

Additionally, some volunteer species can serve as hosts or reservoirs for pests and diseases that could spread to cultivated plants, disrupting the balance and health of the horticultural ecosystem. Therefore, managing volunteer plants effectively is crucial to minimize potential pest issues.

The other options do not accurately reflect the potential negative impacts associated with volunteer plants. For instance, introducing beneficial insects is generally seen as a positive outcome, and while volunteer plants can contribute to soil health, they do not always do so. Furthermore, while native plant extinction is a concern in ecological contexts, volunteer plants do not inherently lead to this outcome; their impact on native species varies greatly depending on the specific circumstances and species involved.