Which term relates to the unwanted competition from weeds for resources?

The term that best relates to the unwanted competition from weeds for resources is "competitive exclusion." This concept describes the principle that when two species compete for the same limited resources, one will typically outcompete the other, leading to the local extinction of the less competitive species. In the context of weeds, they can outcompete desirable plants for sunlight, water, and nutrients, which is detrimental in agricultural or landscaped settings.

While "plant competition" may seem closely related, it refers generally to how plants compete with each other and does not specifically emphasize the outcome of that competition. "Resource allocation" pertains to how resources are distributed among organisms, but does not address the competitive aspect. Finally, "food web" is a broader ecological concept that illustrates the feeding relationships between organisms, which does not directly relate to the competition for resources among plants.