However, this method is quite slow, as this organism requires 6-8 weeks to grow, which delays reporting of results.

Not all insects, weeds, and other living organisms require control.

All organisms require certain nutrients in their surroundings (available to them) for survival.

Competitors- other organisms may require the same resources from the environment, and so reduce growth of a population.

It crowds out native species and hogs the nutrients that other organisms require.

Almost all aquatic organisms require oxygen, and in its absence, habitat becomes unusable.

In order to build larger and longer lived bodies, organisms required greater cancer suppression.

Like other anaerobes, these organisms do not require oxygen for growth.

While this suffices on a small scale, more complex organisms require regularization of body temperature.

Higher organisms, being auxotrophic, also require highly specialized growth media.