Biological control or biocontrol is a method of controlling pests such as insects, mites, weeds and plant diseases using other organisms. It relies on predation, parasitism, herbivory, or other natural mechanisms, but typically also involves an active human management role. It can be an important component of integrated pest management (IPM) programs.

There are three basic strategies for biological pest control: classical (importation), where a natural enemy of a pest is introduced in the hope of achieving control; inductive (augmentation), in which a large population of natural enemies are administered for quick pest control; and inoculative (conservation), in which measures are taken to maintain natural enemies through regular reestablishment.

Natural enemies of insect pests, also known as biological control agents, include predators, parasitoids, pathogens, and competitors. Biological control agents of plant diseases are most often referred to as antagonists. Biological control agents of weeds include seed predators, herbivores and plant pathogens.

Biological control can have side-effects on biodiversity through attacks on non-target species by any of the same mechanisms, especially when a species is introduced without thorough understanding of the possible consequences.

Diamagnetic Anisotropy: Diamagnetic anisotropy is the shielding and deshielding depending on the orientation of the molecule with respect to the applied magnetic field.

Anisotropy is the property of a molecule in different orientations which show variations in physical properties along different axes of the molecule.

Downfield shift of protons attached to C=C and aldehydic and aromatic protons can be explained by considering the molecular magnetic fields induced by the action of applied field H0 on pi electrons. The magnetic fields induced by pi electrons are directional, i.e., unsymmetrical. A measurement which varies with the direction in which the measurement is taken is said to be anisotropic. Because the effects of molecular fields induced by pi electrons are direction dependent, these are, therefore, termed diamagnetic anisotropic effects. (These effects are contrasted to inductive effects, which are symmetrical around the proton.) Anisotropic effects occur in addition to the ever present molecular fields induced by sigma bond electrons.

Thus the downfield shift of aromatic protons (benzene absorbs at δ 7.37); alkenic protons (δ 4.6-5.9) and the aldehydic proton (δ 9-10) is not only due to the deshielding effect of sp2 carbon (sp2 carbon has high s character and withdraws electrons, deshielding the hydrogen) but also due to diamagnetic anisotropy of the benzene ring and C=C in alkenes and C=O in aldehydes respectively. These two effects combined together deshield the attached hydrogens in these systems.