Pests in the plant world refer to detrimental species that fixate on to plants, making them unfit for harvest. Although most of these organisms tend to be insects, some fungi or plants may be classified as pests as well.Any field is vulnerable to plagues. Some organisms are harmless but most are harmful to the roots, leaves and overall health of a plant. That is why it is important to prune plants carefully and take the necessary precautions for proper control of the blight.