Pest damage can range from leaf damage that has no effect on the value of the fruit to severe damage that kills plants, significantly reduces crop yield or reduces the crop's market value. Pests may also cause contamination of fruit at harvest, reducing its marketability. Fruit pests include insects and mites, pathogens, nematodes, weeds and vertebrates. Effective pest management is based on thorough consideration of ecological and economic factors. The pest, its biology and the type of damage it causes are some of the factors that determine which control strategies and methods, if any, should be used. Pest management decisions largely determine the kind and amount of pesticides used. Pest management decisions represent a compromise between the value of the product, the extent of the pest damage, the relative effectiveness and cost of the control measures, and the impact on the environment. Pesticide application refers to the practical way in which pesticides, (including herbicides, fungicides, insecticides, or nematode control agents) are delivered to their biological targets (e.g. pest organism, crop or other plant). Public concern about the use of pesticides has highlighted the need to make this process as efficient as possible, in order to minimize their release into the environment and human exposure.