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IAA (indole-3-acetic acid) A naturally occurring auxin produced in apical meristems of both roots and shoots. (Nelson, 2003)

IBA (indole-3-butyric acid) A synthetically produced auxin. (Nelson, 2003)

Infiltration heat loss Loss of heated air from the greenhouse through cracks. (Nelson, 2003)

Inoculum The pathogen or its parts that can cause disease; that portion of the individual pathogens that are brought into contact with the host. (Nelson, 2003)

Insecticide An agent or preparation used for killing insects. (Nelson, 2003)

Internode The portion of the plant stem between two nodes. The node is the portion of the stem where one or more leaves are attached. (Nelson, 2003)

Interveinal Pertaining to the space between the vascular tissue (veins) on a leaf. (Nelson, 2003)

IPM (integrated pest management) A holistic approach for managing pests including insects and related animals, pathogenic diseases, and weeds. Components of the program can contain restriction of pest entry into the cultural area, establishment of environment conditions unfavorable to the pest an hand, biological control, and only when necessary, the use of chemical pesticides. (Nelson, 2003)