DAMPING OFF. Decay of seeds in the soil or the young seedlings before or after emergence. Most evident in young seedlings that wilt and topple over due to rot at the stem base.

DANGER. Signal word for a highly toxic pesticide. The LD for these pesticides is 0-50 mg/kg body weight.

DENITRIFICATION. The reduction of nitrates or nitrites to elemental nitrogen.

NO3 => NO2 => NO => N2ON2 escape as gases.

DESICCATION. Injury to turfgrass due to lack of moisture in the soil or air.

DETHATCHING. The removal of thatch. Performed when a heavy layer of thatch has accumulated, usually done with a vertical mower.

DEW. Moisture that condenses from the air onto leaf surfaces cooled by radiation of heat into the night sky. Also see guttation.

DICHONDRA. (Dichondra spp). A dicotyledenous plant used as a lawn substitute. It has kidney shaped leaves and tends to creep.

DICOTYLEDON. A group of plants characterised by having two seed halves or cotyledons and net venation.

DIFFUSION. The movement of a substance from a region of higher concentration to a region of lower concentration by random molecular movement.

DORMANT. Temporarily inactive, but still alive. Grasses become dormant to withstand severe environmental conditions.

DRIFT. The movement of small particles or vapour from the spray area to the surrounding environment.