Diapause is a genetically programmed pause in development or reproduction, triggered in advance by cues rather than by the bad conditions themselves. In the two-spotted spider mite only adult females diapause; the cue is short day length experienced by the immature stages, strengthened by cool temperatures, and diapausing females turn orange-red and stop laying. Reviews of spider mite photoperiodism describe this response in detail.
In practice
Diapause matters indoors in two ways. A 12-hour flowering photoperiod and cool nights can push some mite strains toward diapause, so orange mites hiding in cracks and canopy debris survive between runs. Several beneficials also diapause under short days, notably some strains of Orius bugs and the aphid midge, so they can fail in flower rooms unless a non-diapausing strain is used.
Don't confuse with
- Quiescence: an immediate slowdown when conditions turn bad, reversed as soon as they improve.
- Carmine mite colour: red mites are not necessarily diapausing; some forms are red all year.
Tetranychus urticae, the commonest cannabis mite indoors: a 0.5 mm sap-feeder that stipples leaves pale and spins webbing, breeding fastest in hot, dry rooms.The daily length of light versus dark; photoperiod cannabis flowers when nights grow long enough, rather than at a fixed age.Using living natural enemies, such as predators, parasitoids, nematodes and microbes, to suppress pests and diseases instead of, or before, chemical sprays.Minute pirate bugs of the genus Orius, such as Orius insidiosus, that hunt adult and larval thrips plus mites and aphids; some strains pause breeding under short days.Small soft-bodied sap-sucking insects of the family Aphididae that cluster on stems and leaf undersides, excrete sticky honeydew and multiply rapidly by live birth.The temperatures below which (lower) and above which (upper) a pest's development stops or slows; they bound degree-day models.A unit of accumulated heat above a pest's lower developmental threshold; development finishes when a stage's degree-day total is reached, whatever the calendar says.
