Gamma irradiation for after harvest disinfestation of diapausing twospotted spider mite (Acari: Tetranychidae)
1995
Lester, P.J. | Petry, R.J.
Adult diapausing twospotted spider mite, Tetranychus urticae Koch, were treated with 150-5,000 grays (Gy) gamma irradiation. Mites were placed on bean leaves, and oviposition, egg hatch, and mite mortality were recorded every 2 d. Analysis indicated that 351 Gy would give Probit 9 (99.9968% mortality) quarantine security for the production of only sterile eggs. This treatment appears to be of most use as a quarantine method. The dose to inhibit 99% of oviposition (LD99) was estimated to be 2,106 Gy; the LD99 required to kill mites within 10 d of treatment was estimated to be 6,582 Gy. These doses are likely to produce unacceptable damage to most horticultural produce. Doses between 150 and 600 Gy significantly increased estimated time until 99% mortality after treatment (LT99) of mites, relative to control mortalities. Mites irradiated at 350 Gy after being in diapause for 1-12 wk produced no viable eggs, but mites that had been in diapause for longer periods produced nonviable eggs at a significantly faster rate. Diapausing T. urticae appear more tolerant to irradiation than nondiapausing mites.
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