Effect of osmotic desiccation on longevity and temperature tolerance of Phasmarhabditis hermaphrodita (Nematoda: Rhabditidae).
Limited storage stability severely restricts the biological control potential of slug-parasitic nematodes. In a series of experiments, we evaluated the effects of temperature and osmotic desiccation on the short- and long-term survival of the slug-parasitic nematode Phasmarhabditis hermaphrodita. Nematode survival in petri dishes at 1,500 infective juveniles/ml did not differ significantly at 5, 10, and 15 C but declined rapidly at 25 and 30 C. At 25 C about 50% of the nematodes survived for 4 wk, but at 30 C no nematode survived past 1 day. About 50% of the nematodes survived for 32 wk at 20 C. About 35-40% of the nematodes survived up to a year at 5, 10, and 15 C. Phasmarhabditis hermaphrodita showed poor survival under osmotic desiccation in glycerol with 15 and 20% glycerol significantly reducing survival at 5 and 15 C. Although the nematodes tolerated 10% glycerol, this level of desiccation also did not enhance long-term survival at either 5 or 15 C. There was a significant decrease in nematode survival in 10% glycerol at 25 C during the first 2-3 wk, but about 16% of the nematodes survived for 6 wk in 10% glycerol as compared with only 1% survival in water. The greatest benefit of osmotic desiccation in glycerol was observed in the enhanced survival of P. hermaphrodita at temperature extremes. Over 96% of the nematodes survived a 6-hr exposure to 35 C in 10% glycerol, whereas only 9% survived in water. Similarly, over 90% of the nematodes survived an exposure to -20 C for 4 hr in 10% glycerol, but less then 2% survived in water. We conclude that 5-15 C is an optimum temperature range for the storage of P. hermaphrodita. We also conclude that osmotic desiccation in 10% glycerol can substantially increase survival of P. hermaphrodita at temperature extremes (35 and -20 C) for short periods but has no effect on nematode longevity at the optimum temperature range of 5-15 C.
Grewal
Sukhbir K
SK
Department of Entomology, Ohio Agriculture Research and Development Center, Ohio State University, Wooster, Ohio 44691, USA. grewal.9@osu.edu
Grewal
Parwinder S
PS
D000818:Animals; D003890:Desiccation; D008136:Longevity; D009995:Osmosis; D017172:Rhabditoidea / Q000502:physiology*; D013696:Temperature; D013997:Time Factors; D014867:Water / Q000737:chemistry
D014867:Water