Effectiveness of short exposures of propylene oxide alone and in combination with low pressure or carbon dioxide against Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae)
S. Navarroa,*, A. A. Isikberb, S. Finkelmana, M. Rindnera, A. Azrielia and R. Diasa
aDepartment of Stored Products, Agricultural Research Organization, The Volcani Center, P.O. Box 6, Bet-Dagan 50250, Israel
bDepartment of Plant Protection, Faculty of Agriculture, University of Kahramanmaras Sutcu Imam, Kahramanmaras 46060, Turkey
Accepted 25 October 2002
Abstract: Toxicity of the fumigant propylene oxide (PPO) alone and in combination with low pressure (100mm Hg) or 92% CO2 to all life stages of Tribolium castaneum using short exposure times (4 and 8 h) at 30°C was studied. Results indicated that PPO was moderately toxic with Ct products ranging from 120 to 608 mg h/l required to obtain complete mortality of the different life stages. A marked difference in susceptibility between life stages was recorded. Eggs were the most sensitive with a LD99 value of 30.1 mg/l for 4 h, whereas pupae were the most tolerant with a LD99 value of 146.5 mg/l. It was shown that an increase in exposure time from 4 to 8 h resulted in 23%, 42%, 48% and 47% reductions of LD99 values for eggs, larvae, pupae and adults, respectively.
There was no or very limited mortality of all stages except the egg (53% to 62%), when exposed to either 100mm Hg or 92% CO2 for 4 h. However, when 100mm Hg or 92% CO2 were combined with PPO, the LD50 and LD99 values for PPO in all stages except the egg were significantly reduced. Combinations of PPO with 100mm Hg or 92% CO2 produced equal reductions in the LD99 value from 146.5 to about 22 mg/l for the most tolerant pupal stage. Both combinations also produced significant reductions in the LD99 values for larvae and adults (6.3- to 6.6-fold) compared with those exposed to PPO alone. These results indicated that 100mm Hg and 92% CO2 each had a synergistic effect on the toxicity of PPO to T. castaneum. The combination of PPO with vacuum or CO2 can thus provide a potential alternative to methyl bromide.
© 2003 Elsevier Science Ltd. All rights reserved.
Key words: Propylene oxide; Carbon dioxide; Vacuum fumigation; Tribolium castaneum; Synergistic effect
