INFLUENCE OF PHYSICAL PARAMETERS ON THE C ONTROL OF THE TOBACCO BEETLE LASIODERMA SERRICORNE FAB (COLEOPTERA, ANOBIIDAE) WITH CARBON-DIOXIDE UNDER HIGH-PRESSURE

The tobacco beetle leeds to severe losses in stored tobacco and tobacc o products, drugs, spices and other foodstuffs. Eggs of Lasioderma ser ricorne died after treatment in a thermostatisized pressure chamber of 100 ml at 20 degrees C with 25 bar, 30 bar, 35 bar and 40 bar CO2, re spectively, after 80, 52, 37 and 20 min, respectively. Reduction of th e temperature to 15 degrees C required expansion of the lethal treatme nt time of about 25%. Control of larvae was obtained at equal conditio ns after 30, 15, 7 and 3 min, respectively, with similar tendency afte r reduction of the temperature. Increase of the temperature to 35 degr ees C reduced that lethal exposure time for also about 25%. At 20 bar 120 min were necessary at 15 degrees C, 95 min at 25 degrees C and 20 min at 35 degrees C, for complete control (LD95). With adult beetles i n addition to the mentioned parameters 15 bar CO2 at 25 degrees C requ ired 48 min, 20 bar 25 min, 30 bar 3 min, 35 bar 2 min and 40 bar 1 mi n for complete control. Cooling at 15 degrees C led to expansion of th e lethal time at 15 bar to 150 min, at 20 bar to 40 min, at 25 bar to 30 min and at 30 bar to 10 min, respectively. Heating to 35 degrees C helped to reduce these times by about 50% at the given conditions. Eff icacy of this method seems to be strongly temperature dependent. The a bsolute effects are greater at pressure of 20 bar than at 30 bar. With 5 min treatment of adult tobacco beetles at 25 degrees C and 20 bar C O2 and time to build up the pressure and pressure decay time of 1 min reduced efficacy to 20%. Especially the change of the decay time had s trong influence on the mortality achieved. Presumably this effect can be linked to appearance and of gas bubbles and mechanical destruction of cell membranes and organs due to quick expansion.