Killing Effect of Mixed Fumigation of Phosphine and Carbon Dioxide on Eggs of Lasioderma serricorne F.

Tao PENG，Shiwei LlU，Lin TAN，Xingjiang YU，Nianmei GUO

1.Nanping Entry-Exit Inspection and Quarantine Bureau of the People’s Republic of China，Nanping 353000，China；

2.Hunan Hua Wang Fumigation Disinfection Co.，Ltd.，Changsha 410014，China；

3.College of Plant Protection，Hunan Agricultural University，Changsha 410128，China

Killing Effect of Mixed Fumigation of Phosphine and Carbon Dioxide on Eggs of Lasioderma serricorne F.

Tao PENG1*，Shiwei LlU2，Lin TAN3，Xingjiang YU1，Nianmei GUO1

1.Nanping Entry-Exit Inspection and Quarantine Bureau of the People’s Republic of China，Nanping 353000，China；

2.Hunan Hua Wang Fumigation Disinfection Co.，Ltd.，Changsha 410014，China；

3.College of Plant Protection，Hunan Agricultural University，Changsha 410128，China

［Objective］This study aimed to investigate the killing effect of mixed fumigation ofphosphineandcarbon dioxide oneggsofLasiodermaserricorneF.［Method］The outside-storage phosphine generator was placed in a tabernacled smoke box，and the mortality rates of L.serricorne F.eggs in the smoke box under conditions of different aluminium phosphide usage amount and different fumigation time were studied.In addition，the times needed by tabernacle and smoke box center to reach the phosphine concentration peak were recorded.［Result］The optimum conditions for killing the eggs of L.serricorne were as follows:temperature of（27± 2）℃，relatively humidity of（45±5）%，aluminium phosphide usage amount of 1.5 g/m3and effective exposure time of 96 h.The killing effect of mixed fumigation of phosphine and carbon dioxide was increased with the extension of fumigation time.The increased usage amount of aluminium phosphide showed no significant effect on killing effect.The tabernacle space and smoke box center all required relatively short time to reach the phosphine concentration peak.If the tabernacle had a good airtightness，the overall fumigation time could be shortened.［Conclusion］The fumigation method is reliable，and it can be used for the control of L.serricorne F.in tobacco storage.

Mixed fumigation of phosphine and carbon dioxide；Lasioderma serricorne F.；Egg；Fumigation time；Mortality rate

P hosphine fumigation is the most widely used insecticidal method for various tobacco processing enterprises during tobacco storage period.Related researches have shown that carbon dioxide can enhance the penetrability of phosphine，making phosphineuniformly distributed in the fumigation space［1］.In addition，carbon dioxide can stimulate the breath of insects，thereby enhancing the killing effect on insects［2］.To improve the fumigation effect，shorten the fumigation time and reduce phosphine’s deflagration risk，mixed fumigation of phosphine and carbon dioxide for killing insects in stored tobacco has been promoted in many areas. However，there are rare reports on killing effect of mixed fumigation of phosphine and carbon dioxide on insects.

L.serricorne F.is one of the main pests in tobacco at the alcoholization stage.The mortality rate of eggs of L.serricorne F.is an important indicator evaluating fumigation effect.In this study，under the conditions of different fumigation time and concentration of phosphine-carbon dioxide，the mortality rates of eggs of L.serricorne F. were detected.The studies on relationships between fumigation time and concentration of phosphine-carbon dioxide and mortality rate of L.serricorne F.eggs will provide certain theoretical basis for determination of usage amount and time of phosphinecarbon dioxide mixed fumigation.

Materials and Methods

Materials

Overview of test site and smoke box The test was conducted in thetobacco storage in Xinshao，Hunan. The specification of smoke boxes was 1 136 mm×725 mm×720 mm.The smoke boxes were made of corrugated paper without liner，and they were filled with compacted tobacco laminas.

Test pest and reagents The 2-dayold L.serricorne F.eggs were provided by the Henan University of Technology.The used reagents included 56% aluminum phosphide tablets（ShandongShengpengTechnology Co.，Ltd.）and carbon dioxide gas（Changsha Changgang Gas Co.，Ltd.）.

Test instruments The outside-storage phosphine generator was produced by the Changsha Boiler Factory Co.，Ltd.The testing instruments included phosphine detector（HL-200-PH3，0-1 000 ml/m3）and phosphine alarm （HL-210，0-200 ml/m3）.The former was used for the determination ofphosphine concentration inside tabernacle，while the latter was used for detecting phosphine in the workplace.

Methods

Treatments Totalthree usage amounts of aluminium phosphide were arranged，including 1.5，2.0 and 2.5 g/m3.Under the condition of phosphine concentration higher than 200 ml/m3，total three fumigation times were arranged，including 48，72 and 96 h.Thus，total 9 treatments were designed，and there were 3 replicates for each treatment.

Stacking and sealing of tobacco stacks A total of 27 tobacco stacks were stacked together，and they were sealed with polyethylene film and adhesive tape.The tabernacle had a volume of about 60 m3.In the tobacco stack，the temperature was maintained at（27±2）℃，and the relatively humidity was maintained at（45±5）%.

Placement of pest eggs There were 50 L.serricorne F.eggs in each tobacco stack.The 50 L.serricorne F. eggs in each tobacco stack were placed in an open glass tube，in which there was enough tobacco leaves.The mouths of the glass tubes were sealed tightly with 200-mesh screen.The glass tubes were numbered and placed in the second-layer tobacco boxes of the stacks.In each tobacco box，the glass tube was 10 cm far from the top surface，and 10 cm far from the smoke box wall.In addition，in the smoke boxes with similar environment and situations，three blank tubes（control）were placed.

Placement of air sampling pipes

One smoke box at the center of each stack was selected，and one hole was punched with a steel pipe from the side to the center of the tobacco box. Along the hole，one gas sampling pipe was inserted to the smoke box center. The space between the sampling pipe and smoke box was sealed with adhesive tape.Thus，the phosphine concentration at the smoke box center could be detected.Another gas sampling pipe was fixed outside each tobacco stack，and it was at the same height with the central gas sampling pipe.It was used to detect the phosphine concentration inside the tabernacle.In each tobacco stack，the other ends of both the two gas sampling pipes were all placed outside the stack，and their mouths were sealed with adhesive tape.

Application of drug The drug was applied according to YC-301-2009. The mass ratio between aluminium phosphide and carbon dioxide was controlled within 1∶16.

Monitoring of phosphine concentration The phosphine concentrations in smoke box center and tabernacle space were detected once every 0.5 h within 12 h after the drug application.And then，the concentrations were monitored once every 2 h.Under the condition of phosphine concentration at the smoke box center higher than 200 ml/m3，once the expected time was achieved，the tabernacle was removed for releasing gas.The monitoring was conducted till the releasing of the tabernacle.

Determination of mortality rate of L.serricorne F.eggs After the fumigation ended，the eggs were transferred from glass tubes to petri dishes. In the petri dishes，certain amounts of wet tobacco leaves were placed.Subsequently，the petridishes were placed in an artificial climate box with temperature of 30℃and relative humidity of 70%.The hatching conditions of the eggs were observed for 14 consecutive days.

Table 1 Mortality rates of L.serricorne F.eggs in various treatment groups

Results and Analysis

Mortality rate of L.serricorne F. eggs

The mortality rates of L.serricorne F.eggs in the three control groups ranged from 2%to 4%.They were only treated as references，but not for correction.As shown in Table 1，under the condition of same drug application amount，the longer the sealing time was，the higher the mortality rate was.Under the condition of same sealing time，with the increase of drug application amount，the mortality rate of L.serricorne F.eggs did not change significantly.At the sealing time of 48 h，the mortality rate of L.serricorne F.eggs at the application amount of 2.5 g/m3was even lower than those at the application amounts of 1.5 and 2.0 g/m3，which might be caused by different application patterns.During the application process，the flow rate of carbon dioxide was high，but the generation rate of phosphine was low.In the early stage of fumigation，carbon dioxide concentration in the fumigation space was higher，leading to closed valves of eggs.Thus，although the phosphine concentration in the late period reached 200 ml/m3，and the relatively high phosphine concentration was maintained for 48 h，L.serricorne F. eggs still inhaled less phosphine gas. This explained lower mortality rate ofL.serricorne F.eggs at higher drug application amount.

Table 2 Changes in phosphine concentration in tabernacle space and smoke box center

Changes in phosphine concentration

The times needed by smoke box centers and tabernacle spaces in the 9 treatment groups to reach their peak phosphine concentrations were shown in Table 2.After 1 h，the phosphine concentration in the tabernacle space reached the peak，which was brought forward more than 1 d compared with the natural deliquescence method［3-5］. The phosphine concentration at the smoke box center reached the peak about 3 h after the phosphine concentration in the tabernacle space reaching the peak，but it was still brought forward more than 1 d compared with the natural deliquescence method［3-5］.

Discussion and Conclusions

In this study，under the condition ofsame sealing time，the usage amount of aluminium phosphide showed no significant effect on mortality rate of L.serricorne F.eggs.Under the condition of same usage amount of aluminium phosphide，the killing effect on L.serricorne F.eggs was increased with the increase of sealing time. Underthe condition ofaluminium phosphide usage amount of 1.5 g/m3and effective sealing time of 96 h，the killing effect of mixed fumigation of phosphine and carbon dioxide on L.serricorne F.eggs was best.Due to the restriction of experimental conditions，the effect of longer sealing time on mortality rate of L.serricorne F. eggs was not studied.However，in theory，the longer the fumigation time was，the better the fumigation effect was.

The outside-storage phosphine generator was adopted for the phosphine-carbon dioxide mixed fumigation.Compared with the natural deliquescence method，the times required by tabernacle space and smoke box center to reach the phosphine concentration peaks were greatly reduced.There are mainly two reasons. First，aluminium phosphide reacts quickly with the water in the outsidestorage phosphine generator，leading to rapid generation of phosphine.However，in the naturaldeliquescence method，aluminium phosphide absorbs moisture from the air slowly，thus the complete reaction of aluminium phosphide requires longer time.Second，with the outside-storage phosphine generator，phosphine and carbon dioxide are pressurized into the tabernacle space combinedly，greatly improving the penetrability of phosphine gas into smoke box and tobacco.

The mixed fumigation of phosphine and carbon dioxide has higher requirement for airtightness of fumigation environment.In real life，if phosphine-carbon dioxide mixed fumigation is adopted，the airtightness of fumigation environment must be inspected carefully.If the airtightness of fumigation environment cannot meet the requirements，the usage amount of aluminium phosphide must be increased on the premise of preset sealing time. Otherwise，the effective fumigation time can be ensured by increasing administration amount and time of aluminum phosphide.

Coresta set a series standards for fumigation of non-resistant pests and resistant pests in stored tobacco in October，2013［6］.For non-resistant pests in stored tobacco，phosphine concentration in smoke boxes should be maintained higher than 300 ml/m3for 6 consecutive days at the temperature of 16-20℃，and should be maintained higher than 200 ml/m3for 4 consecutive days when temperature is higher than 20℃.For resistant pests，phosphine concentration in smoke boxes should be maintained higher than 300 ml/m3for 12 consecutive days or higher than 700 ml/m3for 10 consecutive days at the temperature of 20-25℃，and should be maintained higher than 300 ml/m3for 12 consecutive days or higher than 600 ml/m3 for 6 consecutive days when temperature is higher than 25℃.Whether Coresta’s fumigation standards are applicable to phosphine-carbon dioxide mixed fumigation still needs further study and exploitation.

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［5］PENG ZW（彭智伟），WEN LZ（文礼章），PENG T（彭涛），et al.Killing effects of phosphine on Lasioderma serricorne larvae and eggs（磷化氢对烟草甲幼虫和卵杀虫效果实验）［J］.Anhui Agricultural Science Bulletin（安徽农学通报），2008，14（11）:201-245.

［6］CORESTA.Phosphine fumigation parameters for the control of cigarette beetle and tobacco moth［EB/OL］.http:// www.coresta.org/Guides/Guide-No02-Fumigation_Oct13.pdf.

Responsible editor：Tingting XU

Responsible proofreader：Xiaoyan WU

磷化氢-二氧化碳混合熏蒸对烟草甲虫卵灭杀效果研究

彭涛1*，刘师伟2，谭琳3，余兴江1，郭年梅1
（1.南平出入境检验检疫局，福建南平353000；2.湖南华望熏蒸消毒有限公司，湖南长沙410014；3.湖南农业大学植物保护学院，湖南长沙410128）

［目的］考察磷化氢-二氧化碳混合熏蒸法测定其对烟草甲虫卵的杀灭效果。［方法］使用仓外磷化氢发生器对帐幕烟箱中的烟草甲虫卵采取磷化氢-二氧化碳混合熏蒸法杀虫，测定不同磷化铝使用量和不同熏蒸时间条件下烟草甲虫卵的死亡率，同时测定帐幕空间和烟箱中心磷化氢浓度达到峰值的时间。［结果］帐幕温度在（27±2）℃，RH（45±5）%时，磷化铝在1.5 g/m3的使用量下，有效密闭96 h，对烟草甲虫卵有较好的杀灭效果。磷化氢-二氧化碳混合熏蒸杀虫效果随熏蒸时间的延长而提高，磷化铝用量的提高对杀虫效果的影响不明显；帐幕空间和烟箱中心磷化氢浓度在较短时间内即达到峰值，在帐幕气密性良好的情况下可缩短整体熏蒸时间。［结论］该法可靠，可用于烟仓中烟草甲虫的防治。

磷化氢-二氧化碳混合熏蒸；烟草甲；卵；熏蒸时间；死亡率

彭涛（1981-），男，湖南邵阳人，硕士，主要从事植物检疫等相关工作。*通讯作者，E-mail：25330207@qq.com。

2015-10-29

*Corresponding author.E-mail:25330207@qq.com

Received:October 29，2015 Accepted:November 30，2015

修回日期 2015-11-30