With the intensification of the globalization of trade, the number of import and export goods in countries around the world is increasing. Countries have also paid increasing attention to how quarantine treatment can prevent the spread of pests. Current methods of plant quarantine pest removal include fumigation, chemical spray, irradiation, cold, and heat treatment. In these methods, fumigation treatment, especially vacuum fumigation, is the main method for quarantine treatment of plants and plant products in many developed countries. 2. However, China's current fumigation and quarantine treatment methods are still relatively backward, and most of them use atmospheric fumigation. This treatment method has many disadvantages such as long fumigation time, poor safety, and low efficiency. China started the vacuum fumigation experiment as early as the 1970s, but it has remained at the experimental stage, and there are no large-scale, ready-to-use complete sets of equipment. 4~ 'The current acceleration of import and export trade and quarantine processing methods lags behind. The contradiction becomes more and more prominent.
In view of this situation, we have designed and developed our own vacuum cycle fumigation equipment and used warehouse pests and stem pests as test materials to verify the effectiveness of the equipment and technology through experiments.
-65 vacuum cycle fumigation equipment from the fumigation library (2, 65m3 in volume), vacuum pumping system, and pesticide application system 1:2002 - contact author.
System and circulation system. Its basic working principle is to use a water ring pump and a vacuum pump to pump a fumigation store placed in a fumigated cargo to a predetermined degree of vacuum, and then apply the drug and begin hermetic fumigation. After the fumigation is over, the drug is introduced into a storage tank for storage or introduced into another fumigation tank for further fumigation and recycling. This article is based on the results of the device's killing experiments on warehouse pests.
1 Materials and methods 11 Methyl bromide (CH3Br) (Linhai Jianxin Chemical Plant) 12 For test species 13 Fumigation materials and instruments Wheat and corn (Supplied by Beijing Dongjiao grain warehouse) ZXX-65 Vacuum cycle fumigation equipment (Beijing Immigration Inspection Quarantine Bureau, Beijing Instrument Factory, Beijing Huaxia Jia Vacuum Equipment Manufacturing Co., Ltd. jointly developed, see); RA fumigation gas detector (Beijing Zixin Taihe Technology Co., Ltd.) temperature and humidity meter (Changchun Meteorological Instrument Factory) electronic floor scale (Jiangsu Changzhou Wande Balance Instrument Factory).
14 Experimental methods A variety of test insects were successively fumigated according to different fumigation pressure (4/claw 3, 608/claw 3) and time (2 匕, 3 匕) combinations. The pressure was gradually increased and the concentration gradually decreased in the order of the combination. Gradually shortened order. In addition, according to the actual situation to do some 1.5h, 2h time gradient experiments. Each combination was repeated 3 times and a control without drug fumigation was set.
15 Experimental Procedure 151 Put the fumigant (wheat, corn) into the fumigation equipment to be smoked.
15.2 Store the tested warehouse pests in an Erlenmeyer flask and seal them with nylon gauze (each test insect is distributed in 3 Erlenmeyer flasks, each with 30 test worms) buried in a 5000 ml desiccator equipped with wheat or corn. bottom.
3 Record the temperature and humidity changes of the fumigation process by putting the temperature and humidity meter into the fumigation equipment.
1.5.4 Energization Turn on, close and lock the garage door and pump the fumigation equipment to a predetermined degree of vacuum (fumigation pressure).
5 Apply the corresponding weight of methyl bromide at the set dose, begin fumigation, and record the time. Record differential pressure before and after application, pressure difference before and after fumigation.
156 After the set fumigation time is reached, the pressure in the fumigation equipment is pumped to below 3000 Pa, and then the air pressure is restored to normal pressure. The library door is opened and the test worm is removed.
157 Check the insecticidal effect. For storage pests, the death rate was calculated immediately after the end of the fumigation (at the time of death) and at 2h and 24h after the end of the fumigation. The determination of the death of the worm is based on the observation of whether the body's feet or antennae of the larvae have tremors or not. The worms are determined to be dead and placed in the incubator to continue observation to verify whether there is any recovery.
2 Results and Analysis Table 1 shows the fumigation mortality rates of stored pests. Based on the analysis of the results, the optimal combination of fumigation conditions for the various insect species tested can be determined (Table 2). The so-called optimal combination is to use as few chemicals as possible (short of time) in the shortest possible time (saving time). Environmental protection) To achieve 100% insecticidal effect under the highest possible pressure (provincial equipment, energy saving).
Table 1 Warehousing insect pest fumigation mortality rate (24h) General table fumigation pressure dose amount of fumigation time (h) temperature (C) humidity corn elephant rice elephants Piguidae yellow mealworms sawn Valley Piggy Valley fool 2 65 vacuum cycle fumigation equipment continued Table Fumigation Pests Optimal Fumigation Conditions Combination Insect Fumigation Pressure Optimum Fumigation Conditions Combination Fumigation Time Re-distillation Concentration (/fumigation Pressure Optimum Fumigation Condition Combination Fumigation Time Insect Fumigation Concentration (/m3) Chimpanzee Pirates Corn Taenia Tenebrio Rice As can be seen from Table 2, the ZXX65 vacuum cycle fumigation equipment can kill all kinds of test pests in 2 hours, reflecting a fast, efficient, environmentally friendly, safe and economical design concept.
The results showed that the optimum fumigation conditions for different insect species varied. For warehouse pests, due to the same fumigating medium (corn, wheat), the difficulty of fumigation depends mainly on the strength of the insect's own resistance. From the statistical results, it can be seen that Tenebrio has the highest lethal fumigation conditions, followed by glutinous rice husks and sawn gorillas, and the corn elephants, rice elephants, and red rice cultivars are the lowest. At the same time, several warehouse pests tested at the same concentration, Under the condition of time, the insecticidal effect under the pressure of 5000Pa is not as good as that under the pressure of 10000Pa and 20000Pa (see Table 1). From an economic point of view, when using the ZXX-65 vacuum cycle fumigation equipment to fumigate food, it is recommended to use a 2h combination of fumigation conditions to ensure that various storage pests in the grain are killed.
It can be seen from the mortality rate 24 h after fumigation of the storage pests that, with the same fumigation pressure, the application amount (increasing the fumigation concentration) is better than the fumigation time; when the fumigation time is the same, the fumigation concentration is increased. The degree of vacuum (reducing the fumigation pressure in the warehouse) has a good effect; in the case of the same fumigation concentration, the fumigation time is better than the vacuum degree. This shows that in the three factors of fumigation pressure, fumigation time and fumigation concentration, the fumigation concentration plays the largest role in killing pests, followed by fumigation time and fumigation pressure.
According to observations, the larvae that were determined to be dead when the mortality rate was counted were all blackened and rotted after being placed in the incubator, and there was no recovery phenomenon. This is very different from the phenomenon of resuscitation of pseudo dead bugs that can be observed in conventional fumigation. On the other hand, it illustrates the reliability of the effect of vacuum drug fumigation.
3 Discussion In the statistics of mortality, there are occasionally occasions where there are differences in the repeated results of the same combination of fumigation conditions. The reason may be that there may be weather conditions (temperature, humidity) or fumigant materials ( (Different moisture content) or artificial statistical errors. At the same time, it can be observed from the statistical results that under the same conditions of pressure and drug dose, some long-term fumigation results are not as good as short-term, such as the fumigation of Mixiang 5000Pa60g/m3, 3h, and the mortality rate at that time was lower than that of 5000Pa 2h. The reasons for this need to be further studied. However, from the 24h statistical results, under the same conditions of pressure and dose, mortality and fumigation time are proportional to each other, there is no special phenomenon.
Acknowledgments Li Deshan and Liu Ruixiang of the Beijing Entry-Exit Inspection and Quarantine Bureau gave great care and guidance to this study and expressed their deep gratitude. Ru Lin's comrades from the Inspection and Quarantine Disinfection Processing Center of Beijing assisted in the research of this subject and expressed their gratitude.
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