Alternatives to Methyl Bromide; IPM in three typical danish flour mills 4. Discussion4.1 IPM in mills 4.1 IPM in mills IPM is useful in mills The actual investigation supports the view that the IPM concept is very useful in the milling industry as an alternative to fumigation’s with methyl bromide. The use of the different elements recommended for an effective IPM programme will always be dependent on their relevance as experienced by the mill. Careful control of incoming grain is a procedure that is recommended in IPM programmes, but as Danish mills do not encounter problems with insect pests in grain storage, they show reluctance to increase their efforts in this area. This fact is also applicable to other components of IPM in mills. Shutdown The purpose of shut downs of the production in the mills, together with cleaning procedures, is most relevant. The experience from the Danish mills shows that the mills manage the ban against methyl bromide primarily by increasing their sanitation programmes. HACCP The HACCP (Hazard Analysis Critical Control Points) concept was developed in order to manage contamination of food, especially microbiological contamination, through the establishment of hazard analysis and critical control points. It yields a logical and cost-effective basis for a better decision-making with respect to product safety (Leaper, 1997). Although it seems extremely difficult to establish a full HACCP investigation on insect pests in mills, it could form a relevant framework for further improvement of the IPM system. By operating with a team of experts, who continually try to improve the methods used in prevention and control of pests, a system that can effectively react to changes in pest population is created. Similar co-ordinated strategy has proven successful in other food plants (Stanbridge, 1998). It has been argued that a zero level of insect tolerance ought to be a demand before IPM is implemented (Hellekant, 1995). Although certainly an advantage, the situation in the Danish mills show that a zero level is not needed, before the mills can operate with and benefit from the introduction of IPM systems. 4.2 Weaknesses in the actual programmes The most pronounced weakness in the actual programmes is the inability to make a proper evaluation of the effectiveness of the IPM systems. Due to its nature and the lack of accurate monitoring of T. confusum, this species is considered to be the most problematic pest species in the three mills. The monitoring and control of pests in Danish flour mills is left in the hands of a PCO. The collaboration between the mills and the PCO is a critical point and constituted during part of the trial period a bottleneck in the actual systems. It is a clear condition of a well-acting IPM system that the co-operation between the two partners is perfect and that the expectations of one another are well defined. The relationship between the mills and the PCO was later improved, and it must always be an aim to ensure that this relationship be further is improved. Further the pest control needs to be more targeted towards preventative measures and conscious alertness on well defined action levels. The results from inspections and trap catches are now to some extent used as a measure, which indicates if pest populations have increased in the past. The systems could be improved if the mills tried to introduce action levels and further decided what to do when these levels are exceeded. Although not a perfect way, such a step could be a way to improve the actual systems. None of the mills is carrying out a detailed control for insect pests on the tailings from the final sifters. Therefore an internal infection in the milling machinery can increase gradually and first be noticed when the pests enter the production area. 4.3 Recommendations to the mills Control on sifters The following recommendations can together with the general recommendations in section 4.4 be given to the mills. It seems essential that the mills establish permanent and detailed control on materials from the sifters. The sifters are the most relevant control points in the mills. This will yield a good measure of the degree of infestation inside the machinery. This control must include establishment of thresholds and a decision on what to do if these thresholds are exceeded. Collaboration The collaboration between the mills and their PCOs needs to be improved. Situations where the PCO together with the staff at the mill are making a detailed investigation on a specific pest problem always seem to produce valuable results. Internal procedures It can be recommended that the internal procedures be tightened. Many procedures against insect pests are in use but every now and then these procedures fail, e.g. when sacks with material are left in the mill, inspection and cleaning are postponed etc. Further there is a need to establish control on the flour silos in mill 3. Building structure The building structure is now and then important for the pest problem. It is essential that personnel with pest experience are include at an early stage when new building structures or alterations are planned. 4.4 General recommendation on IPM in mills On behalf of the two Danish projects (Part 1 & 2) the following main recommendations can be made. Inspection frequency The mills need to decide in advance what to do when an increase in the catch of E. kuehniella is occurring. The actual systems are designed in such a way that the traps will be inspected every month but in a situation where trap catches increase rapidly and counter steps are needed, a quicker response could be valuable. This would require that either the PCOs increase the inspection numbers when necessary or that the mills train their personnel to do the job. Cleaning inside machinery Shutdown in production together with cleaning can be recommended. Very satisfactory results are obtained from mill 1 (4-hour suspension each week) and also from mill 2 (2-day suspension three to four times a year). The experience from the largest mill (3-4-day suspension three to four times a year) is less positive, the separation and assembling of the sifters turned out to be more difficult and time-consuming than expected. From a theoretical point of view it seems that three to four annual shutdowns together with cleaning of the whole mill would be sufficient for a break in the build-up of pest populations under the climatic conditions present in Danish flour mills. Relationship between pest and complaints It can be recommended that a detailed investigation on the relationships between pest occurrence and complaints be carried out in order to analyse the effect of the steps taken against the pests. Tribolium At a more superior level it seems relevant to point out the need for more scientific research on the possibilities of monitoring Tribolium species in mills. The commercial traps for T.confusum are not effective in Danish flour mills, and the monitoring success during inspection is also variable, and finally an inspection requires time in order to be successful in the identification of breeding size.
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