55.H.003

Abstract for DEFRA files (not confidential)

AFM 226 LINK Project: Developing heat treatment for pest control in mills

What the project was attempting to achieve?

The objective of the project was to develop heat treatment as a viable form of pest control for millers. To this end the distribution of heat needed to be improved and the target temperatures raised to meet the requirements by millers of a total kill of all life stages of insects within 48 hours.

To explain, with the phase-out of Methyl Bromide (used in mills as a fumigant for pest control), millers have spent over a decade looking at finding an effective alternative pest control procedure for mill structures that is both technically efficient (involves less than 48 hours mill downtime) and cost effective. A previous LINK project (AFM93) evaluated several promising alternatives to Methyl Bromide. Of the alternatives heat treatment, in combination with desiccant dusts, was most effective.

Outcomes

Despite the improvements in heat distribution and the addition of desiccant dusts during the process, neither trial was successful at killing 100% of the insects (in bioassays) at all life stages, as it was not possible to heat every part of thetrial mills to lethal temperatures, particularly the ground floors. Thus the treatment cannot be considered an ‘alternative’ to Methyl Bromide in terms of performance. Furthermore, heat treatment is only suitable for certain structures, notably it is suitable for smaller timber/ brick and concrete structures, and less suitable for steel frame clad buildings. To help millers decide whether their structure is suitable and inform them of the considerations that have to be taken in the planning of a heat treatment a decision tree was drawn up and publicised to millers.

Other findings/ important developments were:

oHeaters

The AFM93 project showed that using an external heat source was ineffective as poor circulation resulted in the uneven distribution of the heat. Attention turned to in-mill heating systems and for mill trials under this development project, specialised (ATEX compliant) ThermoNox heaters were imported from Germany and ADAS developed wall floor joint heaters.

  • Modelling techniques and insect mortality

ADAS used predictive modelling techniques to monitor the heat treatment and cool spots. CSL established the temperature tolerance of the three most common flour mill pests between 47 and 53°C at all life stages. This information was used to set target temperatures to be achieved around the mill during the trials to assess the progress of the treatment. Bioassay results confirmed the accuracy of the insect death model and the feasibility of predicting the efficacy of treatment based on monitoring temperatures within the mill. A hand-held infrared thermometer and data logging system was developed to enable real-time monitoring during heat treatment.

  • Mill machinery

Temperature records and computed insect mortality inside open and closed sifters showed that fully assembled sifters and purifiers were effectively treated in 38 hours. Unassembled sifters took only 28 hours to treat. This finding means that mills do not need to dismantle their machinery before a treatment, thus saving time.

How this treatment be taken forward?

The treatment has been advertised to millers via various media. On 18 October 2005 nabim held a heat treatment workshop which was open to the public. The decision tree (to help millers decide whether the treatment is suitable for their site) was circulated to millers and is available from nabim’s website (for members).

The treatment is currently available from Igrox, and at least one milling company has booked a treatment for 2006. Heat treatment is also being used to support another pest control treatment, fumigation with ‘Profume’.

nabim was asked in January 2006 to participate in a European Commission funded project assessing heat treatment as an alternative pest control method to Methyl Bromide and is currently consulting members on this.