Publications

Alternatives to methyl bromide for pest control in flour mills

HGCA PROJECT REPORT 329

ALTERNATIVES TO METHYL BROMIDE FOR PEST CONTROL IN FLOUR MILLS

by

C H BELL, S T CONYERS, D A COOK, N SAVVIDOU AND T J WONTNER-SMITH
of Central Science Laburatory, Sand Hutton, York YO41 1LZ

and D BARTLETT, of
ADAS Boxworth, Battlegate Road, Boxworth, Cambs. CB3 8NN

February 2004

Abstract

Potential methods of using heat to disinfest flour mills were investigated. The effect of high temperatures was assessed against ten pest species of flour and flour mills, Ephestia kuehniella, Tribolium castaneum, T. confusum, Cryptolestes turcicus, Ptinus tectus, Sitophilus granarius, Gnatocerus cornutus, Tenebrio molitor, Liposcelis bostrychophila and Acarus siro, in the presence and absence of modified atmospheres and inert dusts. Temperatures in excess of 47°C held for 24 h, or 44oC held for 48 h, killed all stages of all the above mill pests. The presence of up to 30% carbon dioxide in the atmosphere did little to reduce target temperatures or treatment times, but the efficacy of inert dust treatments was significantly enhanced above 30oC achieving complete control of flour beetles and grain weevils within 24h at 40oC at dosages down to 1 g/m2.

Following pilot trials establishing structural component heating rates, maximal non-dust-entraining air movement rates and atmosphere leakage rates, electrical heating of air in flour mills was accomplished using multiple commercial 18 kW 3 phase fan heaters distributed throughout the building. Insect activity is greatly stimulated by increasing temperature and pests tend to emerge from harborages. For effective kill floors need to have become hot enough to kill any insects falling out of refuges in plant and upper structures. However basement floors are the hardest part of a structure to heat.

To enable the heat requirement for practical heating trials in mills to be calculated, a computer model was developed to find an air temperature to simultaneously balance heat flows through up to 10 different types of structure bounding a given volume. The model can predict the surface and internal temperatures of structural elements and can simulate the thermostatic control of the heaters and heat mats. It can also predict energy costs.

To provide the extra heat input required for wall floor joints, silicone rubber electric heating mats were placed in the ground floor area prior to the main air heating period while the mill was still running. This reduced the down-time of the mill for the treatment. Mats were covered with insulation and held in place with sand snakes. When air heating was started, additional floor fans were positioned to blow warm air over ground floor slabs to accelerate their heating and insulation was removed from the mats. The heating of upper floor wall floor joints was accomplished using fans and perforated polythene ducts fed from an available 18 kW heater. The trials demonstrated that with sufficient heaters and local knowledge of trouble areas, mills could be safely disinfested, but costs did exceed those for fumigation.

HGCA Project Number: 2301
Price: £10.75

Related Publications

Document download

View a printer friendly version of this publication

Download this publication PDF

PR329.pdf

File size: 1MB
Project_report_thumb