|
Flour Mill Insect Control
Stored Product Insect (SPI) Control in flour and other
related mills is an important yet complex process. It requires, not only a
specialist understanding of the biology and habits of the likely pest insects,
but of the unique features of the complex flour milling process and production
requirements of an often high volume, low margin industry. Insect control post
methyl bromide is therefore complex and expensive, but still very necessary.
Such conflicting interests can often lead to millers being
acutely aware of the cost/return relationship for cleaning and pest control. This
can be a difficult balance but it is essential to get it right.
Flour and other millers can be divided into different groups
depending on the key markets they have chosen to attempt to supply. Suppliers to the Marks & Spencer / top
end of the market will be able to command a degree of premium on their product,
however in return M&S and the like demand and expect zero detectable
infestation levels, meticulous hygiene and cleaning standards supported by
appropriate full genuine documentation.
The middle, larger section of the market is devoted to
production and a pragmatic cost effective approach to insect control,
realistically sticking to the letter of their customers’ requirements and legal
requirements of food safety, but working together with their customers to
achieve “acceptable” levels of insect control and food hygiene at “the right
price”.
At the budget end of the market and in many feed mills and
some pet food providers, we still see significant insect infestations that are
not controlled properly, not picked up by EHOs and with customers purely
fixated on price. There is no concern about, or understanding of the potential
perils of shipping out infested products. I would qualify this by saying there
are some pet food and feed manufacturers whose insect control and hygiene
practices put many food manufacturers to shame!
Insect control can be divided into two stages – “Assessment”
and “Control”
Assessment stage:
1)
Where exactly is the infestation located, not in
terms of visible dead adult beetles or moth on the floor, but where are the
eggs, larvae and pupae – the core of the infestation, and in what numbers?
2)
How does the location of the infestation and
numbers of insects relate to risk to the product? - A moderate sized Rust Red
Flour beetle infestation in 2nd
BK rolls is of less immediate threat than a small infestation of Broad Horned
Flour beetle in a finished product bin, or a few mill moth on a flour packer.
3)
Where did the infestation come from and where is
it likely to spread to? – Rust Red Flour beetle are quite capable of coming
from grain – check grain monitoring systems, likewise some mix back and
sweepings can be put back into the system at 2nd BK roll stage, so
this may be the source. However they could theoretically go all the way if
conditions are right to infest the whole mill. However in many mills, they tend
not to like pure flour and Confused Flour beetle or Broad Horned Flour beetle
become dominant in the UK.
4)
What deficiencies in the mill process management
have allowed the infestation to develop? – e.g.
a) Lack of proper checking of raw materials, wheat, returns, pallets,
bags, tankers etc. b) Poor dust control or exhaust leading to external dust
problems or internal humidity problems c) Inaccessible dead spaces inside
machinery or in fabric of building d) Poor cleaning of accessible dead spaces
due to inadequate training or supervision of cleaners.
Control Stage:
Control options are;
1)
Physical cleaning and removal of harbourages and
insects, particularly moth webbing
2)
Heat treatment – Spot treatment of machinery,
rooms or silos or space treatment of whole buildings
3)
Cold contact (Cryonite)
4)
Direct insecticidal contact e.g. aerosol, mists,
fogs, “organic” sprays and substances.
5)
“Novel” insecticidal treatments such as
desiccant dusts, pheromone disruption programmes, Insect growth regulators etc
6)
Regular residual insecticidal dusts and sprays
7)
Fumigants such as sulphuryl fluoride, phosphine
or CO2.
8)
Modified conditions to inhibit breeding and
population development e.g. too dry, too hot, too cold, too physically hostile.
Integrated Pest Management in Mills
In the real world of flour production, downtime for
treatments is often limited, therefore systems of prevention and inhibition of
population development are important, and where treatments are carried out it
is important to make them as effective as possible at targeting not just adult
SPI, but importantly eggs, larvae and pupal stages which are the core of any
SPI infestation with adults just being the visible symptoms.
In the milling situation in the UK, only HEAT, PHYSICAL
CLEANING or FUMIGATION kill eggs, larvae and pupae, other control measures play
their role in disrupting or inhibiting population development by maybe killing
adults before they can mate and lay eggs, and it is the role of the pest
control biologist or manager in charge of over -seeing a flour mill IPM system
to work closely with the mill management to target and balance the finite
physical and financial resources to maximum effect.
A single annual Sulfuryl Fluoride fumigation may achieve a
good kill rate of adult insects for a
short period of time, but unlike methyl bromide, it is not a good fumigant for
killing eggs and a very high concentration
x time product is required to
have any long term effect. Sulfuryl Fluoride is a very penetrating gas, and at
high concentrations it leaks very quickly from buildings even in still
conditions, any form of wind enhances the leaking process massively and
threatens the success of the fumigation unless the gas is topped up regularly
throughout the job to maintain the required concentration inside – which can be
incredibly expensive.
Heat treatments of whole buildings can be very effective,
however, it should be noted that thick walls and floors will not heat up
sufficiently unless very long treatment times are used, and even then, a deep
crack in a concrete ground level floor will never heat up, as essentially the
energy is always being conducted away to earth.
Thermokil advocate a combination of targeted heat combined
with other treatment techniques as appropriate from the list above, depending
on the situation. Every single mill is different, and even if the mills and
infestations were identical, the approach and abilities of the mill managers will
vary between sites making some systems workable with some managers,
impracticable with others.
 
The linchpin of any treatment programme is the pest control
biologist over-seeing the treatment programme and his team, their knowledge of
the milling process and insects concerned, his specialist knowledge of the
treatment options and his ability to work with the site managers and their
staff.
For more information contact David Hammond, Managing
Director of Thermokil Ltd on 07870 562874 or at heatinsect@yahoo.com David has had 30 years of insect control
experience working in over 100 mills around the world in 12 different
countries.
|