A very large (covering more than a hectare) modern complex in northern Australia had a problem with beetles and their frass appearing on tablecloths when they were set for functions. The beetle was small, reddish-brown, covered with fine hairs, oval shape with no visible head when viewed from above.
So the beetle is the cigarette beetle, Lasioderma serricorne. Now that makes it easy – this is a well known stored product pest that attacks tobacco, rice, oilseed, herbs, cocoa, dried fruits, nuts etc. So find the source – which by the numbers found and the area they were covering must be large – remove it, treat and problem solved.
But a search of the kitchen did not turn up any infested product. There appeared to be nothing else that would harbour these pests. The facility was barely a year old. So what is the source and how do you explain the very obvious frass on the tablecloths?
The first task is to find the source of the infestation.
The frass on the tables was the clue. The very high ceilings were the source! A knowledge of building products and structures is important for general pest work as well as termite management.
The ceiling product used on this project and on many large facilities is produced by applying heat and extreme pressure to straw. The finished product contains only straw, paperboard and non-toxic PVA glue. The sales pitch states – “A natural construction solution from recovered agricultural by-products. No preservatives, microbicides or any other additives are used.”
These panels have become a product of choice for many large stadiums, convention centres and school halls because they are seen as environmentally green, are tough, termite and rodent resistant, can be easily installed in large sections and their acoustic and thermal insulation attributes. Apart from large projects they are also used as office dividers through to kit homes.
The ceiling product was sandwiched between the iron roof above and masonite with holes below. The beetles and the frass were falling through the holes in the masonite. In the two cases that have presented recently it is known that the straw ceiling product was drenched before installation.
So how do you treat a hectare of ceiling product sandwiched between iron and masonite?
There were many suggestions. These included:
- Do nothing.
- Remove and replace the ceiling.
- Place a physical barrier or spray lacquer over the holes to stop the frass dropping out. This would not stop the infestation or damage.
- The most effective treatment would be fumigation. This is not practical due to construction of the building and political reasons.
- Dichlorvos injected into the holes in the masonite below the straw panels – a huge task (panels cover over one hectare) and risk of affecting a sensitive person.
The simplest solution for the future would be for the company to impregnate the product with insecticide at manufacture and for the builders to ensure it remains dry during installation .... but we can all dream.
What would you recommend?
The cigarette beetle infestations were thought to be confined to certain areas. These were probably the panels that were drenched between delivery to the site and installation. However, the panels could not be easily inspected directly for moisture level, damage or infestation.
Cigarette beetles are strong fliers. Russell X-lure pheromone traps are very effective at trapping moths and cigarette beetles. These should be placed below the ceiling at one per 100m2 throughout the complex to determine the major areas of infestation and checked every six weeks and results recorded.
Chemical treatment – we now know what the insect is and where it is and that the source is cannot practically be removed. Any chemical treatment will be management rather than elimination so it will need to be on-going. Most of the areas these panels are used are open to the general public so a chemical with no odour registered for stored product pests should be chosen. If a spray or dust is applied into the holes it will simply run/fall out the same hole. The recommended treatment method is a mist injected into the infested straw panels.