Infestation

Page 1

DEFRA's Approach to Pest Risk Analysis

Plant pests include insects, bacteria, fungi, viruses & other pathogens.

Pest Risk Analysis (PRA) is "the process of evaluating biological or other scientific & economic evidence to determine whether a pest should be regulated & the strength of any phytosanitary measures to be taken against it".

PRAs vary in length from single expert judgements to long assessment documents of biological factors, climates, costs and benefits of keeping a pest out an area.

UK uses a short and more detailed scheme from the European and Mediterranean Plant Protection Organisation (EPPO).

PRAs give a snapshot of the analysis at a particular time & may go out of date as new informations comes to light.

New pests in England or Wales must be reported to Plant Health and Seeds Inspectorate.

PRA can conclude that the risk of some organisms is low and doesn't need to be excluded or eradicated.

Offence under Section 14 of Wildlife and Countryside Act 1981 for any person to release or allow to escape any wild animal that's not a regular visitor to Great Britain.

Precautionary approaches and judgement is made on organisms where data is lacking, inconclusive or contradictory.

DEFRA's PRAs focus on risk to the UK and EU.

Rules on imports and movement of plants is managed by the EU's Standing Committee on Plant Health who take account for the risks of a pest and the costs of risk management measures across the EU.

Recognising Wood Rot & Insect Damage in Buildings

Wood rot is durable and resistant to most biological attack if it remains dry.

Most cases arise from rainwater entering the fabric of the building or rising damp.

Pre-Inspection Procedure

Establish with client extent of inspection required.

Establish with the client the age and history of the building and any previous maintenance/repair work.

Ask for previous wood treatment specialist surveys.

Ensure the inspections for fungal & insect attack are carried out simultaneously.

Areas at Risk

Skirting on damp walls.

Bearing ends of timber in non-cavity walls.

Incorrectly positioned vapour control layers.

Wall plats

Wood laid over solid floors

Timber components in cellars & basements

Symptoms of Wood Rot

Loss in strength, softening or disintegration of wood

A hollow sound

Wood discolouring in patches or streaks

Fungal mycelium

Distinctive mushroom smell

Presence of certain wood boring insects.

Symptoms of Insect Infestation

Holes in surface of wood with clean sharp edges.

Bore dust ejected through holes, forming small piles beneath.

Tunnels beneath the surface.

Larvae found by probing.

Surface irregularities (bumps & corrugations)

Wood Rot Fungi

Wood rot fungi cannot utilise wood at or below 20% moisture content.

Presence indicates damp conditions exist.

2 Major Groups - Brown Rots and White Rots, collectively known as Wet Rots (except for one brown rot).

Brown Rots - cause wood to become darker in colour and crack along/across the grain - dry wood will crumble to dust.

White Rots - cause wood to become lighter in colour & fibrous in texture with no cracking.

Same remedial measures are required for all types of wet rot.

Dry Rot (Serpula Lacrymans) - mostly found in softwood and causes extensive damage, turns woods dark brown and cracks along/cross the grain and causes it to crumble.

Wet Rot

Remedial Treatment of Wet Rot

Establish size & significance of attack.

Size is closely linked with extent of wet areas.

Locate and eliminate sources of moisture.

Promote rapid drying of structure by increasing airflow & using dehumidifiers.

Introduce support measures for ventilation or providing barriers to moisture.

Remove all rotted wood by cutting away timber.

Use preservative pretreated timbers in replacement work.

Dry Rot

Often regarded as 'cancer' of a building.

Favours dark, damp & stagnant conditions to develop.

All wood destroying fungi requires water for germination, growth & survival.

Wood must have a moisture content in excess of 28-30% to initiate growth.

Growth rates of p to 4m/year have been recored, BRE gives a figure of 0.8m/year as the maximum growth rate.

Identification of Dry Rot

Wood shrinks, darkens & cracks in 'cuboidal' manner.

A silky grey mushroom coloured skin with patches of yellow develops.

White fluffy cotton-wool like mycelium developed.

Strands develop in the mycelium which are brittle, dry and crack.

Rust red coloured spore dust frequently appears around fruiting bodies.

Active decay produces a musty, damp odour.

Remedial Treatment for Dry Rot

Establish size & significance of attack.

Size is closely linked with extent of wet areas.

Locate and eliminate sources of moisture.

Promote rapid drying of structure by increasing airflow & using dehumidifiers.

Introduce support measures for ventilation or providing barriers to moisture.

Remove all rotted wood by cutting away timber.

Contain fungus within the wall using paints/renders and other barriers.

Apply superficial preservative treatment.

Identification of Wood Boring Insects

Number of insects, mainly beetles use wood as a food source.

Beetles have similar life cycles but vary in the type of wood they attack and the extent/type of damage they cause.

Wood boring insects found in building timber fall into 3 Categories:

Larva

Pupa

Adult

Damage Categories for Wood Boring Insects

Category A: Insecticidal Treatment Needed - deathwatch beetle & house longhorn can cause structural damage.

Category B: Treatment Required to Control Associated Wood Rot - some insects can only feed on damp wood so further infestation is prevented by remedial measures used to control wood rot.

Category C: No Treatment Needed

Identifying Beetles with Circular Holes 1-2mm Diameter

Bark Borer Beetle

Mainly dark brown & gritty bore dust present in 'bun shape'.

Damage in softwood bark edges.

Sapwood scored & penetrated by short 15mm deep tunnels.

Common Furniture Beetle

Cream dust present.

Large amounts of tunnels in random directions.

Dust feels gritty in lemon shaped pellets.

Ptilinus Beetle

Cream dust present.

Talk-like texture to the dust when rubbed between fingers.

Bore dust difficult to dislodge from tunnels.

Lyctus Powderpost Beetle

Cream dust present.

Talk-like texture to the dust when rubbed between fingers.

Bore dust easy to dislodge from tunnels.

Pinhole Borer Beetle

Damage found in new timbers.

Tunnels long, straight, unbranched, except for short side branches across the grain.

Usually darkly stained tunnels.

Identifying Beetles with Circular Holes 2mm Diameter

Dermestid Beetle

No bore dust present.

White lining to some tunnels.

Tunnels 3-4mm diameter.

Cast larval skins present.

Deathwatch BeetleGritty, disc-shaped pellet bore dust present

Bostrychid Powderpost BeetleTalc-like or powdery bore dust present.

Tenebrionid Beetle

Coarse chipping texture to bore dust.

Rotted wood.

No large tunnels 20mm diameter.

Stag Beetle

Coarse chipping texture to bore dust.

Rotted wood.

Large tunnels up to 20mm diameter.

Identifying Beetles with Oval or Irregular Holes

Wharf Borer Beetle

Wood rotted by fungus.

Large tunnels 6mm across.

Bore dust is coarse, mud-life material with clumps of coarse fibres.

Forest Longhorn Beetle

Occasional plugs of coarse fibres.

Bark-edged material present.

Sapwood surface scored.

House Longhorn Beetle

Bore dust present.

Oval tunnels & emergence holes.

Tunnels merge to form powdery mass contained by sound surface skin of wood.

Jewel Beetle

Bore dust present.

Elongated, oval tunnels with parallel sides and few emergence holes.

Characteristics of Category A Beetles (Usually Require Insecticidal Treatment)

Common Furniture Beetle (Anobium Punctatum) - Native to the UK!

Timbers Attacked - sapwood of hardwoods & softwoods.

Frequent in old furniture & constructional timbers & areas affected by damp.

Lifecycle: 3+ years

Damage - tunnelling in sapwood along the grain.

Emergence Holes - circular, 1.5-2mm diameter.

Tunnels - short, circular, 1-2mm diameter. Often extensive, random orientation but mainly in direction of grain. Often exposed on surface of floorboards.

Bore Dust - cream coloured, lemon shaped pellets & gritty when rubbed between fingers.

Remedial Treatment - usually organic solvent, micro-emulsion or paste OR smokes.

Adult Insect Characteristics - 3-5mm long, dull brown, lines of pits on wing covers. Emerge late March to early August.

Deathwatch Beetle (Xestobium Rufovillosum) - Native to the UK!

Timbers Attacked - sapwood and heartwood of partially decayed hardwoods, mainly oak.

Often found in historic buildings where structures mainly used oak & elm.

Softwood rarely attacked except when in contact with infested hardwood.

Found particularly in areas prone to dampness.

Lifecycle - 4+ years

Emergence Holes - circular, 3mm diameter.

Tunnels - circular, 3mm diameter. Often extensive, random orientation, mainly in direction of grain.

Bore Dust - cream coloured, disc shaped pellets and gritty texture.

Remedial Treatment - usually organic solvent, micro-emulsion or paste. Use pressure injection or gravity fed applications for impermeable timbers OR use smokes.

Adult Insect Characteristics - 6-9mm long, chocolate brown with patches of yellow hairs. Found from March to June.

House Longhorn Beetle (Lyctus Brunneus) - Native to the UK!

Timbers Attacked - ssapwood of most softwoods, particularly roof timbers.

Commonly found in SW of London.

Small inactive infestations common in buildings over 100 years old in London.

Larval feeding (scraping noise) may be heard in large infestations.

Lifecycle - 4+ years.

Emergence Holes - few, large, oval, 6-10mm in diameter.

Tunnels - 6-10mm in diameter, extensive & join up to cause almost complete disintegration of sapwood. Dust filled tunnels can cause blisters or corrugations on surface of wood.

Bore Dust - cream coloured with sausage shaped pellets and gritty texture. Small chips & wood fibres possibly present.

Remedial Treatment - usually organic solvent, micro-emulsion or paste.

Adult Insect Characteristics - 10-12mm long, black or dull brown, smooth central line on thorax flanked by two shiny black bumps.

Characteristics of Category B Beetles (Treatment Required to Control Associated Wood Rot)

Wharf Borer Beetle

Habitat - very damp, decayed softwoods & hardwoods.

Often found in wharf timbers & timber in freshwater or brackish conditions.

In cellars or timber that is buried.

Emergence Holes - large oval holes 6mm dimension.

Create irregular shaped galleries packed with hardened, mid-life material & plugs of coarse fibres.

Bore Dust - none present, tunnels may be plugged with small masses of coarse fibres.

Remedial Treatment - none required apart from removing source of damp & dry out sound timber.

Adult Insect Characteristics - 6-12mm long, elongated, pale reddish brown with distinctive black top to wing covers.

Characteristics of Category C Beetles (No Treatment Needed)

Forest Longhorn Beetles (Family Cerambycidae) - Native to the UK!

Timbers Attacked - imported & British grown softwoods & hardwoods.

Attack standing & felled trees & dried timber where bark is attached.

Damaged timber can be used in buildings containing larvae.

Cannot reinvest dry timber without bark.

Lifecycle - varies depending on particular Forest Longhorn.

Emergence Holes - large oval holes 6-10mm in dimension.

Tunnels - oval, 6-10 in dimension in bark and sapwood. Tunnels do not merge, usually run across the grain.

Bore Dust - none present, tunnels may be plugged with small masses of coarse fibres.

Remedial Treatment - none required apart from removal of bark.

Adult Insect Characteristics - wide ranging appearance, commonly brown or black with long antennae from kidney shaped eyes.

New Page