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07 December 2018

The humble cuckoo wasp solves a pest-related dispute

Pest control | PPC93 December 2018

In this new PPC feature we delve into the travel diaries of John Lloyd, Technical Consultant and Entomologist at BPCA consultant member company, IPMIC, and ask him to tell us one of his ‘Consultant Stories’.

One flew under the cuckoos nest

Everyone understands the seriousness of  pest contamination of food. But sometimes the contamination of food packaging, especially in transit from one part of the world to another, can also cause grave economic and business loss to the parties.


A single cuckoo wasp (family Chrysididae), caused a food industry contamination complaint when a food company in Asia found it. The wasp was discovered on a cardboard layer sheet in a pallet of food packaging shipped from the UK to Asia.

Also known as the ruby-tailed wasp, the cuckoo wasp is strikingly attractive with its bright, iridescent red, green and blue colouration. You could easily assume this insect to be of exotic or tropical origin. However, it actually occurs worldwide and throughout the Palearctic region including Europe and Asia.

Cuckoo wasp habitat and behaviour

Cuckoo wasps have an external life cycle and are kleptoparasitic insects. They lay their eggs in the nests of other insects, especially potter wasps (eumenids). Once their egg hatches, the larva eats the host larva, then pupates and emerge as an adult.

To protect themselves from being stung by their prey during egg laying, cuckoo wasps have a tough outer body surface and can uniquely curl their body to reduce the risk of stingers penetrating their body segments. This curled up body posture is a characteristic feature to their identification.

he food company in Asia wanted to reject the consignment shipped from Europe

Problems of food packaging contamination

In the food industry, any insect contamination of food packaging by stored product insects or from ‘casual intruders’, can pose a serious risk to food safety. Such instances should be investigated, and corrective actions immediately adopted to prevent a recurrence.

Sometimes, the source of insect contamination can be difficult to establish, but it is crucial in many cases, as responsibility can prove costly for suppliers.

Consequences of insect contamination

In addition to breaching food safety standards and codes of practice, incidents of insect contamination can have a negative commercial impact on suppliers by causing strained relations between supplier and food company or the supplier may incur heavy financial penalties.

Following a contamination incident, suppliers are usually under pressure to demonstrate due diligence by immediately implementing additional preventative measures and controls. Sometimes these can be very costly.

Suppliers of contaminated food packaging may incur additional costs and face consequences such as the rejection of a pallet or rejection of a whole consignment, a reduction in future trade volume, or the loss of future business altogether, to say nothing of high profile lawsuits or significant insurance claims.

If the goods get rejected, returned or disposed of, this may cause direct financial loss for the supplier, which is especially costly if goods have been shipped abroad.

Although such costs and losses frequently occur in the food industry, the pest contractor might not be informed and may not be sensitive to these issues when assessing the control measures for a site. It is therefore essential that pest controllers follow best practice and monitor sites for non-pest species as well as the more obvious, critical pest species that are associated with food sites or with suppliers in food-related industries.

Responding to insect contamination incidents

When insect contamination incidents occur, it is essential to identify the species concerned and to thoroughly review details, dates and events to establish what has happened, where and how.
For food industry suppliers, this could help establish if the cause of contamination occurred at their site, or if contamination occurred after the goods left their factory.

The timeline and investigation

The timeline and investigation

Cuckoo wasp: case review

In the case of the cuckoo wasp, a complaint was raised, and the food company in Asia wanted to reject the consignment shipped from Europe as it believed the factory, located in the UK, to be the source for the insect contamination.

An incident review was carried out by IPMIC and details revealed where the likely point of contamination occurred.

Findings of the incident review

In February, on the day of production, the daytime temperatures were <6°C and -3°C at night.

These temperatures are too cold for cuckoo wasps to be active in the winter.

From June to September, the consignment was in Asia where the warmer summer temperatures favour cuckoo wasp activity and breeding. The warmer temperatures mean that host insects are active and breeding in warm sandy burrows, and this is when the female cuckoo wasps begin hunting for host nest sites in the ground.

The cuckoo wasps are active during warm seasonal temperatures.

Given the dates in question and seasonal changes in environmental temperature, it is likely that the point of contamination occurred in Asia.

Although not active in the winter time in Europe, cuckoo wasps would be active during the warmer summer temperatures in Asia.

Likely route of contamination

A top-cover sheet (barrier sheet) was present over the pallet to reduce the risk of insects falling or entering from above. That meant the packaging contamination, in this case, was likely to have occurred from the base of the pallet, as cuckoo wasps tend to search for their host nest burrows at ground level.
It is therefore likely that on this occasion, the insect gained access into the packaging from the base of the pallet once the consignment had arrived in Asia.


Due to the species identification and case review, the supplier in the UK was found not to be the likely source of insect contamination within the supply chain.

This cuckoo wasp incident highlights the significance of the presence of non-pest species and casual intruder insect species on food premises and in food-related industries. It illustrates the importance of excluding such pests from manufacturing or warehouse environments and demonstrates the importance of species identification in dispute resolution, as this can provide a key in determining the point or source of contamination.

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Source: Bulletin

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