Red Mite Trapping – The Observation Effect

Erwin Schrodinger developed a thought experiment that said “if I placed a cat in box with a radioactive atom, and the box is sealed, the cat is both alive and dead in our minds until we see it”. Red mite monitoring is a similar tool, the truth of whether you have red mite is not whether or not you think you do, its revealed when you actually monitor the situation accurately, and from there the right actions can be taken.

I remember going to a site that was having issues, it was my first time seeing this farm and when I went there I was quite clearly told “we don’t have red mite so its not that”. The very first drinker clip I looked at was covered in mite. When I said that these are definitely red mite, then I was told “they re not red, they are black”.. This made me realise very clearly that it was a failing of my side of the industry in reaching everybody with accurate information, and it informed much of what Rosehill is about now. Informing and developing tools to help increase hen performance and in turn, farm revenue.

Red mite “Dermanyssus gallinae” require a certain environment to really get to very high numbers, it’s a very specific environment that struggles to exist in a natural state year round. It must have a stable temperature of approx. 19-26◦C, the environment must be complicated enough to form colonies out of direct light and safe from being pecked at, and it must not have too much ammonia as this seems to affect levels. They also require a large number of hosts to feed on, and darkness. Funnily enough, it seems, the perfect environment for red mite seems to be a modern free range poultry shed. I have monitored red mite across every type of system in the UK for approaching 10 years and countless hours of sample examination and trap placing, and the evolution of better conditions for the hen has also led to better conditions for the mite.

A powerful thing to understand, is the red mite will take its feed at approximately 3 hours into darkness onwards. It will feed for 20 minutes and then the next port of call is mating. It’s a troubling thought, say a 16k unit will have up to 5000 a hen, and a ration 40-50% females. So during the night there are 80 million mite that have gone out for a drink and then mate, before crawling into bed for the day. Its no surprise that amongst the experts in this field they are known as the “student mite”. After 1-2 days they will lay a clutch of 4-8 eggs and the process begins again.

Above – this is how the red mite feeds, it has a proboscis, which has an anti-coagulant enzyme to allow the mite to extract blood from the host.

So once it is understood that the mite will do very well in a free range unit, we have the responsibility of understanding how many red mite we have, where they are and then understanding how many red mite it takes t have a negative performance on flock health and production. Then our treatments should take place once a fresh hold has been crossed. The danger of simply “eye balling” is that it is very easy to have confirmation bias, to not know where the hotspots are or to simply be too busy to inspect for them. That’s where trapping has been an important tool and it part of our services as we found that it allowed us to refine the use of either spraying Dergall or Exzolt treatment timing.

Above: an adult red mite surrounded by eggs

What is a Red Mite Trap?

It is a plastic tube that is about 6 cm long which has a corrugated carboard centre. It works on the principle of being placed in a position near to a red mite route. It takes 3 hours for a red mite colony to fully disperse after dark to feed. Once they have fed, they need a place to copulate, and lay eggs, which is out of lights and in “safe” area.

Two life stages, post hatching, the white mite are the first life stage, the larvae, which does not take a blood feed. The red mite is at life stage 3, the deutonymph. Which is only one stage away from adulthood and being fertile.

How Do They Work?

By placing the traps in area in which the birds cannot directly peck them (this leads to the birds pulling the cardboard, leaving you with a useless piece of plastic), an upright near to the front metal horizontal part of the system gives the most consistent and reflective result.

Where should I place them?

The standard 16,000 bird unit has two side and 4 sections. 1 red mite trap should be placed in a similar location as outlined above in every partition to understand where the populations may be heavier. The remaining 2 should be placed on the nest box walk ways on a metal upright near a horizontal cross member.

How long should they be in place?

5-7 days

Then what do I do next?

The red mite traps should be numbered and a note should be made of which number trap was placed into each section. The plastic tubes should be collected and placed into individual zip lock bags and frozen for 2 days. This will keel the red mite and prevent you moving them around the offices.

How do I monitor what I find?

Take a clean piece of white paper, wear gloves and remove the cardboard inner turn from the plastic sleeve, open this up and tap it out onto the paper.

The grading system for infestations is;

1-10 – light infestation, not significant on production or hen health at this point

10-40 – medium infestation, this will affect feather cover, aggression, egg production and disease transfer (notably E.coli)

Too numerous to count – an intervention is required urgently, as a heavy infestation on a modern hen will see raised mortality, reduced egg output and changes in behaviour.

The control of red mite is another article entirely, which we shall move onto later in the series. For help, advice, training and presentations, I can be contacted on Dave@rosehillpoultry.co.uk.