Disease Education & Prevention in Butterflies

Raising Healthy Butterflies
Reproduced with permission, from The Commercial Butterfly Breeders Manual
© Nigel Venters & Linda Rogers.


Captive Breeding

In captivity, natural predation is reversed, as you have removed the main causes of mortality by keeping your precious livestock predator-free! Therefore, other controlling checks come into play that are rarely needed by nature to control numbers. The vast majority of your losses will be through larval disease (bacterial, viral and fungal), protozoan infection in Monarchs, and pests killing the larval foodplant.


Bacterial, Viral, and Protozoan Infection

These issues are generally not a problem in nature. Wild stock always has disease present. This is rarely a problem with the following conditions: Healthy larva living low density, bright natural conditions, free airflow, plenty of healthy, growing foodplant!

Diseases, bacteria and viruses are always present in the wild population in very low concentrations. The adults roam over huge areas. The ova, larva and pupa are washed by rain, and blown by wind, resulting in pathogens being present in very low numbers. Epidemic proportions of pathogens are very rare. Problems arise with breeders when stock is kept indoors, with dense conditions, closed containers, damp food and inadequate airflow. It is a bit like meningitis, which is present in about 60% of human throats, but only a problem when certain optimum conditions arise. Given the right conditions, a virus can be induced from stock that was thought “clean.” Monarchs are quite healthy, carrying low doses of Ophryocystis Elecktroscirrha (Oe). There are probably traces of it everywhere at miniscule levels.

Now, you cannot emulate the outdoor conditions! But you can get as close as possible and learn to take steps that ensure disease is never a serious problem for you. I don’t propose to go into details here describing each of these infections as this can be found in many other books and manuals.

The names like “Bacillus Thuringiensis” and “Ophryocystis Elecktroscirrha” themselves are not helpful to you, as my advice to you would always be the same regardless of what causes the disease. Once your stock is afflicted, there is only one course of action and this manual is aimed at preventing it from occurring in the first place!

When the outbreak occurs, you will have to purge all of your stock, sterilise everything and start completely over! This is very tough to do when you’ve spent many hours looking after your precious stock but you just have to get on with it or it will just get worse and drag you down with it!

This manual’s focus is primarily prevention, and cure secondary. Following these procedures will spare the expensive loss of stock and time associated with cleansing your facility from ceiling to floor, discarding containers, destroying valuable livestock, purchasing replacement stock and losing money on lost orders.


Recognise Disease Infections

This may seem a bit daft as you would think recognising these infections is obvious, but many a newcomer to the business has been worried when they have seen the larva hunching up, not moving for a day or so and going through a heaving motion under it’s skin! This is just the larva changing it’s skin, and it is important you do not disturb the larva at this stage. Also, just before pupation the larva becomes restless and starts to wander about the cage looking for a suitable spot to pupate. The last dropping of a larva about to pupate is always undigested and sloppy do not worry if you see this happen. Only start to worry if you see:

  • Bacterial/Viral Infections (I call them “wilt”). The larva collapses into an empty bag and hangs from its claspers. This is the only disease I’ve once seen devastate larvae in the wild with the gregarious Nymphalid English “Peacock” larva (Inachisio, a similar species to the Mourning Cloak).
  • Diarrhoea. This can be caused by two reasons: one, because you have too much water in the foodplant (from standing in water too long) or two, by keeping the larva in too high humidity with no airflow. Damp food is acceptable if you have adequate airflow........ but deadly in closed plastic boxes!
  • Protozoan infection. This is sometimes called “green butt” by breeders! The symptoms are a shrinking larva with green-stained, bung-plugged anus.
  • Fungal infection. In this condition, white spores spread through filaments throughout the larva...see this and it means you are keeping the larva too damp with not enough airflow. This is exactly the same with ova, however if you spot this early enough it is the only infection you can deal with by introducing airflow.


Prevent Problem From Occurring

There are a few golden rules to follow that will minimise disease problems. You will always have a higher rate of disease-free stock if you use growing foodplant in an outdoor climate-controlled flight area (see Section 3.2). I do know that this is not always possible for everyone, especially when starting up on a small-scale with a few indoor cages to begin learning about raising butterflies. However, this is not the ideal way to raise butterflies, and is conducive to disease and infection in your stock.


So, let’s recap the causes. Disease is aggravated by:


  • Lack of cleanliness/sterilisation in cages, boxes, and equipment. Also, wash your hands before moving between cages.
  • Cages that are difficult to sterilise. Construct them out of aluminium or plastic (PVC), and avoid wood components.
  • Too-close contact between cages. If you have the space, keep stock apart from each other. If purging stock becomes necessary, you’ll lose less!
  • Poor air circulation.
  • Temperatures either too low or too high.
  • Dampness in closed plastic boxes.
  • Cramped conditions and lack of fresh foodplant.
  • Cut foodplant and (dare I say it?) ......artificial diet that you should only use if you are unable to get a fresh healthy supply of foodplant!
  • Failure to rotate stock between flight cages and different areas. (Sterilise and leave a cage or flight area “fallow” for a period of time.)


Cage and Enclosure Sterilisation

I never use a the same cage immediately after use, and give it a period which I call “lying fallow.” Depending on the pressure you are under, it is a good idea to follow this practice as it allows you to be a bit more harsh with your sterilisation procedures.

  • Grain Alcohol

    High-proof grain alcohol is effective and evaporates quickly. However, I always feel the need to drench a cage with the grain alcohol, as with rapid evaporation I’m not certain of complete sterilisation. This is a good method and the grain alcohol can be sprayed using a plant mister. Watch out for two things! Some plastics can dissolve in alcohol and also the stuff is very explosive. Watch out for fumes!

  • Bleach

    I used to use the bleach that the TV tells me “Kills 99%” of all known germs (I assume the 1% left are particularly virulent or the companies are just covering themselves against litigation should some germs survive!) This I mix up in water at 5% bleach, and zap around the cage until it’s soaked and then just leave it there to dry. Sometime later I hose the cage down two or three times before I dry it and use it again. Remember, if you have metal cages, sodium hypochlorite (the active agent in bleach) will eat into the metal if you use too strong a solution.

  • Baby Bottle Steriliser

    This is now my favourite sterilising solution. I use this undiluted when sterilising outdoor enclosures with growing plants. I put a plastic sheet down first as I tend to get carried away with the spray. I leave this to dry also, and then hose down once before use.

  • The Fallow Period

    I like to keep rotating usage of a few outdoor enclosures. This also allows for the “fallow” period which is a method of sterilisation.

Egg Sterilisation

Sterilisation of the ova is the best way to minimize diseases. Following are recipes I have used for sterilization of the eggs.

  • Equipment needed
    1 plastic tea strainer
    1 plastic pot (big enough to submerge contents of tea strainer)
    1 bottle of baby steriliser

Recipe 1:

Take a bottle of baby bottle steriliser and dilute to 0.25% solution. Place eggs in tea strainer and agitate in the solution by carefully shaking strainer from side to side. Leave submerged for 5 minutes. Rinse and dry eggs on paper towel. Place eggs in a container and breathe on them every day to keep them from drying out, until they hatch.

Recipe 2:

Get a bottle of Formaldehyde from the chemist. Check the strength as it will have already been diluted from 100% by the chemist. Further reduce the strength to 10%. Place the eggs in tea strainer and carefully agitate them in the solution by shaking the strainer from side to side. Leave eggs submerged for 40 minutes. Rinse and dry the eggs on a paper towel. Place the eggs in a container and breathe on them every day to keep them from drying out, until they hatch. (Do be careful with formalin as it is recognised as a carcinogen.)

You can try both for treatments for ultimate cleanliness, but NEVER allow the two liquids to mix during treatment or at any time, as this will produce lethal fumes!


International Butterfly Breeders Association, Inc.




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