BROMELIADS and MOSQUITOS

By: Rob Smythe M.Sc.

(Constantly updated version---Last update May. 2006)

Mossie details can be found at:

http://medent.usyd.edu.au/photos/mosquitoesofaustralia.htm

Taxonomy: I am not up to date with the science of mossie classification. The first name I give is probably the most frequently used while the one in brackets is probably the more scientifically up to date.

Fortunately broms and mosquitos donít come together very often.

Over 4 years I have monitored my broms for mosquito infestations.

Mosquitos that I have found in broms are :

1 Aedes notoscriptus (Ochlerotatus notoscriptus)---one of the salt marsh plague mosquitos. These blow in by the thousands from the salt marsh areas after rain and/or king tides. Those coming from our broms are negligible in number but do occur. The unfortunate thing about this mosquito is that it takes a trained eye to differentiate a well-fattened Aedes aegypti (the one councils are concerned with) from a partly starved Aedes notoscriptus. You need a lens to see the lyre markings on the thorax or the narrow white band near the middle of the proboscis. So rule one is all mosquitos with those football sock markings are not one of the very bad ones. Medically Aedes notoscriptus is of some concern as it can transmit Ross River Fever if you have infected kangaroos, possums or other carriers (not humans I believe) in the area. The presence of Aedes notoscriptus just in your garden and not a general infestation should be your main indicator that something could be wrong with your bromeliad hygiene. It has been suggested that it is a vector of dog heart worm. A . notoscriptus was found capable of carrying Murray Valley encephalitis using laboratory testing. If your neighbour asks if he will get Ross River Fever from your broms, ask him back if he has a possum in his roof. The possum is the bigger risk.

#2 Culex fatigans or Culex quinquefasciatus. I think these two names are synonyms This is an urban mosquito. A smallish light brown mossie with faint golden stripes across its lower body parts, hardly discernable to the naked eye. These breed in large numbers in my bird baths and every week they have to be tipped out taking care that they donít finish up in the broms. A research team from Tropical Health, looking for mosquito predators, found these mosquitoes in the side axil ponds in large vrieseas and alcantareas. I have since found them on two occasions in flowering Neoregelias. Health wise they are bad for the dogs as they carry heartworm. Interestingly in the bromeliads in my garden these wrigglers donít usually reach maturity as species #4 (below) usually eats them.

The other mosquitos listed below are low incidence and really the above two are your main concern in Townsville.

#3 The Orange? Mossie--Aedes tremulus ?Ė[I could have this wrong as I have only had one mossie to key out]- This is a very uncommon mosquito. The odd one is found around broms and also may indicate problems in the darker areas of broms like the wells in billbergias. If you see these, act by checking darkened areas. Name was given to me as a possibility by an expert as my one sample was not in that good a shape but it was collected from well water in a brom. I need to key out more, as A. tremulus does not appear orange enough in the photo that I have seen. I have collected ,in flight, orange mosquitos hanging around my broms. These key out as Coquillettida xanthogaster. Both the above should be considered innocent unless I can prove them guilty

#4. Toxorhynchites speciosus---a beautiful mosquito in more ways than one. It also has the football socks and is beautifully marked and is much larger than the others mosquitos mentioned. It stands apart, as it dances on the water in any of the plants with a sizable water pondage. You can bet that if you find a large pondage with wrigglers in it they are often quickly eaten and you finish up with only a very large solitary reddish wriggler. I have kept one of these wriggler alive for three months before I took pity on it and returned it to the vase. Growth depends on availability of food. I have fed wrigglers to one of them. The most I had available for food was seven at one time and these were all eaten in one night.

 

Mosquitoes present in Townsville but not found in Bromeliads (not by me anyway).

Aedes aegypti---After 4 years of close watching I have never found one wriggler of this species. I know from experimental work that they can live in the plants once introduced so be careful where you tip your dogs water or where you empty your bird bath.

Aedes vigilax--(Ochlerotatus vigilax) - Another of the salt marsh plague mosquitos A dark mosquito very strongly banded down the body. Another with foot ball socks markings. They arrive by the thousands after high tides if there has been a bit of fresh. If there has been a lot of rain we tend to see the other salt marsh mossie namely Aedes notoscriptus. Vigilax must need the salt, otherwise with the shear masses that arrive you would think they would breed opportunistically in broms, but they donít.

Mosquitos not found in Townsville that could be a problem in the future.

Aedes albopicta (Stegomyia albopicta) (Asian Tiger Mosquito)ódiscovered on Yorke Island in 2005. This is a cold tolerant species. It is a vector for dengue fever, encephalitis and yellow fever. This means two things. Firstly as Aedes aegypti is an urban tropical mossie while stegomyia albopicta is more rural so dengue fever could, if the mossie move south, move out of the cities. Secondly being more cold tolerant stegomyia albopicta could spread the disease right down to southern states. I have not been able to find out whether or not this mossie would breed in bromeliads.

I have read about the introduction of Aedes aegypti to this country and was lead to believe that it spread, following the caravan routs, right down to Adelaide then contracted back to the tropics. How interesting, could this be explained by the development of a tropical intolerant predator for this mossie? I canít think of any other explanation.

Keeping broms mosquito free.

You have the following options.

  1. Spraying with insecticide.
  2. Adding a hormone that stops wrigglers maturing.
  3. Washing out plants regularly
  4. Growing plants dry by piercing lower leaf area.
  5. Using predators to eat the mossie eggs and destroy wrigglers.
  6. Place water crystals to soak up water yet retain moisture
  7. Bacterial control.
  8. Natural control.
  9. Combination of the above.

In all cases keep detritus out of the plants and remove spent flowers. These supply food and serve as an attractant to mossies. They putrefy water which gives mossies the edge (surface breathers) over predators.

A few notes and opinions on these methods.

Spraying with Insecticide

  1. Do you really want to?
  2. Lots of birds including honey eaters drink from wells.
  3. Systemics kill bees, will they kill our honey eaters?
  4. It will kill predators.
  5. You will need someone to maintain program while on holidays.
  6. Going against usual rules use the same insecticide repeatedly. This gives resident predators a chance of developing immunity. Mossies fly in and should therefore not develop immunity.

Water Crystals

  1. Very good in shaded areas.
  2. Breaks down faster in hot areas.
  3. Good for holidays.
  4. Does not wash out in rain.

My observations

Non-toxic to wrigglers so they will survive if placed in wells with crystals.

Small wrigglers not inhibited. Larger wrigglers can get into trouble. Some get trapped and die but not all.

Broms filled with gel to near the surface wrigglers tend to die from overheating.

An experiment completed by me showed that not one ant would drink water where gel was present. Even low levels like 20% gel in the water are avoided completely by green ants. They drank only from the control flasks which had no gel.

An experiment to see if mossies breed in water with gel present is now completed. I have sterilized the water using the same samples that I previously had wrigglers in. Microwaved a couple of times to destroy wrigglers and possible predators. Three months on none of the gel containing containers developed mosquito larvae. Three control (no gel) flasks all developed mosquito larvae. I have a feeling that fresh gel does not work so well. I need to check this out.

Use of Hormones

  1. Can you tell a normal wriggler from an abnormal wriggler?
  2. Probably you need to apply the hormone whether needed or not.

What attracts mossies?

Water (Gel or dry growing can avoid this. Dry growing severely stunts plants. Only pierce matured leaves)

Heat

Carbon Dioxide (so no rotting material)

Pink colour (Donít let the water become tea coloured)

Washing out Plants

  1. At least weekly.
  2. When on holidays.
  3. OK for bush house grown plants.
  4. Difficult where leaf, fruits or flowers drop into the wells.
  5. Good idea to wash out wells and axil ponds on different days. This maintains predators.
  6. Difficult with a large number of plants.

Dry Growing

  1. Stunting, bleaching, burning will be more prevalent.
  2. Piercing needs to be done with large catchments. Can be disfiguring.
  3. Complex watering system required.
  4. Problems during wet weather.
  5. Fluting will occur.

Predators

  1. Predators are in low numbers at the start of the mossie season.
  2. Best ones you have to collect from a natural source.
  3. Need to apply them with a watering can at the start of the wet season.
  4. Need to apply them to new pups unless you have lots of frogs to spread them.
  5. Some fly in.
  6. Good to have a predator breeding in a pond in the garden.
  7. No rotting material in the broms.
  8. Remove spent flowers.
  9. Mesocyclopsóthe gun predator for Townsville. Discovered by Dr Brown in pondage in Townsville. I discovered it subsequently in Broms. After applying these predators to my broms I watched for three years and no nasty mossie infestations occurred. If you keep them in pondage in your garden, donít add mosquito fish or any other small fast moving fish as they eat our desirable predator. The predator co-exists with the slower moving fan tail gold fish.

http://cfb.unh.edu/CFBkey/html/Organisms/CCopepoda/OCyclopoida/GMesocyclops/mesocyclops_edax/mesocyclopsedax.html

j) I am testing out other possible predators found in broms .

Two good predators have appeared, mesocyclops of course and the other is awaiting identification to species. Both these are permanent residents in broms. Other organisms worked well but eventually flew away and then larvae appeared. The best I can do re identifying second permanent predator is that it is a minute crawling ostracod see http://152.2.81.1/parkproject/harp/Courses/Ostracod_page.html

These amazing little shrimps in pippin like shells can crawl up the inside walls of the glasses I used for my experiments. I assume they eat the rafts of mosquito eggs on the surface.

http://www.gre.ac.uk/schools/nri/earth/ostracod/introduction.htm

The second paper mentions that ostracods occurs in broms and that they are predaceous carnivors. As I went to great care to separate the various organisms I do not know if the predators found also eat each other.

Fly away predators: The various larval stages of midges I have previously reported can trap larger wrigglers. In my home lab tests these worked to prevent mossies but eventually flew away and were not replaced. In broms they seem to be always present if you donít wash them out and in the few observations that I made the midge with black larvae do successfully cohabit with them.

 

Bacterial Control

  1. Bacillus thuringiensis var. israelensis.
  2. Believed to be toxic only to insects.
  3. Availability to home gardeners ??
  4. Kills predators as well.
  5. Washes out.
  6. Breaks down in sunlight.
  7. Clay or organics in water interfere.
  8. Two formsólive or dead bacteria.

Natural

Research has shown that only a few species of mosquitos breed in some select species of broms in the wild. (none of those mossie species occur in Australia). That is where research stopped. My personal belief is that broms that normally grow in shade exude surfactants into the wells. Full sun plants donít appear to do this and control mossies by becoming hot. Grow these cool and I have observed problems. These are not much more than observations based on:

    1. vases which froth when I hose them have never had larvae.
    2. Putting bromeliad leaves in a blender has shown much frothing.

Worst infestations have occurred in the following genera. Worst first.

Alcantarea

Aechmea

Neoregelia

Vriesea (larger varieties)

Billbergia

Questions yet to be Answered:

Do our Ostracods have a swimming phase?

Can they catch and eat Mesocyclops?

Bromelianóthis is a protein hydrolizing enzyme found in pineapples. Insects found in other fruit are digested when they enter a pineapple. Could this chemical be sequestered into the well water of broms?

Surfactants: are these produced exogenously or endogenously in broms. My simple experiment with the blender suggests the latter.

With all that is stacking up against them it is a wonder that a mosquito is ever found in a bromeliad. If we could keep leaves and dead flowers and the like out of our plants and not wash out the wells we may never see one.


http://fcbs.org/