Ministry gives tips on how to cope with black fungus gnat |27 December 2016

Following numerous complaints from both locals and visitors, the Ministry of Health has given some tips on how to cope with those little flying insects which have been a nuisance especially at night in the homes and other establishments.

Some advice for control of these insects – known as black fungus gnats – and its effects are:

• Survey around the premises for potential breeding sites (decayed vegetation) and eliminate them;

• Use stronger white lights outside as they are attracted to light and get killed by it;

• Turn the lights outside on early, before sunset so that they get attracted and limit the numbers that enter the residences;

• Reduce lighting inside the house;

• Place a container of water under the lights;

• Close doors and windows early before switching lights on;

• Hang sticky tapes under lights;

• Use candle lights around dinner time;

• Install electric insectocutor (zapper) in most appropriate place(s);

• Avoid using insecticide sprays as swarming occurs around dinner time and chemical contamination of food may occur;

• If any gnats fly into your eyes, do not rub them. Instead wash your eyes immediately with clean tap or bottled water;

• If the eyes become red, itchy and or painful, contact your nearest health facility for advice;

• If you develop any skin itchiness, wash area with lots of tap water. You only need to consult a doctor if the swelling is extensive or severe.

Background:

The black fungus gnats are real nuisances. In Seychelles, they first appeared in large numbers in 2015 following long spells of rain. It appears that their breeding grounds are many and widespread. With the recent rain there seems to be a resurgence countrywide.

These black fungus gnats are also known as sciarid flies; they are small, dark, two-winged insects; they love compost, dung, rotting vegetation – in fact anything where there’s a rich source of nitrogen for them to feed on. There are thousands of species of sciarids throughout the world and they have been found in many European, South American, Asian and African countries where there has been periodic explosion of the population.

In nature, they play an important part in the breakdown of dead and decaying matter alongside the various fungi that are also involved with this process. In a natural habitat, this attribute makes them a useful part of the decomposition cycle but where protected crops are grown, the species that have adapted to these conditions have become a real pest.

A gravid female although only a few millimetres long – can lay up to 200 eggs. She chooses a suitable site for them such as moist, warm compost and after two or three days the eggs develop into larvae. These are easily recognised by their black heads on a thin white body. At first, they are tiny – only one or two millimetres long. As larvae, they feed voraciously on protein within the organic matter and they browse on fungi. After several stages of development lasting 3 to 4 weeks they pupate and a few days later emerge as adult flies ready to go forth and repeat the whole cycle.

The increase in fly numbers can be astronomical.

Black fungus gnat in Seychelles

Prior to 2015, there had not been any report of these insects. They suddenly appeared in many regions of Mahé, Praslin and La Digue, almost all at the same time. This indicates that they had probably been in the environment for some time and has had chance to propagate and extend their boundaries. Certain reasons have been postulated as to their origin. Most people believe that they have been introduced from outside but there are also schools of thoughts that say that they have been in our environment for many years. With climate change, that has brought about unusual amount of rainfall, temperature and humidity change and the availability of dead organic materials, conditions are favourable for their breeding, multiplication and population explosion.

This is what has been happening in the last few days in Seychelles. Complaints of the nuisances that they cause have been numerous, from locals as well as tourists.

While being a nuisance, these fungus gnats do not bite or cause any serious illness. However there have been reports of people developing eye irritation after direct contact of the gnats to their eyes. Rubbing of the eyes, especially with unclean hands can provoke conjunctivitis. There has been an increase in number of patients who have reported to the health centres with conjunctivitis in the last week but this cannot be conclusively linked to the fungus gnat. Some people have complained of developing itchiness on the skin or a mild rash after coming into contact with the gnats but this has been mild.

This fungus gnat population explosion will probably last from a few days up to a couple of weeks depending on environmental conditions and resurgence is also likely to happen, again depending on environmental and weather conditions.