During one of the regular inspections of the foliage at the wetland sanctuary and heritage (organic) garden by Nature Seychelles’ staff, it was discovered that the site had an infestation of the ‘hairy caterpillars’.
There have been various reports of infestations on several islands in Seychelles of the yet to be identified caterpillars. Some schools had to be closed down for fumigation as the caterpillars cause painful rashes when their hairs come into contact with the skin.
The Division of Risk and Disaster Management (DRDM) is now spearheading a strategy to combat the caterpillar infestation. They will be working in collaboration with the National Plant Protection Office (NPPO), the Plant and Animal Health Services (PAHS) and the Seychelles Agricultural Agency (SAA); a welcome piece of news, as several methods of eradicating the caterpillars continue to be applied at The Sanctuary.
The skin immediately becomes irritated and a rash appears on contact with the caterpillar hairs
On receiving the information that the caterpillars had been spotted at The Sanctuary, Robin Hanson, Nature Seychelles’ Green Health Manager set out to identify the trees with the caterpillars. This was two weeks ago.
“There were four trees in a localised area within our site that had caterpillars,” Robin explains. “There is also one tree beside our premises that also had quite a few caterpillars on it.” He then went on to contact the department of environment and a private pest control business for information on handling the pest.
Robin then bought a bottle of Nilinsect, an organic and therefore environmentally friendly insecticide from the Union Vale agricultural store. It was advised that the spray should be applied after five in the afternoon as the strong daylight rays could reduce its potency. The spray should also only be applied every 12-15 days.
The sticking agent in the insecticide is important in preventing allergy after the caterpillar is dead
Rather than just killing the insects the spray has a sticky agent that binds the allergy causing hairs. The spray also killed and other pests that were in the nearby garden area as it is effective on a multitude of insects. However, it was noticed that only the smaller caterpillars had been killed while the more mature ones and the eggs were not greatly affected by the spray.
“I then decided to go and buy a kerosene torch and extra wick so that we could use the flame to kill the eggs and mature caterpillars,” Robin explains. By hovering the flame lightly over the leaves, careful not to start a fire, it was then possible to clear more of the larger caterpillars while singeing their hairs.
Several higher branches were also pruned and these allowed to fall into the wetland. Although this was great in terms of providing more nutrients into the water and creating new micro-habitats under the water, it was discovered that the caterpillars were not completely dealt with as the caterpillars and their hairs do not break the surface tension but rather float in the water.
Using a flame to singe the hairy caterpillars
The infestation has so far reduced greatly especially after the second application, which would have eliminated any newly hatched caterpillars . The challenge remains not being able to control new infestations from neighbouring sites. For instance, it is uncertain whether and how much of an infestation there is in the adjacent tree covered private property.
During this time, Nature Seychelles staff and visitor movements were limited to certain areas of the Heritage(organic) Garden and The Sanctuary to avoid any contact with the caterpillars. Additionally, staff working on spraying, singeing and pruning wore protective gear while working. The only allergic reaction to the hairy caterpillars at The Sanctuary so far was experienced by Robin.
“I did not wear protective clothing against the caterpillar when I got into the water to cut a branch,” he says. “I was only wearing the waders unaware that the hairs were still in the water.”