Dealing with the Little Fire Ant at Ramat Hanadiv: Mapping, Treatment and Monitoring

The little fire ant is a tiny, red ant, active day and night, which stings humans and their pets and displaces other arthropods. It causes severe harm to the ecosystem and constitutes a severe hazard to humans.

In 2018, the little fire ant reached Ramat Hanadiv and spread rapidly throughout the Memorial Gardens, impacting significantly on local arthropods. We responded by mapping its distribution, conducting an eradication programme, and monitoring the local arthropod community to assess its recovery.

Invasion by the little fire ant is a global problem. Our efforts to eradicate it must be part of a broader approach that includes informing professionals and the wider community.

The little fire ant (Wasmannia auropunctata) is one of the one hundred most harmful invasive species in the world. This is a generalist, omnivorous species with an ability to establish its nest in a range of habitats such as lawns, trees, houses, agricultural fields and natural landscapes. Established populations of the ant cause severe harm to ecosystems and constitute a serious hazard to humans. In Israel, the main source of dispersal is nurseries, from where the ant spreads mainly through plant pots, compost, soil and gardening equipment.

At Ramat Hanadiv, high population density of the little fire ant, which was observed in the Memorial Gardens in the summer of 2018, caused a serious hazard for visitors and gardening staff and concerns regarding ecological harm to populations of different animals. Monitoring by the gardening staff and research by Ramat Hanadiv, in collaboration with the Entomology Lab for Applied Ecology at Tel Aviv University (headed by Ittai Renan) in June 2018, showed that most of the garden area was infected.

Similarly, the abundance and richness of the other arthropods living in the gardens was significantly lower in areas highly infected by the fire ant compared to areas with low infection or no ants at all.

After examining different alternatives for dealing with the fire ant and its harmful impact, we decided to spray with pesticide. To examine the effectiveness of the pesticide and whether it causes undesirable harm to other arthropods in the gardens, we conducted a series of samplings at different periods of time – on the spraying date and during the months that followed. After two years and seven rounds of spraying, the fire ant population shrank significantly, but was not completely eradicated. In parallel, we monitored the recovery of the ground-dwelling arthropod community (using special traps) in the gardens, as well as the bees and the butterflies. We found that the pesticide did not cause any harm to the arthropod community.

Due to the broad distribution of the ant in the gardens and the complex nature of the landscape, and since there is no sufficiently effective pesticide in Israel, it seems that it will not be possible to completely eradicate the ant from Ramat Hanadiv. Therefore, it is important to continuously monitor the gardens, as well as the seedlings and gardening materials that come in from outside, and inform professionals and the wider community about this issue. In this way we will be able to keep the population under control, prevent extreme increases in nest density and prevent the spread of the ant into the natural areas surrounding the gardens.