Expert: There will probably be no mosquito plague this year

A spring without significant rainfall and almost a decade of deepening hydrological drought means there are fewer mosquitoes. This year, there will probably be no mosquito plague - told PAP Prof. Stanisław Czachorowski from the University of Warmia and Mazury (UWM) in Olsztyn.

Although there were rainy days in May, according to preliminary data from the Institute of Meteorology and Water Management, rainfall this month in most voivodeships was lower than the average for the years 1991-2020.

Prof. Czachorowski assessed in an interview with PAP that "there will probably be no mosquito plague this year". "We would be in danger if we had a lot of water after heavy summer rains. Mosquitoes always appear locally, like other insects, but there are not many of them. We have a relatively dry spring and almost a decade of deepening hydrological drought. Hence, many such spring habitats have disappeared and there are fewer mosquitoes, as well as other aquatic insects," he noted.

The scientist emphasized that mosquitoes have the best conditions for breeding when there is a lot of shallow, seasonal water in the environment. He explained that these are, for example, puddles, places where a river floods, and small water bodies where there are no fish.

"Mosquitoes are excellent colonizers and quickly settle, whether they lay eggs in small water tanks, sometimes in barrels, or somewhere under a roof," he emphasized.

According to the expert, a sudden increase in the mosquito population is unlikely. He emphasized that individual heavy rains or larger July rainfalls could cause more water to be available locally, and mosquitoes - as good colonizers - could quickly rebuild their population. He added, however, that the puddles would have to persist for at least 2-3 weeks, but the effect would be local.

In Czachorowski's opinion, the best method that local authorities can use to limit the mosquito population is natural methods. "I think that the most effective method is their natural enemies - swifts, bats, swallows, insectivorous species in general, but also predatory insects such as hornets, dragonflies, etc. Modern construction deprives these bird species of nesting places, which is why their population is decreasing. Local authorities should create new places for them by erecting nesting boxes," he noted.

The expert noted that vegetation can also help reduce the number of mosquitoes. He explained that some plant species can repel and disorient insects with their scent.

"There are also chemical methods, but they cause more harm than good. In extreme conditions, of course, there are possibilities of chemical mosquito control, but we should rather take care of the balance in nature," he said. "In tropical countries, where the dengue or zika virus threatens, attempts are made to limit the number of mosquitoes through genetic modifications and releasing sterile males into the environment. In our conditions, I think that it is a matter of appropriate selection of herbaceous plants and trees in places that we care about the most," he added.

The professor also noted that with global warming we can expect migration of southern mosquito species. He admitted, however, that there is no reason to worry at present, as it has no sanitary significance.

According to Czachorowski, during the period when mosquitoes are most numerous, it is important to choose the right time of day to leave the house. He explained that mosquitoes do not like dry air and sun. If possible, it is also worth wearing a long-sleeved shirt for a walk. The professor noted that using repellents, i.e. mosquito preparations, which can be purchased in pharmacies, will be effective. When going to the plot, you can also buy special scented candles that repel mosquitoes .

Local authorities in Polish cities use various methods to combat mosquitoes. In Warsaw, the city office is not planning any mosquito control campaigns this year - informed Magdalena Młochowska, the coordinating director for green Warsaw, in May's response to an interpellation by city councillor Karolina Zioło-Pużuk. She emphasised that such actions can be taken by individual districts. Moreover - as she pointed out - spraying with chemical preparations has a toxic effect on bees, other insects and aquatic organisms. "Such campaigns also raise a lot of controversy due to the possible adverse effect on people, mainly allergy sufferers and small children" - she said.

In Wrocław, actions to limit mosquito populations depend on the prevailing hydrological and atmospheric conditions in a given year. The commune has been implementing a mosquito population control program since 1998 - informed the deputy mayor of the city Renata Granowska in May's response to an interpellation by city councilor Izabela Duchnowska. She added that decisions are made based on the findings of the "team for monitoring the dynamics of the development of the mosquito population". "As a result of many years of activities and observations, permanent, potential places of mosquito breeding have been designated, which have a significant impact on the increased nuisance of these insects for the city (approx. 300 permanent points)" - she emphasized.

Wrocław uses biological methods to combat the mosquito problem, such as using natural enemies of mosquitoes (predators, parasites, pathogens and bacterial toxins) to eliminate larvae in water reservoirs. The city also eliminates places where mosquitoes breed - for example, by maintaining the permeability of the drainage infrastructure. "Chemical treatments are performed only in situations of increased nuisance from adult mosquitoes," noted Vice President Granowska.

In Lublin, mosquito control has been carried out for about 20 years, but this practice was discontinued last year. Anna Czerwonka from the Lublin city hall told PAP that the city is taking other, ecological actions to combat mosquitoes. "In recreational areas, plant species that repel these insects are selected. In addition, nesting boxes for swifts and bats, which are natural enemies of mosquitoes, are installed," she said. She added that in early spring, the city conducts amphibian protection actions, which also help in the fight against these insects. (PAP)

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