About the Insect Suppression Programme

The programme aimed at killing mosquitoes is causing environmental disaster!

About the Insect Suppression Programme Fogging vehicle on Hvar, 2022

Every year, the County Institutes of Public Health (ZZJZ) issue two documents that describe in detail the rules governing the national pest control programme: "Programme of mandatory preventive measures for disinfection, insect suppression and rodent control" and "Implementation plan for mandatory insect suppression and rodent control". For each region, these documents remain largely the same, with minor changes, from year to year. Local authorities pay for these documents and the supervision of the Institute. On Hvar, four sets of these documents are issued annually, although the information for each local administrative district is essentially the same, with minor variations.

In practice, the rules specified in those two documents are not fully respected.

Why suppress insects?

The goal of the programme is to eliminate mosquitoes, or at least control their numbers, to prevent the risk of mosquito-borne diseases such as dengue fever and West Nile fever.

Are mosquito-borne diseases a significant problem in Croatia?

Despite the growing number of mosquitoes reported most years, the diseases that they can transmit have not caused major health problems in Croatia to date, unlike circulatory problems and cancers. Many of the reported mosquito-borne diseases are imported. The figures vary greatly from year to year. There is no evidence that an insect control programme affects disease incidence. In fact, the programme is known to be unsatisfactory. "The results of adulticidal procedures are temporary, so they are carried out when the mosquito population is at such a level that it is not acceptable to the population." (Programme of mandatory preventive disinfection, insect suppression and rodent control measures in the Jelsa Municipality, 2023, p.7.)

It seems that in some cases action is taken just to appease people who complain about being bothered by mosquitoes!

Insecticides cause more problems than they solve.

Nowadays, insecticides are the main weapon for controlling insects under the Insect Suppression Programme. Extensive insecticide spraying against adult mosquitoes is carried out several times a year, either from fogging vehicles, or in some areas from the air. There are also larvicidal actions, for example using the insecticide Bacillus Thuringiensis israelensis and/or growth inhibitors (IGR) such as diflubenzuron (Programme of mandatory preventive disinfection, insect suppression and rodent control measures in the Jelsa Municipality, 2023, p.5.). All the insecticides used harm bees and other pollinators and carry potential risks for human health and the environment. Some of the insecticides used so far have subsequently been banned as 'plant protection products' in the European Union, some of the products in current use are not approved, while some, such as cypermethrin-based products, should not be used outdoors during the flowering of wild or cultivated plants.

Warnings about fogging operations are inadequate

"The public should be informed in advance about the planned implementation, the type of biocidal preparation that will be used, the time and possible risks for certain categories of sensitive or sick residents, and beekeepers should also be informed about this in order to take timely protection measures for bees." (Programme of mandatory preventive disinfection, insect suppression and rodent control measures in the Jelsa Municipality, 2023, p.7.)

Over the years, warnings of upcoming fogging operations using chemical pesticides have become fewer and fewer. Sometimes they appear only a day or a few hours before the action, for example around the City of Solin, with a warning published on the City's portal on 06/19/2023, action 02:00 06/20/2023; in Split, there was a warning on 25.07.2023. 21:08 in the regional newspaper Slobodna Damlacija, for the action at 02:00 the same night (July 26th, 2023) with no notice given on the City of Split portal. Sometimes there is no warning at all, for instance for the fogging operations in Jelsa and Stari Grad, which took place on July 18th and 19th 2023.

Details of the insecticides to be used are almost never included in the warnings, although under European law citizens have a right to know what chemicals they may be exposed to.

Dangers are inherent in any poison dispersal programme. The lack of adequate warnings creates unacceptable additional risks to people and the environment. The only realistic way to inform the public about the planned fogging actions is to notify all citizens by mail or e-mail, in the same way as local bills are sent.

Insect suppression using pesticides is ineffective and even dangerous

"The tiger mosquito was first recorded in the Split-Dalmatian County in 2005, and today it dominates as the most important public health mosquito species in addition to the common mosquito... So far, it has been shown that the preventive measures and larvicidal actions have not succeeded in preventing the development of adult mosquitoes to the extent that they do not represent a public [? sic - ?hazard]...The actions achieve a limited and temporary reduction in the number of mosquitoes because they do not directly suppress mosquitoes in the nests." (Programme of mandatory preventive disinfection, insect suppression and rodent control measures in the Jelsa Municipality, 2023, 3.1.4. p. 5)

"Adulticidal procedures are non-selective, so they can pose a danger to non-target species of nocturnal insects, and for their predators in the area of adulticidal procedures. Adulticidal practices can harm the health of vulnerable groups of people and the environment, including aquatic and terrestrial animals." (Programme of mandatory preventive disinfection, insect suppression and rodent control measures in the Jelsa Municipality, 2023, p.7.)

"According to Article 14, paragraph 5 of the Ordinance on the method of implementation of mandatory disinfection, disinsection and pest control, the application of biocidal preparations by hot or cold fogging from aircraft is prohibited over populated areas, national parks and other protected areas." (Programme of mandatory preventive disinfection, insect suppression and rodent control measures in the Jelsa Municipality, 2023, p.8.)

Although insecticide spraying is known to be ineffective, it is still promoted as 'necessary to control mosquito populations'. According to the rules, aerial spraying should only be done in exceptional circumstances, but it seems to be happening more frequently in recent years. The collateral damage from the use of pesticides is huge, biodiversity is decreasing every year. The relentless use of pesticides is undoubtedly a factor in reducing the number of natural predators of mosquitoes. The practice is counter-productive.

Precautionary measures

"Adulticidal actions against tiger and common mosquitoes will be carried out in settlements, so there should be no overlap with areas where bees live. If there are such areas, in agreement with the beekeepers, the bee pasture area will be bypassed (at a distance of at least 300 m) or the bees will be protected in some other way. In the case of adulticidal treatment of mosquito infestations in yards and around houses, residents drying laundry outdoors will be warned not to when the action takes place. Spraying of fruit and vegetable gardens will be avoided if the half-life of the inseciicide is inappropriate or the crops are sensitive." (Implementation plan for mandatory insect suppression and rodent control in the Jelsa Municipality 2023, page 3, page 8) . In practice, there are no such warnings on Hvar, and fruit and vegetable gardens, vineyards and olive groves are sprayed without exception in the fogging operations.

Preventive measures: education

According to the Programme and Plan, education of the population is an important part of controlling the number of mosquitoes, for example: "Suppression of mosquitoes is carried out every year during the summer season of mosquito activity through educational, larvicidal and adulticidal (systematic with a vehicle) actions." (Programme of mandatory preventive disinfection, insect suppression and rodent control measures in the Jelsa Municipality, 2023, II. p. 2)

"The Health Institute and the company implementing the measures distribute leaflets and will continue to do so, also advising citizens on how to combat mosquito breeding. For this purpose, an answering machine is available, offering advice on mosquito control, on the number 0800 300 100." (Programme of mandatory preventive disinfection, insect suppression and rodent control measures in the Jelsa Municipality, 2023, p.5.)

"Health education of the local population is carried out through leaflets, posters, informing the population through local stations, local newspapers and an active educational telephone / answering machine 0800 300 100, which is used to educate citizens and to collect information about mosquito infestations."

"The application of chemical mosquito control measures on public areas alone will not achieve a satisfactory effect. It is necessary to involve citizens in controlling mosquitoes. Preventive actions around the house (removing potential mosquito breeding areas) can significantly reduce the population of this species. A copy of the educational leaflet is attached to the programme, which the implementing company or the local authority can duplicate and distribute to the population during the implementation of insect suppression and pest control measures." (Implementation plan for mandatory insect suppression and rodent control in the Jelsa Municipality in 2023, 2.2, p. 4)

In practice, at least on Hvar, there has been no public education for years. The telephone number 0800 300 100 is no longer in use in 2023. The new number 021 401 103 emits only a fax signal.

Monitoring, preparations for insect suppression actions

"The adulticidal method, i.e. the suppression of flying insects, is the method of choice and depends on the expert judgment of the epidemiological service of the competent public health institute as a supplement to the larvicidal procedures, and is carried out using cold or hot fogging on the ground, for the treatment of smaller or larger target areas .”

"It is necessary to ensure the implementation of preliminary actions if and when a decision is made to implement adulticide procedures. It is necessary to determine the area to be covered with a plan of action, to determine the time of the aerosol application and to determine the required amount of insecticide (The procedural form for adulticidal insect suppression is attached to this document)."

"Based on monitoring mosquito activity over many years, the eventual number of adulticide procedures is planned if the number of mosquitoes has increased." (Programme of mandatory preventive disinfection, insect suppression and rodent control measures in the Jelsa Municipality, 2023, p.7.)

"Chemical measures to suppress adult forms of mosquitoes are planned to be implemented in the period from July to September if mosquito activity has increased." (Implementation plan for mandatory insect suppression and rodent control in the Jelsa Municipality in 2023, 2.2.2, p. 6)

"If mosquito infestations are identified, the Teaching Institute for Public Health will enter the locations into their database and update it electronically. Data for updating the database are obtained through field surveys, reports from citizens and the contractors' records." (Implementation plan for mandatory insect suppression and rodent control in the Jelsa Municipality in 2023, 2.2, p. 4)

"The scope: in each action, the contractor will aim to cover roadside areas with treatment from vehicles (83 km according to the contractor's report), but only in residential areas where the number of mosquitoes has increased." (Implementation plan for mandatory insect suppression and rodent control in the Jelsa Municipality in 2023, p.6.)

In principle, monitoring is the basis for action, but in practice it is not carried out in the Jelsa Municipality.


Following the insect suppression actions, the Teaching Institute for Public Health for the Split-Dalmatian County issues a report every year. It does not include a description or analysis, as promised in their contract with the local authorities, but only an 'opinion': "Measures of mandatory preventive pest control, larvicidal mosquito actions, adulticidal mosquito suppression in the Jelsa Municipality .. were carried out in accordance with the essential provisions of the "Programme and Implementation Plan of mandatory preventive rodent control and insect suppression.."

So are some of the Institute's instructions irrelevant? Is it irrelevant that fogging actions are undertaken routinely without special planning based on monitoring, without warning and without proper supervision? There is apparently no real oversight of how the insect control programme is implemented in practice.


It is clear that the insect control programme is not doing any good. It cannot achieve the desired goals. The programme is unworkable, dangerous and counter-productive. The instructions and recommendations of the Institute for Public Health are not respected. Long-term observation in the field shows that the programme, along with the excessive use of pesticides in agriculture, is certainly a major factor in reducing the biodiversity of the Island of Hvar and elsewhere in Croatia. The time has come for a more rational approach. Health education of the local population must play a key role, not only in preventing the spread of mosquitoes through natural methods, but also in teaching people how to protect themselves from mosquito bites.

© Vivian Grisogono MA(Oxon), July 2023


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