Climate change, international trade and expanding transportation networks are accelerating the spread of invasive species, posing growing challenges for agriculture, biodiversity and public health in Türkiye.

Changing climatic conditions, expanding international trade and transportation networks, and increased human mobility are accelerating the spread of invasive insects both globally and in Türkiye. According to Prof. Dr. İzzet Akça of Ondokuz Mayıs University (OMU), nearly 60 invasive insect species are now known to have entered Türkiye at different times.

Prof. Dr. Akça, Head of the Division of Entomology in the Department of Plant Protection at OMU’s Faculty of Agriculture, explained that invasive species such as the brown marmorated stink bug, Asian tiger mosquito, citrus longhorned beetle, vampire moth and tomato leafminer have become increasingly common in different parts of Türkiye in recent years.

Their high reproductive capacity, ability to feed on a wide range of plants and adaptability to changing climatic conditions make these species particularly difficult to control. Invasive insects can pose risks not only to agricultural production but also to biodiversity and public health.

Not Every Insect Is an Invasive Species

Speaking to Anadolu Agency (AA), Prof. Dr. Akça stressed that not every insect encountered in large numbers in nature should be classified as invasive.

“For an insect to be considered invasive, it must first arrive in a region where it does not naturally occur. It must then become established, spread rapidly and cause economic or ecological damage,” Akça said. “Simply becoming abundant in a particular area or developing into a significant pest does not, by itself, make a species invasive.”

Around 1.2 million insect species have so far been scientifically identified worldwide, while the actual number is estimated to exceed five million. Akça emphasised that the vast majority of these species are not harmful.

“Only around 1–3 percent of insects in nature are harmful, while approximately 20–30 percent are beneficial,” he explained. “Most of the remainder perform important functions in the decomposition of organic matter, soil formation and the maintenance of ecosystems.”

Approximately 1,000–1,500 invasive insect species have been identified worldwide.

“Türkiye is home to around 25,000–30,000 insect species, while the number of invasive insect species identified as having entered the country at different times has approached 60,” Akça said.

Invasive Species Threaten Agriculture and Public Health

Among the invasive species currently causing the greatest economic concern in Türkiye are the brown marmorated stink bug, citrus longhorned beetle, Asian tiger mosquito, vampire moth and tomato leafminer (Tuta absoluta).

According to Akça, many of these species, particularly the brown marmorated stink bug, can cause substantial losses in both the yield and quality of fruit and vegetable crops.

The Asian tiger mosquito, however, poses a different type of concern due to its public health significance.

“Other invasive species are primarily agricultural pests, but the Asian tiger mosquito is a species that must also be considered separately from a public-health perspective,” Akça noted.

“Ticks Are Neither Invasive Insects nor Insects at All”

Akça also addressed a common misconception surrounding ticks, whose populations have attracted increased public attention.

“One issue frequently confused by the public concerns ticks. They are not invasive insects. In fact, they are not insects at all; they belong to the mite group,” Akça explained. “However, they are extremely important to human health because they can transmit Crimean-Congo haemorrhagic fever. Their populations have been observed to increase alongside climate change.”

Global Warming Is Not the Only Factor

Akça stressed that the spread of invasive species cannot be attributed solely to climate change. Global trade, logistics networks and human mobility also play major roles in carrying species into new environments.

At the same time, rising temperatures can allow species with high reproductive capacity to produce more generations.

“The brown marmorated stink bug can feed on more than 300 plant species. This means it can feed on almost any plant it encounters,” Akça said. “The citrus longhorned beetle can likewise survive on numerous fruit and ornamental plants. These characteristics make it easier for such species to adapt to new regions.”

“A brown marmorated stink bug can travel hundreds of kilometres even on the outside of a truck, rather than inside its cargo area,” Akça explained. “It can reach Adana on a vehicle departing from the Georgian border. This resilience plays an important role in their invasive success.”

The brown marmorated stink bug was first detected in Türkiye in 2017 and subsequently spread rapidly from the Black Sea Region towards the Marmara Region and inland areas.

No Single Method Is Sufficient for Effective Control

Prof. Dr. Akça emphasised that chemical spraying alone cannot provide an effective solution to invasive insects and that successful control requires a detailed understanding of each pest’s life cycle.

As part of biological control efforts against the brown marmorated stink bug, the samurai wasp, a natural enemy that has been successfully used against the pest in several countries, has also been released into the environment in different parts of Türkiye.

Akça cautioned, however, that releasing samurai wasps alone would not be sufficient. Biological control needs to be accompanied by appropriate chemical control measures, and managing established invasive species may require sustained efforts over a long period.

He also noted that residents can take protective measures using appropriate biocidal products, particularly during the overwintering period.

“This species does not directly sting or poison people, but because it can occur in large numbers inside homes, it can negatively affect quality of life,” Akça said. “For this reason, it represents a significant problem not only for agricultural production but also for everyday life.”