Stanislav Viter
In recent weeks, a number of media reports have focused on a massive locust invasion in southern Ukraine. Some media outlets and officials have even referred to these locusts as “Egyptian”, complete with Old Testament analogies, while others claim the destruction of the Kakhovka Reservoir has played a role in the invasion. What kind of locusts are currently attacking southern Ukraine, where did they come from and how likely are they to spread?
A mass breeding and onset of migratory locust migration was observed in southern Ukraine in 2025, the consequences of a complex set of climatic factors, soil conditions, and vegetation development, as well as, of course, the war in Ukraine. Active hostilities, temporarily occupied territories, and damaged landscapes present significant challenges when it comes to studying the issue and planning and implementing prevention and mitigation strategies.
Most of the locust outbreaks in southern Ukraine in 2025 concern only one species of insect, the migratory locust (Locusta migratoria). Despite statements by some officials, these locust swarms have nothing to do with Egypt and the Egyptian locust (Anacridium aegyptium). The Egyptian locust is known to cause damage to croplands in the Caucasus, North Africa and the Middle East, but does not form swarms or migrate long distances.
The largest locust in Europe and the world’s most common, the migratory locust is found in steppe, semi-desert, desert and even tropical regions in Asia, where it gravitates toward large reed beds, especially in wetland areas in arid steppes and deserts. The largest foci of migratory locust distribution are the lakes and rivers of Kazakhstan and southern Siberia, and river valleys in Central and West Asia. Further south, locusts are found in large concentrations in the lower reaches of the Tigris and Euphrates rivers, near Lake Tuz in Turkey and in the Helmand River delta in the Sistan Basin (on the border between Afghanistan and Iran).
In Europe, migratory locusts typically inhabit southern regions, where they are found in their greatest numbers in the river deltas that drain into the Black and Mediterranean seas and, to a lesser extent, in forest belt wetlands and sandy areas bordering woodlands. Large reed bed areas of southern Europe and arid regions in Asia are most susceptible to locust migration.
Beyond Eurasia, the migratory locust’s range encompasses all of Africa, Australia and even New Zealand. In these regions, locusts also concentrate in relatively small areas of reed beds near large lakes (such as Lake Chad) and river deltas (including the Nile, Indus, Irrawaddy, Mekong, Ganges, and Zambezi rivers, the inland deltas of the Chari and Okavango rivers, and the Sudd wetlands in South Sudan).
Ukraine is located between two “locust worlds”: a forest zone with small, scattered populations and arid regions with large concentrations. In Ukraine, compact nesting foci of migratory populations also form, concentrated in the deltas of the Danube and Dnipro rivers, in the Sivash lake system, and to a lesser extent in the Dniester estuary and other estuaries along the Black and Azov coastlines. Locust populations are also found in large areas of steppe reed wetlands far from the sea, such as the Liman lake system in Kharkiv region.
Usually, even in large reed beds in arid regions of Africa, Asia and southern Europe, migratory locust abundance is low. But in years when mass reproduction occurs, it is in these areas that locust invasions take place.
What causes locusts to reproduce en masse?
To become capable of reproduction, locusts need a large amount of succulent plant matter. While reed/bulrush (various species of the genus Phragmites, primarily Ph. australis) are usually preferred, they can also eat cultivated plants (millet and corn). A single locust consumes vegetation equivalent to 1–1.5 times its weight every day, i.e. 3–4.5 grams/day. Reed beds provide excellent feeding grounds, and in arid landscapes, where natural vegetation tends to become scorched by late spring, they are almost the only place where locusts can mature and acquire reproductive capabilities. This increases the concentration of insects in these areas in hot, dry years.
The availability of sites to incubate larvae and lay eggs is another condition affecting reproduction. The locust lays its eggs in soil, in a clutch covered with a film that forms a kind of cocoon, where they mature for 15–30 days, depending on temperature conditions and soil moisture. Moist soil is essential for the development of eggs, because during incubation the eggs absorb an amount of water from the surrounding environment approximately equal to the total volume of the clutch itself. The soil should be of light composition, ideally loess, or sandy loam. Migratory locust eggs also need high temperatures, so a balance between moisture and warmth is necessary.
These specific conditions may arise when hot weather is combined with frequent but brief rains, typical for the wet season in arid savannas and tropical semi-deserts. Another habitat option is irrigation systems, where in dry months soil is artificially moistened and excess irrigation water can drain off into desert areas near reeds. In arid regions of Asia and North Africa, it is irrigation systems that unintentionally create these conditions and artificially stimulate locust reproduction.
When a proliferation turns into an invasion
Returning to the climatic conditions described above, first drought and heat drive locusts into reed beds—the site of future reproduction. If the favorable conditions described above occur, locusts not only have an excellent food source in the form of succulent reeds, but also large areas of well-moistened soil. Since the places where eggs are laid and larvae develop (open areas of soil adjacent to reeds) and feeding places (reed beds) are separate, daily migrations are necessary. If clutches survive the winter and the soil is moist and well-warmed in summer months, large clusters of larvae form in these warmed areas.
In such large groups, larvae often come into direct physical contact with each other, prompting the secretion of pheromones that trigger larval development under the “gregarious phase” scenario. Such larvae need constant contact with other individuals, and staying in swarms becomes a necessity. They grow faster (by 20-30%) than solitary phase larvae, grow larger, more mobile, resistant to disease, and can tolerate prolonged starvation. Adult individuals in the gregarious phase lay fewer eggs per mating (up to 300, compared to 1200-1300 in the solitary phase). However, gregarious females mate more often, their eggs develop faster, and their offspring grow up to be more resilient.
Larvae and adults in solitary and gregarious phases differ in appearance, both morphologically and in coloration. Solitary individuals have a mostly green head and thorax and grayish, while their wings and abdomen are grayish and rather pale; their wings often have a greenish-olive coloration. The back of the gregarious form is flat or even slightly concave, but in the solitary phase it is curved in an arc, forming a peculiar keel.
Adult individuals in the solitary phase vary in length from 35 to 50 mm, while in a gregarious phase, their size ranges from 40 and 60 mm long.
Migratory locust, intermediate phase (September 2023). The image on the left shows a characteristic solitary phase individual – green head and thorax. The gregarious phase is characterized by the shape of the dorsal side of the thorax—a curved ridge. The coloration of the individual is closer to that of the gregarious phase. Source: Stanislav Viter
The concentration of locusts caused by climatic conditions is a signal to prepare for migration. Accumulation of locusts at a density of more than ten adults per kilometer of route is a warning that may indicate gradually increasing abundance. This is especially true if it is observed early in the season—in June and the first half of July. During mass reproduction, the population can reach dozens of individuals per square meter.
Overpopulation in larval clusters triggers migration regardless of the availability of food sources in a given area. During their larval stage (35–40 days), insects can travel more than 30 km on foot.
After six instars (development stages between molts), larvae eventually morph into adult winged insects. If they were gregarious as larvae, the adults continue to lead a nomadic lifestyle in large swarms. Now equipped with wings, these travelers of the insect world can be a true disaster for croplands. Winged adult insects can travel 30-100 and even 120 km per day. These swarms usually follow the wind or fly at a slight angle to it, traveling 200–300 km from their hatching sites. There have also been cases when swarms have traveled 1,000 and even 2,500 km! Not every wind is favorable however—when wind speeds reach 10 meters per second, migration stops for winged insects and walking larvae both.
Factors contributing to the 2025 locust invasion in southern Ukraine and in the future
Mass breeding and the onset of migratory locust migration was observed in southern Ukraine in 2025, a consequence of the types of climatic factors, soil conditions, and vegetation development described above. Details of the event’s causes and development include:
- Extreme flooding of egg-laying sites along the lower Dnipro River followed the destruction of the Kakhovka Dam in 2023. Receding floodwaters exposed large moist areas, optimal spots for egg laying and feeding (wetland reed beds, saturated with flood waters, especially in Lower Dnipro National Park and the Kardashinsky wetlands). The exposed basin of the Kakhovka Reservoir also provided similarly optimal conditions, namely open areas of moist and sun-warmed substrate and large areas of forage plants.
- Large new areas of suitable habitat appeared alongside the insect’s natural habitat in reedbeds in the Dnipro River delta.
- Meteorological factors including a very warm winter with minimal freezing of soils in 2024-25 favored overwintering egg clutches. That warm winter was also preceded by a hot summer in 2024, with heavy rainfall from May to mid-July, followed by drought in August–September. That very warm and dry autumn contributed to the successful reproduction and survival of adult migratory locusts. There was also a significant increase in solar activity (an 11-year solar cycle peak coincided with a 100-year maximum in 2024 and 2025). History confirms that mass locust reproduction occurs precisely during periods of peak of solar activity.
- Woody vegetation overgrowth on the Kakhovka Reservoir bed in 2024-2025 will shrink locust habitat, a possible trigger for swarm migrations.
- Humans failed to respond to the arrival of migratory swarms, including, first and foremost, lethal measures to destroy swarms in cropfields flooded and abandoned because of the war as well as on the bed of the former Kakhovka Reservoir, measures which could have been implemented as early as 2023–2024. With ongoing military operations and lacking funding and available specialists, no monitoring of natural breeding sites is currently occurring. There are also new and existing breeding habitats located along the front lines, in temporarily occupied territories, and near combat zones. Waves of locusts are a long-standing pattern in countries experiencing conflict, a list which now includes Ukraine—where there is war, there are locusts. For example, military operations disrupted monitoring and prevented timely preventive measures against the spread of desert locusts in Yemen and during the 2022 Tigray war in Ethiopia.
- Airspace restrictions prevented treatment of mass reproduction and migratory swarm concentration areas. Military operations understandably make the use of agricultural aircraft impossible.
Further developments leave little room for optimism. Increased solar activity will continue for several more years, and the same applies to the El Niño phenomenon, with high temperatures and heavy rainfall in most regions of Ukraine. In addition, there are many suitable locations where new outbreaks may occur, namely reed beds in river valleys (very common in Ukraine’s steppe zone) and on the shores of lakes, sedimentation ponds, and reservoirs situated near croplands.
Widespread plowing of meadows and steppe areas right up to shorelines and reed beds is also a significant issue. In many cases, agricultural fields and reed beds are immediately adjacent to each other. These fields provide open areas of soil where larvae can incubate, forming large clusters, and where adult locusts can lay eggs. The predominance of crops that require more time to cover exposed soil, like sunflowers and corn, creates favorable conditions because the soil there holds more moisture than do completely exposed soils. Additionally, exposed soils warm more readily. In the case of cornfields, locusts actually experience them as analogous to reed beds thanks to the morphological and nutritional similarities of corn and reed plants.
In warmer months, wind systems over Ukraine enable locust swarms to fly north and, to a greater extent, east and northeast. But the changing climate causes sudden changes in wind direction, especially at low altitudes above the ground. This can cause swarms to stray significantly from their usual migration routes. And if the Danube Delta, the largest river delta in the region, is included, then locust invasions in such “favorable” years can cover all of Ukraine’s southern, central and eastern regions.
Some of the largest centers for the mass reproduction of migratory locusts—the deltas of the Kuban, Yeya, Don, Volga, Terek, and Kuma rivers—lie to the east of Ukraine. In recent years, numerous locust connections between these hotspots have been documented, particularly the constant migration of locusts from one hotspot to another. Essentially, several large foci have merged into a single chain for large-scale reproduction. Migrating from one focal point to another, locust swarms join together, creating super-swarms. Because they are found in different natural zones (steppe, semi-desert, desert) where the warm season begins at different times, migrating insects accumulate in the more northern and northeastern regions, joined there by local insects.
This article’s author assesses that if the meteorological trends of 2023–2025 continue, particularly dangerous locust swarms should be expected in the period 2026–2028.
Key infestation areas in Ukraine and prevention measures
Coastal estuaries and river deltas, large inland water bodies (lakes and reservoirs, especially the former Kakhovka Reservoir), and large river valleys are the most predictable areas for mass locust reproduction.
In southern and eastern Ukraine, mass reproduction outbreaks are most likely in agricultural landscapes outside of river valleys, and were observed in August-September 2023 in the Berestinsky district in Kharkiv region. These outbreaks did not re-occur in 2024.
What preventive measures are available today? Following are the simplest and cheapest measures that are also critically necessary:
- Creation of buffer zones at least 500 m wide around large areas of reed marshes. In such zones, tall grass meadow vegetation should be restored and bare soil areas should be prevented. It is particularly important that no cornfields are located in such buffer zones, they should preferably be sited at least two kilometers distant from wetlands).
- Strict adherence to crop rotation, and specifically not allowing corn to be grown on the same plot for more than two consecutive seasons.
- Chemical treatment should be carried out in areas where larvae incubate (if possible, followed by the removal of poisoned insects from the natural environment to prevent the poisoning of locust-loving predators). Preference should be given to targeted (anti-locust) chemical agents rather than broad-spectrum insecticides.
- Ban plowing on river floodplains! Habitat destruction often leads not to the disappearance of locust populations, but to their migration to croplands and the emergence of mass breeding grounds. Such development can have a particularly negative impact on agriculture in areas where mass reproduction of the white-winged grasshopper (Chorthippus albomarginatus) and the Italian locust (Calliptamus italicus) occur. Where plowing occurs, natural breeding grounds (meadows) will simply be replaced by artificial ones—croplands. This will result in even greater losses for agriculture.
- Promote the conservation and increased abundance of predators: starlings (Sturnus vulgaris, S. riseus), shrikes (Lanius sp.), small falcons (primarily kestrels Falco tinnunculus, F. naumanni), gulls (Larus sp.), rooks (Corvus frugilegus) and magpies (Pica pica), hooded crows (Corvus cornix) and common ravens (C. corax), bee-eaters (Merops apiaster), rollers (Coracias garrulus), steppe lizards (Saga pedo), steppe vipers (Vipera renardi), lizards (Lacerta viridis, L. agilis), and burrowing wasps (Podalonia sp., Sphex sp., Tachysphex sp.). This requires both the preservation of preferred habitats for these species and specific measures, including artificial bird boxes and nesting platforms for birds of prey. To increase the number of shrikes in agricultural landscapes, shrub areas measuring at least 2×3 m should be created at a distance of 100 m between groupings. Blackthorn bushes growing along forest edges where predators may also live should also be protected.
Comprehensive monitoring and research into the impact of landscape changes on locust populations must be implemented. For example, the changes occurring on abandoned land in combat zones and deoccupied territories as well as on fundamentally new types of agricultural land use in Ukraine require study. For example, rice fields, which, due to climate change, occupy increasingly large areas in southern Ukraine. Rice fields themselves, in totally transformed agricultural landscapes, are becoming pockets of biodiversity. However, there are no studies on how such radical landscape transformations affect locust populations in Ukraine’s climatic and landscape conditions.
Managing locusts in the context of climate, conflict and science
Under normal circumstances, migratory locusts are rare inhabitants of river floodplains and marshy lake shores. However, climate change and other human factors (lack of monitoring, wholesale plowing of natural meadows and steppes right to the edge of wetland areas, disrupted crop rotation, destruction of natural and artificial landscapes by war, etc.) create dangerously optimal conditions leading to migratory locust swarm outbreaks.
There are many species of locusts in both Ukraine and around the world. Only a few of them are capable of the kinds of massive population surges that residents of the Zaporizhzhia, Dnipropetrovsk, and Kherson regions witnessed this year. Some species of locusts are quite rare and even require conservation, while others are common inhabitants of meadows, forest glades, and steppe grasslands and balance the volume of plant matter in ecosystems.
It is important that such vegetation is removed, because otherwise it creates additional fuel reserves for fires in natural ecosystems. Fires release the carbon dioxide stored in plants back into the atmosphere, one of the most dangerous sources of greenhouse gases. Direct and indirect utilization of excess plant matter by locusts and excreted waste from the predators who feed on these insects improves carbon storage—it is reliably stored in organic compounds in the soil. In any case, carbon will not return to the atmosphere as quickly as it does when burned.
Mass reproduction of certain locust species in Ukraine—migratory locusts and, less commonly, Italian locusts—is the response of these insect populations to particularly favorable conditions that occasionally arise in arid ecosystems, places that are usually stingy with their “gifts” (steppes, semi-deserts and deserts, savannas, etc.). Human intervention in such ecosystems can cause locust populations to surge, and without precautionary and preventive measures (including landscape management and especially crop rotation compliance), these swarms can cause enormous damage to agriculture and negatively affect natural ecosystems.
Translated by Alastair Gill and Jennifer Castner
Main image: Migratory locust (Locusta migratoria migratoria) in gregarious phase. Kharkiv region, Berestinskii district, September 2023. Source: Stanislav Viter
