Pests

Biology

Aphids are small insects (1–2 mm) with soft, pear-shaped bodies. Color varies from yellow-green to dark green, almost black. During the warm season, they reproduce parthenogenetically — females give birth to live larvae without fertilization. A single female produces 8–22 larvae per day, which reach sexual maturity in just 3–4 days (Sharma, 2016). Up to 20 generations can occur per season. Aphid colonies settle on the underside of young leaves, on shoot tips, buds, and ovaries.

Signs and Damage

• Leaves curl downwards, become wrinkled, and turn yellow.
• Young shoots become deformed, and growth slows down.
• A sticky coating — honeydew — appears on leaves and fruits, excreted by aphids while feeding. This honeydew quickly becomes colonized by sooty mold, covering leaves with a black coating and impairing photosynthesis (Mondal, 2020).
• Under heavy infestation, plants appear stunted, and ovaries drop off.

The most dangerous aspect is that aphids are vectors of viruses: Cucumber mosaic virus (CMV), Watermelon mosaic virus (WMV), Zucchini yellow mosaic virus (ZYMV), and Papaya ringspot virus (PRSV). These viruses are incurable and can destroy the entire harvest.

Prevention

• Regularly inspect the undersides of leaves, especially in early summer.
• Remove weeds — they serve as aphid reservoirs (Mondal, 2020).
• Avoid over-fertilizing with nitrogen: excess nitrogen makes tissues more succulent and attractive to aphids (Karataev and Sovetkina, 1984).
• Plant repellent plants nearby: dill, fennel, mint, marigolds — they attract natural enemies of aphids.

Control Methods

Biological. Your main allies are ladybird beetles (Coccinellidae), lacewings (Chrysopidae), hoverflies (Syrphidae), and aphid parasitoid wasps (Aphidius spp.). A single ladybird beetle eats up to 50–100 aphids per day. To attract them, sow nectar-producing plants (buckwheat, dill, mustard) near your plantings (Pessarakli, 2016). The fungal preparation Beauveria bassiana is also effective — it infects aphids under conditions of high humidity.

Mechanical. For light infestations, aphids can be washed off with a strong jet of water — but do this in the morning so leaves dry before evening. Pruning heavily infested shoots also helps.

Chemical (last resort). If colonies are growing and beneficial insects cannot cope, use products based on natural pyrethrins, potassium soap, or plant oils. These are less toxic and degrade quickly. Among systemic insecticides permitted on cucurbits are products with the active ingredients acetamiprid or imidacloprid, but their use must strictly follow instructions and account for pre-harvest intervals (Kemble, 2022).

Biology

The mite is 0.3–0.5 mm in size, nearly invisible to the naked eye. Color varies from yellow-green to orange-red (overwintering females). The optimal temperature for development is above 27 °C, with the entire life cycle from egg to adult taking only 5–7 days (Pessarakli, 2016). A female lays up to 200 eggs. Dry weather, dust, and lack of rain contribute to explosive population growth. Mites live in colonies on the underside of leaves, covering them with fine webbing.

Signs and Damage

• Small light spots — puncture marks — appear on the upper leaf surface. With mass reproduction, leaves take on a mottled appearance, turn yellow, and dry out.
• Fine whitish webs are visible on the underside, with tiny dots moving within them.
• Leaves curl, plant growth is stunted, and fruits become smaller.
• Under severe infestation, plants may completely defoliate (Mondal, 2020).

The mite also secretes toxins that damage plant cells, compounding the damage.

Prevention

• Maintain air humidity: in dry weather, carry out overhead refreshing irrigation — this creates unfavorable conditions for the mite and promotes the development of fungal diseases that attack it (Mondal, 2020).
• Regularly water pathways and surrounding areas to reduce dustiness — dust promotes mite reproduction.
• Remove weeds and plant debris where mites survive unfavorable periods.
• Avoid overuse of pyrethroids: they destroy natural enemies of the mite and provoke outbreaks (Sharma, 2016).

Control Methods

Biological. Predatory mites — Phytoseiulus persimilis, Amblyseius californicus, Neoseiulus cucumeris — effectively suppress spider mite populations. In protected cultivation, they are released at a rate of 10–20 individuals per 1 m². In open ground, it is important to create conditions for their natural dispersal: avoid wide row spacing, leave areas with wild vegetation (Pessarakli, 2016). Preparations of Beauveria bassiana also help.

Mechanical. A strong spray from a hose dislodges mites from leaves. However, at high population densities, this method is ineffective.

Chemical (last resort). Use specialized acaricides — they act only on mites and are safe for insects. Products based on abamectin, bifenazate, etoxazole are indicated against spider mites on cucurbits (Kemble, 2022). It is important to alternate active ingredients to avoid resistance. Apply thoroughly, wetting the underside of leaves. A repeat application is usually required after 5–7 days to kill the new generation emerging from eggs.

Biology

Females lay eggs on the underside of young leaves. After hatching, larvae (nymphs) actively crawl (called "crawlers"), find a feeding site, then attach and become sedentary, feeding on sap. After 1–4 weeks (depending on temperature), they pupate, and adults emerge from the pupae. Up to 10 generations can develop per season.

Signs and Damage

• Adult whiteflies fly up in a cloud at the slightest touch to the plant.
• Eggs, larvae resembling translucent scales, and waxy secretions are visible on the underside of leaves.
• Leaves are covered with sticky honeydew, which hosts sooty mold, impairing photosynthesis.
• Heavily infested plants turn yellow and are stunted.

The main danger is that whiteflies transmit dangerous criniviruses (vein yellowing viruses), which lead to yield loss (Wehner, 2020). In some regions, whiteflies cause a physiological disorder known as "silverleaf syndrome" in courgettes, where leaves become silvery and fruits lose color (Sharma, 2016).

Prevention

• Plant seedlings at optimal times to avoid the peak whitefly population.
• Use mulch made from reflective materials — aluminum foil or silver film disorients whiteflies, reducing the number of adults in crops (Wehner, 2020).
• Remove plant debris immediately after harvest — whiteflies overwinter on it.
• Regularly check the underside of leaves. Yellow sticky traps help detect the appearance of whiteflies early (Mondal, 2020).

Control Methods

Biological. In greenhouses, the parasitoid wasp Encarsia formosa is widely used — it lays its eggs in whitefly larvae. One Encarsia destroys up to 100–200 nymphs in its lifetime. In open ground, fungal preparations Beauveria bassiana and Lecanicillium lecanii give good results (Sharma, 2016).

Mechanical. Yellow sticky traps help reduce the number of adults. However, they are useless for controlling larvae.

Chemical (last resort). The most effective are products with translaminar action — they penetrate leaf tissues and kill larvae feeding on the underside. These include spiromesifen, buprofezin, pyriproxyfen — they affect larval development but do not kill adults. To control adults, pyrethroids are used, but whiteflies quickly develop resistance, so rotating active ingredients is crucial (Kemble, 2022). Carry out all applications with thorough wetting of the underside of leaves.

Biology

Thrips have a cryptic lifestyle: females lay eggs inside leaf and fruit tissues. Larvae of two instars feed on plant sap, then drop to the soil to pupate. Under favorable conditions (warm, dry weather), a generation develops in 11–14 days, and up to 10 generations can occur per season (Mondal, 2020).

Signs and Damage

• Numerous small light spots — puncture marks — appear on leaves, then coalesce; leaves take on a silvery sheen and feel "rough" to the touch.
• Leaf margins curl downwards.
• Small, sunken spots or scars appear on fruits — traces of female oviposition. This significantly reduces marketability and storage life.
• Flowers may become deformed, and ovaries drop off.
• Severely infested plants appear stunted, with a bronzed appearance to the leaves.

In addition to direct damage, thrips spread tospoviruses — dangerous viruses causing necrosis and deformation of leaves and fruits (Wehner, 2020).

Prevention

• Regularly inspect plants, especially the underside of leaves and leaf axils.
• Control weeds, especially in row middles — they serve as thrips reservoirs.
• Use blue or white sticky traps for early detection (thrips are attracted to blue) (Mondal, 2020).
• Use healthy transplant material — thrips often "arrive" on it.
• Avoid dense plantings to improve air circulation and reduce humidity, which favors the reproduction of some species.

Control Methods

Biological. Predatory mites Neoseiulus cucumeris and Amblyseius swirskii effectively feed on thrips. The predatory bug Orius spp. — a hunter that actively preys on thrips in flowers — is also used. In protected cultivation, these predators form the basis of biological protection (Sharma, 2016).

Mechanical. Removing heavily infested leaves and flowers helps reduce pest numbers.

Chemical (last resort). For thrips control, products based on spinosad are effective — they have a biological origin (a product of soil bacteria), are of low toxicity to beneficial insects, and degrade quickly. Acetamiprid and spirotetramat are also used — these are systemic insecticides that penetrate plant tissues (Kemble, 2022). It is important to alternate active ingredients, as thrips quickly develop resistance. Treat plants in the morning or evening, paying special attention to the underside of leaves and flowers.

Biology

Slugs are nocturnal, hiding during the day under soil clods, plant debris, or in the topsoil layer. They feed on soft plant tissues, preferring young seedlings, lower leaves, and ovaries touching the ground. Wet, cool weather and abundant organic matter promote their reproduction. Slugs lay eggs in clusters under shelter, and 2–3 generations can develop per season.

Signs and Damage

• Large, irregularly shaped ragged holes appear on leaves; leaf edges are often eaten away.
• Young seedlings may be completely consumed at ground level or with damage to the growing point.
• Deep, gouged cavities appear on fruits, especially those lying on the ground, making them unfit for storage and marketing.
• A characteristic sign is the presence of shiny, slimy trails on leaves, fruits, and soil.
• Slugs are mostly active at night and in overcast weather; if you go to the field early in the morning, you can catch them "in the act."

Prevention

• Reduce humidity in plantings: avoid overcrowding, cultivate between rows to allow the soil surface to dry faster.
• Do not create shelters for slugs: promptly remove weeds, crop debris, and mulch from coarse organic materials (uncovered or loose layers of mulch serve as shelters for mollusks).
• Practice sowing on raised beds or ridges — they dry faster and are less attractive to slugs (Karataev and Sovetkina, 1984).
• Remove plant residues after harvest — they harbor eggs and adults.

Control Methods

Mechanical. Hand picking is the most environmentally friendly method, but labor-intensive. Collect slugs under shelters (boards, pieces of cardboard, wet rags) placed on the beds overnight, then removed in the morning along with the mollusks that have gathered under them. Traps with beer or sweetened water are effective — slugs are attracted to the smell of fermentation and drown.

Agronomic. Barrier strips of dry ash, fine sand, crushed eggshells, ground pine bark, or crushed brick — slugs avoid crossing dry, porous, and rough surfaces. On small plots, copper tape or wrap can be used: copper ions cause severe irritation in slugs.

Biological. Natural enemies of slugs include ground beetles, hedgehogs, shrews, frogs, and some birds. Attracting them to the plot (e.g., creating shelters for ground beetles from stones or boards) helps keep numbers in check. There are also parasitic nematodes (Phasmarhabditis hermaphrodita) that enter the slug's body and cause its death — this agent can be used in biological farming.

Chemical (last resort). Products based on ferric phosphate are safe for humans, animals, and soil biota, but effective against slugs. They act as bait: the slug eats the granules, stops feeding, and dies within a few days. Products based on metaldehyde are also available, but they are toxic to pets and many beneficial insects, so their use on food crops is severely restricted and requires strict adherence to pre-harvest intervals (Kemble, 2022).

Biology

Moths lay eggs on the underside of leaves, in leaf axils, or on young ovaries. Caterpillars pass through several instars and feed actively for 2–4 weeks, then pupate in the soil or in plant debris. In southern regions, 2–4 generations develop per season. The peak moth flight usually occurs in mid-to-late summer, when plants are well-developed but vulnerable to damage to growing points and fruits.

Signs and Damage

• Cucumber moth caterpillars live inside rolled leaves, binding them with silk. They skeletonize leaves, eating the parenchyma and leaving only a network of veins, giving them a "lace" appearance (Mondal, 2020).
• Cutworms chew large, ragged holes in leaves, may gnaw young shoots and even fruits, boring inside and causing them to rot.
• Secondary infections (fungal and bacterial rots) often appear at sites damaged by caterpillars.
• Caterpillar droppings — small dark pellets or "sawdust" — can be seen on leaves, along with characteristic chewed leaf edges.

Prevention

• Destroy weeds, especially those from the cucurbit family (wild cucumbers, vines) — they serve as pest reservoirs.
• After harvest, deeply dig or plow the area to destroy overwintering stages (pupae) and reduce numbers for the following year (Lebedeva, 1987).
• Use lightweight row covers (agrofabric, non-woven fabric) to protect young plants during moth flight periods — this physically prevents egg laying (Wehner, 2020).

Control Methods

Biological. The most well-known biopreparation is Bacillus thuringiensis (Bt). It produces a crystal toxin that affects only moth caterpillars, without harming other organisms. A caterpillar that eats a Bt-treated leaf stops feeding and dies within 1–3 days. Bt is effective against all caterpillars, including cucumber moth and cutworms (Sharma, 2016). Apply it when the first caterpillars appear, preferably in the evening, repeating treatments every 5–7 days if infestation is high.

Another biopreparation is spinosad (based on the bacterium Saccharopolyspora spinosa). It acts as a contact-stomach poison and is effective against both caterpillars and some beetles. In nature, there are also parasitoid wasps (Apanteles spp., Trichogramma spp.) that infect eggs and caterpillars — these should be preserved by avoiding broad-spectrum insecticides.

Mechanical. For low numbers, caterpillars can be picked by hand, or damaged leaves with egg masses can be removed. Using pheromone and light traps allows you to monitor the onset of moth flight and time treatments accordingly.

Chemical (last resort). If biopreparations are insufficient, insecticides from the diamide group (chlorantraniliprole, cyantraniliprole) are permissible — they are systemic and effective against caterpillars, yet relatively safe for many predatory insects (Kemble, 2022). Pyrethroid-based products (e.g., lambda-cyhalothrin) act quickly but suppress beneficial entomofauna, so their use is justified only in critical situations.

Striped Cucumber Beetle (Acalymma vittatum) and Spotted Cucumber Beetle (Diabrotica undecimpunctata)

In North America and Europe, these are the main pests of cucurbits. In Russia and CIS countries, the analogous pest is the red pumpkin beetle (Aulacophora foveicollis), widespread in southern regions and Asia (Mondal, 2020; Sharma, 2016).

Biology

Adult beetles overwinter under plant debris, in forests, or in the topsoil. In spring, they emerge, feed on seedlings and young leaves, and then lay eggs in the soil at the base of plants. Larvae live in the soil, feeding on fine roots and underground stem parts, which can cause plant wilting. After 2–4 weeks, larvae pupate, and a new generation of beetles emerges. 1–2 generations develop per year.

Signs and Damage

• Adults chew characteristic small, round holes in leaves, making them look like sieves. They also eat flower petals and can damage ovaries.
• Larvae living in the soil damage roots and stem bases, causing wilting even without visible leaf damage.
• The spotted cucumber beetle (in North America) is also a vector of bacterial wilt (Erwinia tracheiphila), which can kill the entire plantation (Wehner, 2020).

Prevention and Control Methods

• Crop Rotation. Since beetles overwinter in the soil near last year's plantings, place cucurbits in a new location every 2–3 years (Sharma, 2016).
• Destroy Plant Debris. Thoroughly incorporate plant residues after harvest to reduce the overwintering beetle population.
• Early Sowing. Young plants that have time to strengthen before the mass emergence of beetles suffer less damage. Early sowing also allows harvesting before the second wave of beetles (Pessarakli, 2016).
• Row Covers. Non-woven fabric, removed during flowering, protects seedlings from beetle feeding in the early stages.
• Biological Methods. Use preparations of Beauveria bassiana or entomopathogenic nematodes (Steinernema spp.), which infect larvae in the soil (Kemble, 2022).
• Chemical (last resort). At high numbers, use permitted insecticides — carbaryl, spinosad, lambda-cyhalothrin. Apply in the evening to minimize risk to bees (Wehner, 2020).

Other Leaf Beetles

Occasionally, flea beetles (Phyllotreta spp.) are found on courgettes, which mine leaves (creating narrow winding tunnels), and the epilachna (cotton ladybird, Epilachna chrysomelina), which skeletonizes leaves by scraping off the upper tissue. Control measures are the same as for cucumber beetles: crop rotation, weed removal, biopreparations (especially Bacillus thuringiensis for caterpillars, but it does not work on beetles; spinosad or other agents are needed here).

Biology

Click beetles lay eggs in the soil, primarily in areas occupied by grass weeds (couch grass, bluegrass) or where cereals were previously grown. Larvae actively move through the soil in search of roots and seeds. They prefer moist but not waterlogged soils and are more common in light sandy loams and loams. Both larvae and adults overwinter in the soil at a depth of 10–30 cm. With the onset of warmth, they move to the upper layers and begin feeding.

Signs and Damage

• Zucchini seedlings suddenly wilt and fall over, especially in rows bordering grassy areas.
• When pulling out a dead plant, you may notice that the roots and hypocotyl have been gnawed; sometimes roots are completely destroyed.
• Seeds, especially large ones (like those of cucurbits), may be eaten before germination.
• The wireworms themselves are easily found in the soil near damaged plants — they curl into a ring when touched.

Prevention

• Control of couch grass and other grass weeds. This is the main reservoir for wireworms. Regular weeding and cultivation between rows reduces their numbers (Lebedeva, 1987).
• Crop Rotation. Do not plant cucurbits after cereals (wheat, corn, oats) and do not place them on areas that were previously in a grass fallow.
• Deep Autumn Tillage. Fall plowing or digging to a depth of 25–30 cm brings larvae to the surface, where they die from frost or are eaten by birds (Karataev and Sovetkina, 1984).
• Traps. In spring, 1–2 weeks before sowing, bait can be placed in the soil — pieces of potato, beet, or oilcake on sticks. After a few days, the baits with the gathered wireworms are removed and destroyed.

Control Methods

Agronomic. Liming acidic soils reduces wireworm numbers, as they prefer an acidic environment. Adding ash or dolomite flour simultaneously improves plant nutrition and creates unfavorable conditions for the larvae.

Biological. In soil, wireworms are infected by entomopathogenic fungi (Metarhizium anisopliae) and nematodes (Steinernema spp., Heterorhabditis spp.). Preparations based on them can be applied to the soil at planting (Kemble, 2022). Natural enemies also include ground beetles and birds, especially starlings and rooks — attracting them to the plot reduces pest numbers.

Chemical (last resort). At high population densities and in commercial plantings, soil-applied insecticides are used at sowing: products based on bifenthrin, tebupirimfos, or imidacloprid. They are incorporated into the topsoil as granules or applied to planting holes before planting (Kemble, 2022). The use of such products in home gardens should be justified and carried out strictly according to instructions.

Biology

The mole cricket leads a hidden underground life, creating horizontal and vertical tunnels at depths of 10–20 cm, rarely up to 50–70 cm (for overwintering). It is omnivorous: it feeds on roots, tubers, seeds, small soil animals, and even earthworms. In early summer, females build a nest at a depth of 10–15 cm and lay up to 300–400 eggs, guarding them and the larvae. Young mole crickets first feed on humus, then switch to plant roots. One generation develops per season.

Signs and Damage

• Zucchini seedlings suddenly wilt, even though the soil is moist. When pulled out, the root system is found to be gnawed or completely eaten.
• Loose earthen ridges are visible on the soil surface — traces of underground tunnels. They are especially noticeable after watering or rain.
• Characteristic depressions — "burrows" — leading deep into the soil can be found around the roots.
• The mole cricket can destroy up to 100% of seedlings on small plots in just a few nights.

Prevention

• Adhere to crop rotation. The mole cricket prefers areas long occupied by a single crop.
• Deep fall plowing. Destroys nests and tunnels, while pupae and larvae brought to the surface die from frost and sun.
• Limit watering during the egg-laying period. Excessive moisture promotes mole cricket reproduction.
• Destroy weeds. Weeds provide the mole cricket with additional food and shelter.

Control Methods

Agronomic and Mechanical. In early spring, before sowing, place small piles of fresh manure — mole crickets gather in them for egg laying. After 2–3 weeks, check the piles and destroy the gathered pests. Traps made from potato or beet peels buried in the soil work similarly.

Pit traps are also effective: dig holes in the ground, fill them with moist manure or compost. Mole crickets crawl into them for wintering; in late autumn, open the pits and destroy all insects (Lebedeva, 1987).

Biological. Preparations based on entomopathogenic nematodes (Steinernema carpocapsae) actively penetrate the mole cricket's body and cause its death. They are applied to the soil with irrigation water. Predators — ground beetles, moles, lizards, birds — also keep numbers in check, although they do not fully solve the problem.

Chemical (last resort). At high populations, use insecticidal baits based on fipronil or imidacloprid, worked into the soil at tunnel depth. It is also possible to apply preparations to the planting holes at planting (Kemble, 2022). Always strictly follow the instructions, especially regarding pre-harvest intervals.

Biology

Female cockchafers burrow into the soil to a depth of 10–30 cm and lay eggs. First-year larvae feed on humus and fine roots. As they grow, they move to larger roots of plants, including cultivated ones. Larvae overwinter in deep soil layers (up to 1 m) and rise to the surface in spring. Pupation occurs at a depth of 30–50 cm, and adults emerge after 2–3 weeks. Over several years of life, a single larva can destroy the root system of many plants over a significant area.

Signs and Damage

• Zucchini, courgette, and pattypan plants are stunted, lose turgor, even with adequate watering.
• Leaves turn yellow and dry, starting from the bottom. Damage to individual bushes or parts of the field is particularly characteristic.
• When a plant is pulled out, roots are found to be gnawed or partially missing; large white larvae can be found nearby in the soil.
• Damage is most noticeable in years of mass beetle flights (usually with a 4–5 year periodicity).

Prevention

• Deep Autumn Digging. Turning the soil to a depth of 25–30 cm allows the destruction of most larvae, especially on small plots.
• Collect Adult Beetles. In May–June, during the flight period, shake cockchafers from trees early in the morning when they are sluggish, and destroy them — this reduces egg laying.
• Crop Rotation. Avoid placing cucurbits after perennial grass sods or in areas previously used for orchards or shelterbelts.
• Soil Preparation Before Planting. On small plots, larvae can be carefully hand-picked during digging before sowing.

Control Methods

Agronomic. Adding vermicompost and biohumus to the soil stimulates the development of soil microorganisms that compete with the larvae and improves plant growth, allowing them to recover better after damage. Liming acidic soils is also effective (chafer beetles prefer acidic conditions).

Biological. Entomopathogenic nematodes (Heterorhabditis bacteriophora) actively infect and destroy chafer grubs. They are applied to the soil with irrigation water, especially effectively in September–October when larvae are most active. Preparations based on the fungus Metarhizium anisopliae have also been developed (Kemble, 2022).

Chemical (last resort). Applying preparations based on imidacloprid or thiamethoxam to planting holes at planting provides root system protection for 1–2 months. At high numbers, granular insecticides may be applied to the soil (Karataev and Sovetkina, 1984). Important: many soil pest products have long pre-harvest intervals; their use on crops with a short growing season requires particular caution.