Pests

2.1. Aphids (Aphididae): The Main Virus Vectors

Signs of Appearance. Aphids are tiny (1–2 mm) insects that usually settle in large colonies on the underside of leaves, on shoot tips, and sometimes on flowers (McLeod and Rashid, 2016). The most noticeable sign of their presence is the sticky honeydew they excrete. Sooty mold ("black fungus") quickly develops on this honeydew, covering the leaves with a black coating and further impairing their photosynthesis. Leaves begin to curl, turn yellow, and deform (Akhatov et al., 2013).

Life Cycle. Aphids reproduce at an astonishing rate. In warm weather, females give birth to live larvae without fertilization. One female can produce up to 80–100 offspring in her lifetime, and the new generation can reproduce within a week (Mondal et al., 2020). More than 10 generations can occur in a single season. In summer, winged individuals appear, which fly off and colonize new plants.

Damage Caused.

1. Direct Damage: By sucking sap, aphids deplete the plant. Leaves lose turgor, curl, and shoots become deformed (Akhatov et al., 2013).

2. Contamination: Honeydew and sooty mold disrupt the process of photosynthesis, reducing yield and deteriorating fruit quality.

3. Virus Transmission: This is the most dangerous aspect. Aphids are vectors of more than 50 viruses, including Cucumber Mosaic Virus (CMV) and Watermelon Mosaic Virus (WMV). Losses from viral diseases can be total (McLeod and Rashid, 2016; Wehner et al., 2020).

Prevention.

• Weed Control: Many aphid species overwinter on weed plants (sow thistle, chickweed, goosefoot) (Akhatov et al., 2013).
• Attracting Beneficial Insects: Plant nectar-bearing plants (dill, fennel, buckwheat) near cucumbers to attract lacewings, ladybugs, and hoverflies—active predators of aphids.
• Silver or Reflective Mulch: This mulch disorients winged aphids searching for plants and reduces the likelihood of them landing on the bed (Wehner et al., 2020).
• Balanced Nutrition: Avoid over-fertilizing cucumbers with nitrogen fertilizers. Excess nitrogen makes plant tissues juicier and more attractive to aphids.

Control Methods.

• Biological: The safest and most effective method. Use specialized parasites—Aphidius colemani and Lysiphlebus testaceipes. These tiny wasps lay their eggs inside aphids, turning them into immobile "mummies" (Akhatov et al., 2013). The predatory gall midge Aphidoletes aphidimyza, whose larvae actively eat aphids, is also effective. In greenhouses, ladybugs Cycloneda and lacewings are often used, but their effectiveness is lower than that of specialized parasites.
• Mechanical: With a small number of pests, they can be washed off with a strong jet of water. This is effective but temporary.
• Biopesticides: Insecticides based on the fungi Lecanicillium longisporum and Beauveria bassiana infect aphids without harming beneficial insects or humans (Akhatov et al., 2013). Their application requires high humidity (around 90%).
• Chemical: Use only as a last resort, and use products with systemic or translaminar action, e.g., based on imidacloprid (Confidor, Iskra Zolotaya) or thiamethoxam (Aktara). These substances penetrate plant tissues and kill aphids even on the underside of leaves. However, they are dangerous to bees, so do not apply them during flowering. Keep in mind that aphids quickly develop resistance, so alternate products from different chemical classes (Gahukar, 2016).

2.2. Spider Mite (Tetranychus urticae): The Hidden Threat

The spider mite is not an insect but an arachnid. It is one of the most dangerous pests of cucumber, especially in hot, dry weather, both in greenhouses and in open ground (Wehner et al., 2020).

Signs of Appearance. Mites are very small (0.3–0.5 mm) and difficult to see with the naked eye. The first sign is tiny pale yellow puncture spots on the leaves (McLeod and Rashid, 2016). With mass reproduction, the leaves become mottled, bronze, or brown, then dry up and fall off. A characteristic sign is fine webbing on the underside of leaves, between stems, and on shoot tips, where the mites establish colonies (Mondal et al., 2020).

Life Cycle. Adult females overwinter under plant debris, in soil, and in cracks in greenhouses. In spring, they lay eggs on the underside of leaves. Up to 10–15 generations develop per season (Akhatov et al., 2013). The optimal temperature for reproduction is 30°C with humidity of 45–55%. In dry, hot weather, mites multiply explosively.

Damage Caused. Mites puncture leaf cells and suck out their contents, including chlorophyll. This disrupts photosynthesis. Severely damaged plants drop their leaves, leading to sunburn of the fruit and a sharp reduction in yield (Mondal et al., 2020). Mites can also transmit fungal diseases.

Prevention.

• Regular Watering and Spraying: Mites do not like humid air. In hot, dry weather, it is helpful to do refreshing water sprays, especially on the underside of leaves.
• Destruction of Plant Debris: Remove and burn all plant debris after harvest.
• Balanced Fertilizing: Excess nitrogen and lack of phosphorus make plants more attractive to mites.
• Planting Resistant Varieties: There are varieties that are more resistant to spider mites.

Control Methods.

• Biological: The most effective and safest method. Use the predatory mite Phytoseiulus persimilis. This aggressive predator feeds on spider mites at all stages of development. One female Phytoseiulus can destroy up to 20–30 mites and their eggs per day (Akhatov et al., 2013). It should be released as soon as the first foci of the pest appear.
• Biopesticides: Use products based on avermectins (Fitoverm, Akarin). They effectively kill mites but do not kill eggs. Therefore, treatment must be repeated after 5–7 days to destroy the new generation. The fungi Neozygites floridana, Lecanicillium muscarium, and Beauveria bassiana are also effective.
• Chemical: As a last resort, use specialized acaricides (Actellik). Mites quickly develop resistance to chemicals, so their use requires extreme caution and rotation of products (Gahukar, 2016). Treatments should be carried out ensuring the underside of leaves is thoroughly wetted.

2.3. Whitefly (Aleyrodidae): The Greenhouse Scourge

The whitefly is a small white insect (1–1.5 mm) resembling a tiny moth. In greenhouses and plastic covers, it can be the main pest (Akhatov et al., 2013). It is less common in open ground but can be a threat during hot summers.

Signs of Appearance. When the plant is touched, clouds of tiny white flies rise up. On the underside of leaves, yellowish eggs, immobile scale-like larvae, and adults can be seen. A second characteristic sign is honeydew, as with aphids, on which sooty mold develops. The leaves become sticky and turn black (Pantielev, 1986).

Life Cycle. The female lays up to 200 eggs on the underside of leaves. The larvae go through several stages; the last stage (nymph) is immobile. The adult insect emerges from it. Up to 10–15 generations can develop in a greenhouse per year.

Damage Caused. Like other sucking pests, the whitefly sucks sap, weakening the plant. The honeydew it exudes covers the leaves, disrupting photosynthesis. Furthermore, the whitefly is a vector of dangerous viruses, e.g., Cucumber Vein Yellowing Virus (CVYV) and others (Akhatov et al., 2013).

Prevention.

• Quarantine: Carefully check all seedlings brought into the greenhouse. Whiteflies are often introduced with new plants.
• Weed Control: Remove all weeds in and around the greenhouse.
• Barriers: Install fine mesh on ventilation openings to prevent whiteflies from entering.
• Yellow Sticky Traps: Whiteflies are attracted to the color yellow. These traps work well both for monitoring and for mass trapping of adults (Wehner et al., 2020).

Control Methods.

• Biological: The specialized parasite—Encarsia formosa. This tiny black wasp lays its eggs in whitefly larvae. Infected larvae turn black and die. For effective control, Encarsia must be released regularly in the greenhouse. The parasite Eretmocerus eremicus is also used.
• Predators: The bug Macrolophus nubilis is an active predator that feeds on both whiteflies and aphids.
• Biopesticides: The fungi Lecanicillium muscarium and Beauveria bassiana are effective against whitefly larvae and adults at high humidity. However, they do not affect eggs, so repeated treatments are necessary.
• Chemical: In greenhouses, systemic products (Aktara, Confidor) are applied through watering (Gahukar, 2016). It is important to remember that whiteflies are resistant to many insecticides, so their use should be extremely limited.

2.4. Thrips (Thripidae): Dangerous Polyphagous Pests

Thrips are very small insects (up to 2 mm) with elongated bodies. In recent years, they have become a serious problem on cucumbers, especially in greenhouses (Akhatov et al., 2013). The most dangerous are onion thrips (Thrips tabaci) and western flower thrips (Frankliniella occidentalis)—the latter being a quarantine pest.

Signs of Appearance. Small silvery-white streaks or spots appear on the leaves (McLeod and Rashid, 2016). These are puncture sites where thrips inject their saliva and suck out sap. With severe damage, leaves take on a silvery sheen, become deformed, and dry out. Corky growths and spots appear on the fruit, which become deformed (Gahukar, 2016). Black dots (excrement) are often visible on the leaves.

Life Cycle. The female lays eggs in leaf tissue. Larvae emerge from them and feed on the leaves. They then go into the soil to pupate. Up to 6–8 generations develop per season.

Damage Caused. Thrips damage not only leaves but also flowers and fruit. Their feeding leads to reduced photosynthesis, fruit distortion, and loss of marketable quality. Western flower thrips is a vector of Tomato Spotted Wilt Virus (TSWV), which can completely destroy the crop.

Prevention.

• Destruction of Plant Debris and deep autumn plowing, as many thrips species overwinter in the topsoil.
• Quarantine: Western flower thrips is often introduced with seedlings and cut flowers.
• Blue Sticky Traps: Unlike many other pests, thrips are better attracted to blue rather than yellow. Use them for monitoring (Akhatov et al., 2013).

Control Methods.

• Biological: Predatory mites Neoseiulus cucumeris and Neoseiulus barkeri are used to control thrips. They feed on young thrips larvae. Predatory bugs Orius (Orius majusculus, O. laevigatus) are active hunters that eat both larvae and adult thrips.
• Biopesticides: The fungi Beauveria bassiana and Metarhizium anisopliae effectively suppress thrips.
• Chemical: The product Spintor (based on spinosad) is effective against thrips. It is of biological origin and safe for many beneficial insects. Chemical options include Actellik, Vertimek, and Akarin. Because thrips are resistant, treatments should be carried out at intervals of 5–7 days, rotating products. Application of systemic insecticides through watering also gives good results (Gahukar, 2016).

This concludes the chapter on sucking pests. Ready to write chapter "3. Leaf-Eating Pests"?

Continuing our practical guide. After sucking pests, we move on to those that cause mechanical damage by gnawing out tissues of leaves, stems, and fruits.

3.1. Caterpillars (Lepidoptera)

Caterpillars are the larval stage of butterflies and moths. Several species can be found on cucumbers, the most common being the melon/cotton bollworm, the cucumber moth (or pickleworm), and various cutworms that eat leaves (Mondal et al., 2020). Cabbage cutworm and cabbage white butterfly caterpillars can also cause severe damage if cucumber is grown near cabbage (Pantielev, 1986).

Signs of Appearance. The most obvious sign is chewed leaves. Caterpillars may eat the entire leaf blade, leaving only the skeleton of veins, or make large and small irregular holes in the leaves (Mondal et al., 2020). Dark green or black caterpillar droppings can be seen on leaves and near the plants. Caterpillar activity increases in the evening and at night; during the day, they often hide under leaves or in the topsoil.

Life Cycle. Butterflies lay eggs on the underside of leaves. Young caterpillars emerge from the eggs and go through several stages (instars), gradually increasing in size. Adult caterpillars go into the soil to pupate and transform into pupae, from which the butterfly of the next generation emerges.

Damage Caused. Leaf damage leads to a reduction in photosynthetic area, weakening the plant and reducing yield. Caterpillars of some species, e.g., cucumber moth (Diaphania indica), can damage not only leaves but also ovaries and young fruits. They bore inside, making them unfit for consumption (Gahukar, 2016). Outbreaks of caterpillars can lead to complete defoliation of plantings.

Prevention.

• Deep Autumn Plowing: This destroys the overwintering stages (pupae) of most species (Wehner et al., 2020).
• Destruction of Plant Debris: After harvest, be sure to collect and burn all plant residues where pupae and eggs may overwinter.
• Regular Inspection of Plants: Especially the underside of leaves, where egg masses and young caterpillars are most often found.
• Attracting Birds: Insectivorous birds (tits, sparrows, starlings) are excellent helpers in controlling caterpillars. Hang feeders and nest boxes.

Control Methods.

• Mechanical Collection: The safest and most environmentally friendly method for small areas. Regularly inspect leaves and manually collect and destroy egg masses and caterpillars.
• Biological: Use the bacterial product Bitoxibacillin (BTB) or Lepidocid. These products contain spores of the bacterium Bacillus thuringiensis, which affects only butterfly caterpillars, causing intestinal paralysis and death. They are absolutely safe for humans, bees, and other beneficial insects (Gahukar, 2016). It is important to apply them at the beginning of caterpillar emergence, as the product affects young individuals.
• Attracting Entomophages: To control some caterpillar species, small parasitic wasps (e.g., Apanteles) are used. They can be attracted by planting nectar-bearing plants.
• Chemical: Use only during mass caterpillar infestations. Registered products for private farms (LPH) include Actellik, Karbofos, or Iskra. However, remember that they are toxic to beneficial insects. Carry out treatments in the evening, carefully spraying both sides of the leaves (Pantielev, 1986).

3.2. Beetles and Their Larvae (Coleoptera)

Among Coleoptera, the most dangerous on cucumbers are various species of leaf beetles, primarily the Colorado potato beetle, cucumber beetles, and their larvae (Mondal et al., 2020). In regions with hot climates, cucumbers can be damaged by red blister beetles and chafers (Mondal et al., 2020). The greatest danger is posed by beetles that damage seedlings and young plants.

Signs of Appearance. The main sign is chewed leaves, stems, and flowers. Adult beetles and their larvae may eat the leaf blade completely or along the edges, make holes in the leaves, and also damage roots and stems at the base. Seedlings may be eaten entirely (Mondal et al., 2020). The beetles themselves, which often have bright coloration, can be seen on the leaves.

Life Cycle. Adult beetles overwinter in the soil or under plant debris. In spring, they emerge, feed, and mate. Females lay eggs in the soil or on leaves. Larvae emerge from the eggs (including the bright orange larvae of the Colorado potato beetle), which initially also feed on plants but may eventually go into the soil to pupate.

Damage Caused. The greatest damage is caused by larvae and adults of the Colorado potato beetle and cucumber beetles. They can completely destroy seedlings, especially at early stages (Mondal et al., 2020). Damaged leaves lose their ability to photosynthesize, sharply reducing yield. Some beetles, e.g., cucumber beetles (Acalymma vittatum), are also vectors of bacterial wilt (bacteriosis), making them particularly dangerous (Wehner et al., 2020). Click beetle larvae—wireworms—are also dangerous; they live in the soil and gnaw at roots.

Prevention.

• Crop Rotation: Do not plant cucumbers in the same place for several years in a row to prevent pest accumulation.
• Deep Plowing: Autumn plowing destroys the overwintering stages of beetles (Mondal et al., 2020).
• Weed Control: Many beetles (including Colorado potato beetle) live on weeds (nightshades, amaranths), so timely weeding reduces the threat.
• Use of Traps and Trap Crops: Some beetle species are attracted to bright colors or the scent of certain plants. For example, for cucumber beetles, trap plantings of cucurbit bait plants can be used, and then the pests on them can be destroyed (Wehner et al., 2020).

Control Methods.

• Mechanical Collection: For the Colorado potato beetle, this is the simplest and most effective method. Early morning or evening, when the beetles are less active, collect them and their larvae in a container with kerosene or salt water.
• Biological: Entomopathogenic nematodes (e.g., Steinernema carpocapsae) and the fungus Beauveria bassiana are used to control Colorado potato beetle larvae and other soil pests (Mondal et al., 2020). However, their effectiveness in open ground may be lower due to weather conditions.
• Trap Trenches and Barriers: Trenches with loose soil can be made around the beds to trap moving larvae and adult beetles (McLeod and Rashid, 2016).
• Chemical: The use of insecticides (Actellik, Karate, Decis) is permissible only during mass reproduction. It is important to observe the waiting periods before harvest.

3.3. Slugs and Snails (Gastropoda)

Slugs and snails are not insects but gastropod mollusks. They love damp weather and often annoy gardeners in rainy years or under irrigation conditions (Mondal et al., 2020). On cucumbers, they can damage not only leaves but also fruits, making them unsuitable for storage and consumption.

Signs of Appearance. The most characteristic sign is silvery slime trails on leaves and stems, as well as on the soil. Irregular holes and chewed edges appear on leaves and fruits (Mondal et al., 2020). Slugs and snails are active mainly at night and in cloudy, rainy weather; during the day, they hide under stones, boards, or in the top layer of moist soil.

Life Cycle. Slugs lay eggs in moist soil, under plant debris, or in cracks in the ground. Young individuals emerge from the eggs and grow and reproduce throughout the warm season. Adults overwinter in the soil (Akhatov et al., 2013).

Damage Caused. Slugs can cause great damage to young seedlings by eating them completely. On adult plants, they damage leaves and ovaries and can bore into fruits, leaving deep gnawed cavities (Mondal et al., 2020). Damaged fruits lose their marketable appearance and quickly rot.

Prevention.

• Timely Weeding: Remove weeds that serve as shelter for slugs.
• Elimination of Shelters: Remove boards, stones, old leaves, and other debris from the site where slugs can hide.
• Mulching: Use mulch from straw, sawdust, or dry grass. Slugs do not like to move on dry, prickly surfaces. However, mulch from fresh grass may attract them, so preference should be given to dry mulch (Gahukar, 2016).
• Morning Watering: If you water the beds in the morning, the soil will have time to dry out by evening, reducing humidity and making the area less attractive to slugs.

Control Methods.

• Mechanical Collection: In the evening or early morning, collect slugs by hand or using traps (pieces of cardboard, damp rags they crawl under during the day). Destroy collected pests.
• Traps: Containers buried in the ground with beer or yeast solution attract and drown slugs (McLeod and Rashid, 2016).
• Using Barriers: Around the beds, strips of sharp flour, eggshells, ash, or crushed eggshells can be scattered. This creates a mechanical barrier that slugs cannot cross.
• Biological Methods: Garden slugs are food for many animals: ground beetles, hedgehogs, frogs, birds. Attract them to your garden.
• Chemical: There are safe products based on iron phosphate (e.g., "Slug Killer"). They are non-toxic to humans and pets but effectively kill slugs. Apply them according to the instructions.

In this chapter, we examined the main leaf-eating pests. In the next part, we will move on to soil pests—those that hide in the ground and threaten the underground organs of the plant.

4.1. Wireworms (Click Beetle Larvae)

Wireworms are the larvae of click beetles (Elateridae). They got their name from their hard, thin, elongated yellowish-brown body, which resembles a piece of wire (Mondal et al., 2020). These larvae live in the soil and are serious pests of many crops, including cucumber (Akhatov et al., 2013).

Signs of Appearance. Above-ground signs include wilting and stunted growth. Examination of the root system may reveal gnawed tunnels, damaged roots, and dark feeding marks. Larvae can damage both young rootlets and the main root, penetrating inside and making it non-functional (Kotov and Adritskaya, 2016). Seedlings and young plants are particularly affected, and can be gnawed through at the soil surface.

Life Cycle. Click beetles lay eggs in the soil, usually in moist, organic-rich soil. Larvae develop in the soil for 3 to 5 years, going through several stages. The most harmful are the larvae of older stages (3rd–4th year of life). Pupation occurs in the soil, and the adult beetle emerges to the surface (Akhatov et al., 2013). Wireworms overwinter in the soil at a depth of 10–20 cm.

Damage Caused. Damaged roots absorb water and nutrients poorly. The plant begins to wilt, especially on hot days; growth slows down; leaves turn yellow. With severe damage, seedlings may die. Wireworms prefer moist, acidic soils and areas overgrown with couch grass, so they are often found on heavy soils (Mondal et al., 2020).

Prevention.

• Liming Acidic Soils: Wireworms do not like alkaline environments.
• Eradication of Couch Grass: This weed is a favorite habitat for wireworms.
• Deep Digging and Loosening: Autumn digging to a depth of 20–25 cm brings larvae to the surface, where they die from frost or are eaten by birds (Akhatov et al., 2013). Spring loosening is also effective.
• Crop Rotation: Do not plant cucumbers after potatoes, corn, or perennial grasses, where wireworms often accumulate (Gahukar, 2016).

Control Methods.

• Baits and Traps: Place pieces of raw potato, carrot, or beet in the soil at a depth of 5–10 cm, mark the spots with sticks, and after 2–3 days collect the wireworms that have gathered. Repeat the procedure several times during the season (Kotov and Adritskaya, 2016).
• Biological Methods: Entomopathogenic fungi Metarhizium anisopliae and Beauveria bassiana are effective and infect larvae in the soil (Akhatov et al., 2013). Nematodes Steinernema carpocapsae can also be used, which actively seek out and destroy wireworms.
• Chemical: With a high pest population, insecticides (e.g., based on diazinon) can be applied to the soil during planting or between rows (Gahukar, 2016). However, these products are toxic, so their use must be strictly justified.

4.2. Mole Cricket (Gryllotalpa gryllotalpa)

The mole cricket is a large (up to 5–6 cm) brown insect with powerful front digging limbs resembling mole paws. It lives in the soil, creating complex tunnel systems both near the surface and at depth (Akhatov et al., 2013). It is most dangerous in southern and central regions but is also found further north.

Signs of Appearance. The most obvious sign is winding, loose earthen ridges on the soil surface that appear after rain or watering (Kotov and Adritskaya, 2016). The entrance holes to the burrows are round. Plants begin to wilt, especially on hot days, and examination of the roots reveals gnawed stems at the soil surface and damaged roots. The mole cricket can also damage young fruits if they touch the ground (Mondal et al., 2020).

Life Cycle. Adult mole crickets overwinter in the soil at a depth of up to 1–2 meters. In spring, they emerge to the surface, mate, and lay eggs in a nest at a depth of 10–15 cm, which resembles a small earthen ball. The larvae (similar to adults but wingless) develop for about a year, feeding on the underground parts of plants. One generation develops per year (Akhatov et al., 2013).

Damage Caused. The mole cricket can gnaw through the roots and stems of young plants, destroying seedlings. On adult plants, it damages the root system, reducing yield. It can also damage fruits, especially when they come into contact with the soil (Mondal et al., 2020). The mole cricket is omnivorous and can cause great damage in small areas.

Prevention.

• Deep Digging in autumn and spring destroys nests and tunnels.
• Weed Control reduces breeding and hiding places.
• Early Sowing and Planting allows plants to become stronger before the mole cricket emerges (Gahukar, 2016).
• Attracting Birds and Insectivorous Animals: Starlings, rooks, and hedgehogs actively eat mole crickets.

Control Methods.

• Poisoned Baits: The most popular control methods. Chopped potato or corn kernels are boiled and sprayed with insecticides (e.g., based on karbofos), then placed at a depth of 2–3 cm in mole cricket tunnel areas (Kotov and Adritskaya, 2016).
• Traps: In autumn and spring, pits (30–40 cm deep) are dug, filled with manure, and covered with a board. Mole crickets gather in these pits for wintering and can be destroyed. Jars buried in the ground with beer or sweet water are also used (Akhatov et al., 2013).
• Biological Methods: The fungus Metarhizium anisopliae infects mole crickets. However, its effectiveness in open ground may be reduced.
• Chemical: In case of mass spread, granular insecticides based on diazinon or fenthion are used, applied to the soil or in baits. It is important to strictly follow the instructions (Gahukar, 2016).

4.3. Root-Knot Nematodes (Meloidogyne spp.)

Root-knot nematodes are microscopic roundworms that are a serious problem for cucumbers, especially in greenhouses and on light soils (Akhatov et al., 2013). They attack the root system, causing the formation of swellings—galls.

Signs of Appearance. The above-ground part of the plant appears stunted: yellowing leaves, stunted growth, wilting during hot hours (Akhatov et al., 2013). Examination of the roots reveals characteristic spherical or spindle-shaped thickenings (galls) of various sizes (Mondal et al., 2020). In advanced cases, galls may fuse and form large singalls.

Life Cycle. Female nematodes lay eggs in a gelatinous sac that remains on the surface of the gall. Larvae (juveniles) hatch from the eggs, penetrate the roots, where they cause cell proliferation, forming galls. New females and males develop inside the galls; the cycle is completed in 3–4 weeks under favorable conditions (temperature 20–30°C) (Akhatov et al., 2013).

Damage Caused. Galls disrupt the functioning of the root system, preventing normal absorption of water and nutrients. The plant experiences constant stress, yield decreases, and fruit quality deteriorates. Secondary infections (fungal and bacterial) readily attack weakened plants. Yield losses from nematodes can reach 30–50% (Mondal et al., 2020; Gahukar, 2016).

Prevention.

• Quarantine: Carefully check planting material (seedlings, bulbs) for galls.
• Using Resistant Varieties: There are cucumber hybrids with genetic resistance to root-knot nematodes (Mondal et al., 2020). This is the most effective method.
• Proper Crop Rotation: Return cucumbers to the same place no earlier than after 3–4 years.
• Destruction of Plant Debris: Burn diseased plants to prevent nematode spread.
• Pre-Planting Soil Preparation: Steam treatment of soil in greenhouses or the use of biopreparations (e.g., Purpureocillium lilacinum) can reduce nematode numbers (Akhatov et al., 2013).

Control Methods.

• Biological: Use antagonistic fungi (Purpureocillium lilacinum, Pochonia chlamydosporia) that attack nematode eggs and larvae (Akhatov et al., 2013). The bacterium Pasteuria penetrans is also effective.
• Agrotechnical: Provocative watering (creating favorable conditions for larval emergence) followed by their death, sowing green manure (e.g., mustard, oilseed radish) as intermediate crops—this reduces nematode numbers (Akhatov et al., 2013).
• Chemical: In greenhouses, products based on avermectins (Fitoverm, Akarin) are used for soil treatment. However, this is an expensive method and does not always give 100% results.

4.4. Other Soil Pests

In addition to wireworms, mole crickets, and nematodes, other insects can also damage cucumber roots. These include:

• Hoverfly Larvae (Syrphidae): Sometimes damage roots, especially in greenhouses, where they are difficult to remove.
• Fungus Gnat (Bradysia brunnipes): Damages in greenhouses, especially with excessive moisture. Larvae feed on roots and can cause plant wilting (Akhatov et al., 2013). Control measures: maintaining optimal humidity, using yellow sticky traps to catch adults.
• Weevil Larvae: Some species of root weevils can damage roots.
• Millipedes and Wireworms: Occasionally found in soil, especially in waterlogged areas, and can damage young roots.

General principles for protecting against soil pests include a set of agrotechnical measures (proper crop rotation, soil treatment, application of organic fertilizers), the use of biological products, and, in exceptional cases, the application of insecticides. The main thing is not to allow pests to multiply and destroy the crop.

5.1. Agrotechnical Methods—The Foundation of Protection

Agrotechnology is the foundation of plant health. A strong, healthy cucumber plant withstands pest attacks much better than a weakened one. All agrotechnical measures are aimed at creating conditions in which pests feel uncomfortable, while plants, on the contrary, receive everything they need for growth and development.

Crop Rotation. Cucumbers should not be grown in the same place for several years in a row. This leads to the accumulation of specific pests (nematodes, fungal diseases) and their larvae and overwintering stages in the soil (Mondal et al., 2020). The optimal interval for returning cucumbers to the same place is at least 3–4 years (Gahukar, 2016). It is desirable that the preceding crops are not affected by the same pests (legumes, onions, cabbage, early potatoes).

Correct Site Selection and Soil Preparation. The site should be well-lit and warm. Deep autumn plowing (25–30 cm) destroys the overwintering stages of many pests: wireworms, chafer larvae, butterfly pupae (Akhatov et al., 2013; Pantielev, 1986). Spring cultivation also helps destroy eggs and larvae laid in the topsoil.

Maintaining Optimal Planting Density. Dense plantings create favorable conditions for the rapid spread of pests and diseases due to high humidity and poor ventilation. Follow the recommended planting scheme for your cucumber variety (Pantielev, 1986).

Regular Soil Loosening. This operation not only improves aeration but also destroys mole cricket tunnels and destroys the larvae and pupae of many insects in the surface layer.

Balanced Nutrition. Excess nitrogen fertilizers make plant tissues succulent and attractive to sucking pests (aphids, mites). In contrast, phosphorus and potassium fertilizers increase plant resistance to diseases and stress (Wehner et al., 2020). Apply fertilizers according to recommended rates and plant needs at different growth stages.

Proper Watering. Watering with cold water or excessive watering weakens the root system and makes plants vulnerable to soil pests. Water only with warm water and maintain optimal humidity (Akhatov et al., 2013). In hot weather, refreshing watering can help reduce spider mite numbers, but avoid waterlogging.

Weed Control. Weeds are reservoirs for pests. Aphids, spider mites, thrips, whiteflies, and other pests initially colonize weeds and then move to cultivated plants (Mondal et al., 2020). Timely weeding is a crucial preventive measure.

5.2. Biological Control—Smart Helpers

Using living organisms to suppress pests is the most environmentally friendly and safe method, becoming increasingly popular both on farms and on small plots.

Entomophages and Acariphages. These are predatory insects and mites that feed on pests.

• The predatory mite Phytoseiulus persimilis is used against spider mites. It reproduces 1.5–1.9 times faster than the pest, allowing it to effectively suppress its population (Akhatov et al., 2013).
• Against aphids, the parasitic wasps Aphidius colemani and Lysiphlebus testaceipes are effective, as is the predatory gall midge Aphidoletes aphidimyza (Akhatov et al., 2013; Gahukar, 2016).
• To destroy whiteflies, the parasite Encarsia formosa is used (Wehner et al., 2020). This is one of the most successful stories of biological control in greenhouses.
• Against thrips, predatory mites Neoseiulus cucumeris and bugs Orius are effective (Akhatov et al., 2013).

Microbiological Products. These are products based on bacteria, fungi, or viruses that infect insects.

• The bacterium Bacillus thuringiensis (Bt) is effective against butterfly caterpillars (Pantielev, 1986; Gahukar, 2016). Products based on it (Bitoxibacillin, Lepidocid) are safe for humans, bees, and beneficial insects.
• The fungi Beauveria bassiana, Lecanicillium muscarium, and Metarhizium anisopliae are effective against aphids, whiteflies, thrips, spider mites, and soil pests (wireworms) (Akhatov et al., 2013). These products require high humidity for maximum effectiveness.
• The fungus Purpureocillium lilacinum is used to control root-knot nematodes. It infects nematode eggs and larvae, reducing their numbers in the soil (Akhatov et al., 2013).
• Entomopathogenic nematodes Steinernema carpocapsae are effective against wireworms, chafer larvae, and other soil pests (Mondal et al., 2020).

5.3. Mechanical Methods—Simple and Reliable Weapons

These are the simplest and most accessible methods that require no special skills or the purchase of expensive products. They are especially effective on small plots.

• Manual Collection. Regularly inspect plants and collect egg masses, caterpillars, Colorado potato beetle larvae, mole crickets, and slugs. Destroy them by placing them in a container with soapy water or kerosene (Pantielev, 1986).
• Shaking. Early in the morning, when pests are inactive, beetles and caterpillars can be shaken from plants onto a sheet and destroyed.
• Barriers and Traps. Use yellow and blue sticky traps to catch whiteflies, thrips, and other flying pests (Wehner et al., 2020). Against slugs, use barriers of sharp flour, eggshells, or ash, as well as beer traps (McLeod and Rashid, 2016).
• Washing with Water. A strong jet of water can wash aphids, spider mites, and other sucking pests from the leaves. This method provides a temporary effect but helps reduce pest numbers.

5.4. Chemical Means—The Last Line of Defense

Chemical insecticides and acaricides are powerful weapons, but they should be used with caution and only as a last resort, when other methods no longer work or when pest numbers exceed the economic injury level (Gahukar, 2016).

Principles of Using Chemical Means:

• Product Selection: Use only those products registered for use on cucumbers and in private farms.
• Dosage Compliance: Strictly follow the instructions. Overdosing does not enhance the effect but can cause plant burns and accumulation of toxic substances in the fruit.
• Treatment Timing: Carry out treatments in the early morning or evening to avoid sunburn. Avoid treatments during flowering to avoid harming bees.
• Waiting Period: Observe the waiting periods (the time between treatment and harvest) indicated in the instructions. This ensures product safety.
• Rotation: Regularly alternate products from different chemical classes to prevent the development of pest resistance (Gahukar, 2016). For example, systemic insecticides (Aktara, Confidor) are effective against aphids but should not be used too often.
• Spot Treatment: Treat not all plants, but only pest foci. This saves products and preserves beneficial insects.

5.5. Monitoring and Decision-Making—The Key to Success

Integrated protection is not just a set of methods but a decision-making system. The gardener must regularly inspect their plantings to detect pest appearance in time and assess the scale of the problem. This allows the right decision to be made: is it time to use biopreparations, or can one still get by with manual collection and agrotechnical methods?

Practical Action Algorithm:

1. Regular Inspection: Dedicate 10–15 minutes to inspecting plants daily or every other day. Pay attention to the underside of leaves, where aphids, mites, and egg masses hide.

2. Situation Assessment: If you notice a few pests but they are not causing visible damage, start with preventive measures and mechanical collection.

3. Transition to Active Methods: If pest numbers are increasing and the first signs of damage appear (leaf curling, yellow spots, chewed edges), apply biological products or release entomophages.

4. Last Resort: Only if biological methods do not yield results or the pest is multiplying rapidly and threatens crop loss, apply chemical means, strictly observing safety rules (Gahukar, 2016).

Integrated cucumber protection against pests is an ongoing process requiring attention, knowledge, and patience. But it provides the main benefit—the ability to obtain a healthy and abundant harvest without unnecessary risks to health and the environment.

Mistake 1: Incorrect Pest Identification

This is the most common and dangerous mistake. Gardeners often confuse the damage caused by different pests and apply ineffective measures. For example, spider mite damage (tiny light spots and webbing) is mistaken for disease or lack of moisture, and silvery streaks from thrips are mistaken for sunburn (Mondal et al., 2020).

Why it's a mistake. Without the correct diagnosis, it is impossible to choose the right protection strategy. Insecticides for aphids do not work against mites, and products for caterpillars are useless against sucking pests. As a result, you waste time, money, and effort treating a non-existent problem while the real pest continues to destroy the crop.

How to do it correctly. Carefully inspect plants with a magnifying glass or magnifier. Pay attention to the nature of the damage, the pest's habitat, and, if possible, its appearance. Use the tables and descriptions in this article for accurate identification. In doubtful cases, consult with specialists or look for information in reliable sources.

Mistake 2: Neglecting Prevention

Many gardeners only start fighting pests after they have already appeared and caused noticeable damage. Preventive measures (crop rotation, deep digging, weed control, attracting beneficial insects) are often ignored.

Why it's a mistake. Prevention is the cheapest and most effective way to protect. It creates conditions in which pests find it difficult to multiply and plants remain healthy and strong. Once a pest has appeared, fighting it is much more difficult and expensive, and crop losses are inevitable (Gahukar, 2016).

How to do it correctly. Make prevention a regular practice. Include mandatory activities in your gardening calendar: crop rotation, autumn and spring soil treatment, timely weeding, fertilizing with balanced fertilizers. Plant according to recommended schemes and avoid dense plantings.

Mistake 3: Applying Chemical Products at the Wrong Time

The most common mistake is treating plants during hot, sunny hours, during flowering, or immediately before harvest (Gahukar, 2016).

Why it's a mistake. Treatment during hot hours can cause burns to leaves and fruits. Applying chemicals during flowering kills bees and other pollinators, leading to a sharp decline in yield (McLeod and Rashid, 2016). Violation of waiting periods (between treatment and harvest) leads to the accumulation of toxic substances in the fruit, making them hazardous to health.

How to do it correctly. Carry out treatments in the early morning or evening when the sun is not active. Never spray plants during flowering. Strictly observe the waiting periods indicated in the product instructions. If harvesting has already begun, use only biological products with short waiting periods (e.g., Fitoverm or biopreparations based on Bacillus thuringiensis).

Mistake 4: Excessive Use and Incorrect Product Rotation

Some gardeners, when any pest appears, immediately reach for strong insecticides, using them repeatedly and randomly (Gahukar, 2016). Others use the same product several times in a row without changing it.

Why it's a mistake. Continuous use of potent pesticides kills beneficial insects, disrupts ecological balance, and leads to pest outbreaks. Insects and mites quickly develop resistance (resistance) to chemical products, especially to products of the same class (Gahukar, 2016). As a result, after 2–3 generations, the products stop working, and you have to look for increasingly stronger and more dangerous means.

How to do it correctly. Use chemical products only as a last resort when biological and mechanical methods are no longer effective. Be sure to alternate products from different chemical classes (e.g., once based on imidacloprid, next time based on pyrethroids). Study the active ingredient, not just the product name. Use the minimum effective dosages specified in the instructions.

Mistake 5: Underestimating Biological Methods

Many gardeners are still skeptical about biopreparations and entomophages, considering them insufficiently reliable. They prefer the familiar, albeit more dangerous, "chemicals."

Why it's a mistake. Modern biological products and biological control agents are highly effective and, when used correctly, are in no way inferior to chemical ones. They are safe for humans, beneficial insects, and the environment, do not cause resistance, and do not disrupt the ecosystem (Akhatov et al., 2013; Gahukar, 2016).

How to do it correctly. Actively incorporate biological methods into your practice. Start with prevention and attracting beneficial insects. Use biopreparations based on bacteria and fungi (Bitoxibacillin, Lepidocid, Fitoverm) at the first signs of pests. For greenhouses, be sure to use entomophages (Phytoseiulus, Encarsia, Aphidius)—this is the most effective and safe way to protect.

Mistake 6: Ignoring Pest Resistance

Some gardeners believe that if they bought an imported, "strong" product, it will always be effective against all pests.

Why it's a mistake. Resistance to pesticides is an evolutionary process. In every pest population, there are individuals with some degree of resistance to chemical products. With continuous use of the same product, it is these individuals that survive and pass on their resistance to offspring. After several generations, the product stops working (Gahukar, 2016).

How to do it correctly. Regularly alternate products with different mechanisms of action. Do not use the same product twice in a row within a single season. Carefully read the instructions and pay attention to the active ingredient, not the trade name. Combine chemical treatments with biological and mechanical methods to reduce selective pressure on pest populations.

Mistake 7: Improper Watering and Care

Watering with cold water, excessive moisture, insufficient soil loosening, and over-fertilizing with nitrogen—all this can contribute to the development of pests and diseases (Mondal et al., 2020).

Why it's a mistake. Waterlogging creates favorable conditions for the development of fungal diseases and many soil pests such as fungus gnats and rot bacteria (Akhatov et al., 2013). Cold water and temperature fluctuations weaken the root system and make plants vulnerable to sucking pests. Excess nitrogen leads to excessive growth of succulent foliage, attracting aphids (Wehner et al., 2020).

How to do it correctly. Water cucumbers only with warm water (not below 20–22°C). Maintain optimal humidity levels, avoiding waterlogging and drying out. Regularly loosen the soil to ensure air access to the roots. Apply mineral fertilizers in a balanced manner, with a predominance of phosphorus and potassium during the fruiting period.