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North America and Europe, particularly the United Kingdom (UK), Germany, France, and the Netherlands, are among the leading producers of potatoes.
The continuous emergence of new pests and diseases, as well as the increasing resistance of existing threats to chemical controls, poses a significant risk to potato yields and quality. The widespread restriction of key active ingredients, such as neonicotinoids and mancozeb, further complicates control measures.
As a result, growers must adopt more sustainable and integrated pest management (IPM) strategies to mitigate these challenges.
This article provides an overview of the most pressing pest and disease threats affecting potato production across North America and Europe.
Colorado potato beetle (Leptinotarsa disseminate)
The Colorado potato beetle is one of the most notorious pests affecting potato crops. Originating in North America, this beetle has successfully spread across Europe, including Germany, the Netherlands, and France. Its remarkable ability to develop resistance to insecticides has made it a particularly difficult pest to control.
Colorado potato beetle larvae and adults feed on potato leaves, leading to extensive defoliation. This weakens the plant and reduces photosynthetic capacity, ultimately affecting tuber formation and yields.
When infestations are severe, plants can be completely stripped of foliage, resulting in total crop loss.
Historically, neonicotinoids such as imidacloprid and thiamethoxam have been effective in controlling this pest. However, resistance to these insecticides has become widespread. Other options include Spinosad-based insecticides and pyrethroids, though resistance concerns persist.
IPM strategies
- Crop rotation: Planting non-host crops such as legumes or cereals disrupts the beetle’s life cycle.
- Biological control: Fungal biopesticides such as Beauveria bassiana and entomopathogenic nematodes have shown promise.
- Pheromone traps: Utilised to monitor beetle populations and determine optimal treatment timing.
Wireworm (Agriotes spp.)
Wireworms, the larvae of click beetles, are becoming an increasing concern for potato growers, particularly in the UK and France. These pests live in the soil and cause significant damage to potato tubers.
Wireworms burrow into tubers, creating holes that make potatoes unmarketable. They also serve as entry points for secondary infections, exacerbating crop losses.
Neonicotinoid insecticides such as clothianidin have been utilised for wireworm control, but regulatory restrictions have led to a decline in their application. Newer alternatives such as fluopyram-based seed treatments are being explored.
IPM strategies
- Trap crops: Mustard and oat cover crops attract wireworms, reducing damage to potatoes.
- Biological control: Predatory nematodes and entomopathogenic fungi show potential in reducing wireworm populations.
- Soil preparation: Regular plowing exposes larvae to natural predators and desiccation.
Potato cyst nematodes (Globodera rostochiensis and G. pallida)
Potato cyst nematodes (PCN) are a major soil-borne threat to potato production, particularly in Europe.
These microscopic roundworms feed on potato roots, leading to severe plant stress and yield reductions.
Infested plants show stunted growth, yellowing foliage, and reduced tuber production. PCN cysts can remain viable in the soil for decades, making eradication extremely difficult.
Nematicides such as oxamyl and fluopyram are available but are under increasing regulatory scrutiny.
IPM strategies
- Resistant varieties: Cultivars such as Eurostar and Innovator exhibit resistance to PCN.
- Extended crop rotation: Growing non-host crops for at least four years reduces nematode populations.
- Soil testing: Identifying infestation levels before planting helps in making informed management decisions.
Aphids (Myzus persicae and Macrosiphum euphorbiae)
Aphids are soft-bodied, sap-sucking insects that serve as vectors for some of the most damaging potato viruses, including potato virus Y (PVY) and potato leafroll virus (PLRV). Because these pests can reproduce rapidly, a small infestation can quickly become an outbreak, leading to widespread virus transmission.
Aphids weaken plants by sucking sap, leading to distorted growth and yield losses. More significantly, they spread plant viruses that cause severe quality and productivity declines.
Systemic insecticides such as pymetrozine and flonicamid have been effective, though increasing restrictions on these chemicals have driven interest in alternative solutions.
IPM strategies
- Biological control: Beneficial predators such as ladybugs and lacewings naturally control aphid populations.
- Reflective mulches: Reduce aphid landings and virus transmission in potato fields.
- Companion planting: Certain plant species, such as marigolds, repel aphids and reduce the levels of infestation.
Tuber flea beetle (Epitrix tuberis)
Tuber flea beetles are an emerging problem in North America and certain European regions, particularly in warmer climates. The adult beetles feed on potato foliage, creating a characteristic ‘shot hole’ pattern, while their larvae burrow into tubers, causing internal feeding tunnels that render the potatoes unmarketable.
Infested tubers develop scarring and internal damage, making them unsuitable for sale. Severe infestations can result in total crop loss.
Farmers have traditionally relied on spinosad and pyrethroid insecticides to manage flea beetle populations, but resistance concerns have prompted interest in alternative control methods.
IPM strategies
- Field sanitation: Removing crop debris and weeds reduces breeding grounds.
- Entomopathogenic nematodes: Utilised to target soil-dwelling larvae.
- Crop rotation: Helps break the life cycle of flea beetles.
Potato psyllid (Bactericera cockerelli)
The potato psyllid is an emerging pest of major concern in North America and parts of Europe. This insect is particularly notorious for its role in transmitting zebra chip (ZC) disease, caused by the bacterium Candidatus Liberibacter solanacearum. The psyllid’s increasing range and ability to cause widespread economic damage makes it a serious threat to potato production.
Potato psyllid nymphs and adults feed on potato plants, causing leaf curling, yellowing, and stunted growth. The damage from direct feeding is compounded by the transmission of ZC, which results in severe tuber discolouration, rendering them unmarketable, particularly in processing industries. Fields with high psyllid populations can experience significant yield reductions and complete crop loss in extreme cases.
Insecticides such as abamectin, spinosad, and neonicotinoids have been utilised to control psyllid populations, but resistance has become a growing concern. Systemic insecticides applied at early infestation stages can help slow population growth, but over-reliance on chemical control increases the risk of resistance development.
IPM strategies
- Psyllid monitoring: Yellow sticky traps and regular scouting help detect early psyllid infestations.
- Biological control: Natural predators such as lacewings and parasitic wasps (Tamarixia triozae) help suppress psyllid populations. Rogueing: Removing infected plants early limits disease spread.
- Reflective mulches: These discourage psyllid landings and reduce feeding pressure on young plants.
- Timely planting: Planting early in the season can help crops develop before psyllid populations reach peak levels.
Potato tuber moth (Phthorimaea operculella)
The potato tuber moth is a serious and growing threat in warmer regions of Europe and North America, particularly in storage facilities where it continues to cause damage post-harvest. The moth lays eggs on potato plants, and its larvae burrow into tubers, making them unmarketable.
These internal feeding tunnels created by the potato tuber moth larvae lead to secondary bacterial and fungal infections. Infestations in storage facilities are especially concerning, as moth populations can increase rapidly, leading to total crop loss over time. In field infestations, the larvae can also damage foliage, causing wilting and reduced plant vigour.
Insect growth regulators and pyrethroid-based insecticides have been utilised to control tuber moth populations, but their effectiveness is limited in storage conditions. Fumigation and controlled atmosphere storage are often necessary for long-term protection.
IPM strategies
- Improved storage hygiene: Ensuring that storage facilities are clean and free of infested tubers is crucial for preventing outbreaks.
- Pheromone traps: Mating disruption using pheromone traps can significantly reduce moth populations in storage and field settings.
- Early harvesting: Harvesting potatoes before moth populations peak reduces infestation risks.
- Biological control: Bacillus thuringiensis (Bt) treatments can effectively target larvae in the field.
- Proper storage conditions: Maintaining temperatures below 10°C slows moth development and prevents rapid population growth.
Late blight (Phytophthora infestans)
Late blight has for a very long time been one of the most devastating diseases in potato production worldwide and remains to be so, causing extensive crop losses in North America and Europe.
The pathogen thrives in cool, humid conditions, leading to rapid leaf and stem infection. Symptoms include water-soaked lesions that expand and darken, eventually leading to plant collapse. Under favourable conditions, the disease can spread rapidly through airborne spores, making late blight one of the most difficult potato diseases to control.
Common fungicides include mandipropamid, fluazinam, and mancozeb (although its use is restricted in the European Union [EU]). Metalaxyl-based products were once effective but are now largely ineffective due to resistant strains of P. infestans.
IPM strategies
- Blight-resistant varieties: Cultivars such as Bionica and Sarpo Mira show high resistance.
- Weather-based forecasting: Disease prediction models help optimise fungicide application timing.
- Field sanitation: Removing infected plant debris minimises inoculum carry-over.
Early blight (Alternaria solani)
Early blight is a fungal disease that affects potato foliage, particularly in regions with warm, wet weather.
While not as destructive as late blight, it can still lead to significant yield losses if left unmanaged.
The disease first appears as small, dark brown lesions on older leaves, which expand and develop characteristic concentric rings. As the infection progresses, leaves yellow and die, reducing photosynthesis and ultimately affecting tuber size and yield. Fungicides such as difenoconazole, azoxystrobin, boscalid, and pyraclostrobin are effective when applied preventatively.
IPM strategies
- Resistant varieties: Some modern potato cultivars offer partial resistance.
- Proper spacing and air circulation: Reducing humidity in potato fields slows disease progression.
- Balanced fertilisation: Avoiding excessive nitrogen helps strengthen plant defenses against early blight.
Blackleg and soft rot (Dickeya solani and Pectobacterium spp.)
Blackleg and soft rot are bacterial diseases that cause severe losses in potato crops worldwide, particularly in wet conditions.
Blackleg affects stems, causing black, slimy decay that spreads down to the tubers. Soft rot affects tubers, leading to a foul-smelling breakdown that renders potatoes unmarketable.
The bacteria spread through contaminated seed, water, and soil. There are no effective chemical treatments for these bacterial diseases.
IPM strategies
- Use of disease-free seed: Ensuring seed potatoes are certified and disease-free reduces infection risks.
- Field hygiene: Cleaning equipment and avoiding working in wet fields reduce bacterial spread.
- Crop rotation: Reducing pathogen buildup in the soil helps control outbreaks.
Common scab (Streptomyces scabies)
Common scab is a widespread bacterial disease that affects potato tubers, reducing their quality for fresh consumption and processing.
The disease manifests as rough, corky lesions on the tuber surface.
While it does not impact yield, affected potatoes are often rejected in markets where skin appearance is important. No effective bactericides or fungicides exist for controlling common scab.
IPM strategies
- Soil moisture management: Maintaining consistent soil moisture during tuber initiation helps prevent infection.
- Acidifying fertilisation: Sulphur applications lower soil pH, creating unfavourable conditions for S. scabies.
- Resistant varieties: Some potato varieties, such as Russet Burbank, are less susceptible to scab.
Powdery scab (Spongospora subterranea)
Powdery scab is a soil-borne disease that damages tubers and serves as a vector for potato mop-top virus (PMTV).
Infected tubers develop shallow, powdery lesions that lower their market value. The disease is especially problematic in waterlogged soils and regions with high humidity.
There are no effective chemical controls available for powdery scab.
IPM strategies
- Resistant varieties: Certain varieties exhibit partial resistance to powdery scab.
- Improved drainage: Reducing soil moisture lowers disease severity.
- Crop rotation: Avoiding planting potatoes in the same field for several years reduces pathogen buildup.
Silver scurf (Helminthosporium solani)
Silver scurf is a fungal disease that affects the potato skin, reducing its marketability. The disease causes silver-gray discoloration of tubers, particularly in storage. While it does not impact yield, it makes potatoes less appealing to consumers and increases dehydration during storage.
Fungicides such as thiabendazole (TBZ), fludioxonil, and imazalil are utilised for post-harvest treatment.
IPM strategies
- Proper storage conditions: Keeping tubers dry and cool slows disease spread in storage.
- Seed treatment: Applying fungicides to seed potatoes before planting reduces infection risk.
- Shorter storage periods: Reducing storage duration limits disease progression.
Bacterial wilt (Ralstonia solanacearum)
Bacterial wilt is a serious disease that affects a wide range of crops, including potatoes. It is more common in tropical and subtropical regions but is increasingly being detected in temperate climates, including parts of Europe.
The disease causes wilting of potato plants, accompanied by black vascular discolouration in stems and tubers. Infected tubers rot from the inside, making them unmarketable.
There are no effective chemical treatments for bacterial wilt.
IPM strategies
- Quarantine measures: Avoiding the introduction of infected seed or soil prevents outbreaks.
- Resistant varieties: Some breeding programmes have developed partially resistant varieties.
- Crop rotation: Rotating with non-host crops such as maize reduces soil inoculum levels.
Verticillium wilt (Verticillium dahliae and Verticillium albo-atrum)
Verticillium wilt is a soil-borne fungal disease that affects a wide range of crops, including potatoes. It is prevalent in North America and Europe, particularly in regions with warm summers.
The disease causes gradual wilting and yellowing of lower leaves, leading to stunted plant growth. The vascular system becomes blocked by fungal spores, restricting water movement within the plant. Over time, infected plants exhibit uneven tuber development and reduced yields.
There are no effective fungicides for controlling Verticillium wilt in potatoes.
IPM strategies
- Crop rotation: Long rotations with non-host crops such as cereals reduce soil inoculum.
- Resistant varieties: Certain cultivars have shown partial resistance.
- Soil fumigation: In severely infested fields, soil fumigation with chloropicrin may help reduce pathogen levels.
- Soil testing: Monitoring Verticillium levels before planting can help determine risk levels.
Fusarium dry rot (Fusarium spp.)
Fusarium dry rot is a major storage disease that affects harvested potato tubers. The disease is caused by several species of the Fusarium fungus and is particularly problematic in storage facilities with poor ventilation.
Dry rot results in sunken, wrinkled lesions on tubers. Over time, the affected areas develop dry, powdery decay. Severe infections can lead to complete tuber breakdown, rendering them unmarketable. The disease also increases susceptibility to secondary bacterial infections.
Fungicide treatments such as TBZ are commonly applied to seed potatoes before planting to reduce the risk of infection.
IPM strategies
- Proper storage conditions: Maintaining low humidity and cool temperatures (4 to 6°C) slows disease progression.
- Seed treatment: Applying fungicides to seed potatoes before planting helps prevent early infection.
- Wound healing: Allowing tubers to cure properly before storage minimises entry points for infection.
- Sanitisation: Regular cleaning of storage facilities and handling equipment reduces contamination.
Black dot (Colletotrichum coccodes)
Black dot is a fungal disease that affects both potato foliage and tubers. It has become more prevalent in recent years, particularly in the UK, France, and the Netherlands, where intensive potato cultivation occurs.
Infected plants exhibit yellowing and early senescence, leading to premature vine death and reduced tuber size. On tubers, black dot appears as small, black specks on the skin, which worsen during storage. While it does not cause direct decay, the disease reduces marketability and storage quality.
Fungicides such as azoxystrobin and boscalid provide moderate control when applied early in the growing season.
IPM strategies
- Crop rotation: Avoiding continuous potato cropping reduces disease pressure.
- Resistant varieties: Some cultivars are less susceptible to black dot.
- Minimising stress: Proper irrigation and fertilisation help maintain plant vigour and reduce susceptibility.
- Soil testing: Identifying fungal presence before planting helps growers take preventive measures.
Emerging threats
In recent years, potato farmers in North America and Europe have faced new and emerging threats that pose significant risks to yield and quality. These emerging threats are driven by a combination of climate change, global trade, evolving pathogen populations, and increased pesticide resistance.
Some of these threats are new diseases and pests spreading into new regions, while others are existing problems becoming more aggressive or harder to control due to chemical resistance or regulatory limitations. The following is an in-depth look at the most prevalent and concerning emerging threats in potato production.
Zebra chip disease (Candidatus Liberibacter solanacearum)
ZC is a serious emerging disease in North America and parts of Europe, where it is transmitted by the potato psyllid (Bactericera cockerelli). First detected in Mexico and the United States (US), the disease has spread into Canada and has been reported in parts of Europe, raising alarm among growers.
The disease causes internal discolouration of potato tubers, resulting in dark streaks that worsen when fried, making the potatoes unmarketable. Affected plants show symptoms such as leaf curling, yellowing, and early senescence, leading to reduced yields. Infected tubers are rejected by processors and fresh markets, making this one of the most economically damaging emerging diseases.
Insecticides such as abamectin, spinosad, and neonicotinoids are utilised to target the psyllid vector, but resistance is developing.
IPM strategies
- Psyllid monitoring: Sticky traps and scouting are utilised to detect early infestations.
- Beneficial insects: Parasitic wasps and lacewings help reduce psyllid populations.
- Rogueing: Infected plants should be removed to prevent further spread.
Virulent late blight strains (new Phytophthora infestans genotypes)
Late blight (Phytophthora infestans) has always been a major concern for potato growers, but new, more aggressive genotypes are emerging in North America and Europe. In particular, the EU_43_A1 strain has raised concerns due to its higher resistance to fungicides and faster infection cycle.
These new strains cause rapid defoliation, leading to entire field loss within days if conditions are favourable. The disease is spreading faster, surviving longer in soil and volunteers, and showing reduced sensitivity to metalaxyl-based fungicides, making it harder to control.
Mandipropamid, cymoxanil, fluazinam, and propamocarb are currently effective against some strains. Resistance monitoring is crucial to determine which fungicides remain effective.
IPM strategies
- Blight-resistant varieties: Sarpo Mira and other resistant cultivars provide partial protection.
- Strict field sanitation: Removing volunteer potatoes reduces pathogen carry-over.
- Weather-based forecasting: Disease prediction models help optimise fungicide application timing.
Climate-driven disease shifts
Warmer temperatures and shifting weather patterns are expanding the range of pests and diseases, making regions more vulnerable to threats that were previously uncommon.
Examples include:
- Potato tuber moth (Phthorimaea operculella), historically a problem in warm regions, is now appearing in southern Europe and warmer US states.
- Bacterial wilt (Ralstonia solanacearum), previously limited to tropical regions, is now detected in temperate parts of Europe, including southern France.
- PVY strains are evolving, making existing resistant varieties less effective.
A sustainable approach
While chemical control remains an essential tool in potato disease and pest management, increasing regulatory restrictions, resistance development, and environmental concerns have led to more strategic chemical use.
As the global potato industry faces mounting challenges from pests, diseases, regulatory restrictions, and climate change, IPM has become the foundation of modern sustainable agriculture. It focusses on prevention, monitoring, and targeted actions to maintain pest and disease populations at levels that do not cause significant economic damage.
The ultimate goal of IPM is to reduce reliance on chemical inputs while ensuring stable and high-quality potato yields.
Emerging innovations in IPM include:
- RNA-based pesticides: New developments in gene-silencing technology could help target specific pests such as Colorado potato beetle without harming beneficial insects.
- AI and remote sensing: Drones and AI-driven data analytics are improving pest detection and monitoring, allowing for site-specific interventions.
- Gene-edited potatoes: CRISPR technology is being explored to develop potato varieties with built-in resistance to late blight, nematodes, and viruses. – Lukie Pieterse, editor and publisher, Potato News Today
For more information, email the author at lukie@potatonewstoday.com.