Potatoes are susceptible to a variety of pests and diseases that can severely impact yield and quality. At POMAIS Agriculture, we offer effective solutions for managing these challenges with a wide range of pesticide products. Additionally, we provide customized pesticide formulations by combining multiple active ingredients to address specific potato crop needs, ensuring optimal protection and a healthy harvest.

Common Potato Diseases

1. Late Blight (Phytophthora infestans)

Impact:
Late blight is one of the most devastating diseases for potato crops, causing rapid decay of the leaves, stems, and tubers. It can spread quickly, especially under cool, wet conditions, and lead to substantial crop loss.

Symptoms:

  • Dark, water-soaked lesions on leaves and stems, often surrounded by a yellow halo.
  • White, cotton-like growth under wet conditions, particularly on the undersides of leaves.
  • Tuber rot, which leads to the production of dark, sunken lesions on the tubers.

Control Methods:

  • Critical Control Period: From the early vegetative stage to the tuber formation period.
  • Recommended Pesticides: Fungicides like Mancozeb, Copper-based fungicides, and Metalaxyl are effective in controlling late blight.

2. Early Blight (Alternaria solani)

Impact:
Early blight is a fungal disease that affects both leaves and stems, leading to reduced photosynthesis and poor tuber development. In severe cases, early blight can cause premature defoliation and yield loss.

Symptoms:

  • Concentric, dark brown or black spots with yellow halos on older leaves.
  • Lesions that enlarge, causing tissue necrosis.
  • Defoliation leading to poor growth and decreased yield.

Control Methods:

  • Critical Control Period: During early to mid-growing season.
  • Recommended Pesticides: Fungicides such as Azoxystrobin or Chlorothalonil are effective in controlling early blight.
Mancozeb
Mancozeb

Mancozeb

Metalaxyl 35% WP
Metalaxyl-M 124 gL + Azoxystrobin 322 gL SE
Metalaxyl-M 37.5 gL + Chlorothalonil 500 gL SC

Main Potato Diseases and Management Recommendations

Bacterial ring rot is a seed-borne vascular disease that causes wilt and internal tuber decay. Infected plants show yellowing and wilting of lower leaves, with creamy, cheese-like rot forming a distinct ring in the tuber’s vascular tissue. When pressure is applied, creamy ooze may appear from the cut surface.
When it appears: During mid to late growth, particularly if contaminated seed or equipment is used. It can persist for years on unclean tools and containers.
Management: There is no curative treatment. Prevent introduction by planting certified disease-free seed, disinfecting equipment, and destroying infected lots. Copper bactericides can slightly suppress surface bacteria but are not systemic. Rotation and hygiene are critical.

These bacteria attack the stems and seed pieces, producing a soft, foul-smelling decay. Blackleg symptoms include black, slimy stems, wilted leaves, and poor stands from decayed seed pieces.
When it appears: Early season under cool, wet soil followed by warm weather. Poor aeration and mechanical injury accelerate infection.
Management: Use well-suberized seed, avoid planting in water-logged soils, and ensure seed cutters and planters are disinfected daily. Warm seed before cutting and apply fungicidal seed treatments containing fludioxonil or thiabendazole to reduce secondary rots. Keep storage temperatures below 10 °C and maintain airflow.

A soil-borne fungus that forms minute black dots (microsclerotia) on tubers and stems. Infected plants exhibit premature vine death and reduced tuber size.
When it appears: Common late in the season, especially following stress such as drought or heavy early blight infection.
Management: Employ 3–4-year rotations, avoid continuous potato cropping, and improve soil drainage. Fungicides containing azoxystrobin, boscalid, or penthiopyrad applied to soil or foliage can reduce incidence.

“Calico” describes a mosaic pattern of light and dark green patches on leaves, caused by mixed infections (often PVY and Alfalfa mosaic virus). It reduces photosynthetic efficiency and tuber yield.
When it appears: Anytime during growth but most visible from mid-season. Spread mainly by aphids.
Management: Plant certified seed; remove infected plants; control aphid vectors with imidacloprid, acetamiprid, or flupyradifurone; eliminate weedy virus reservoirs.

Causes a dry, gray-black rot at the stem base, with tiny black sclerotia that resemble charcoal dust. It develops in hot, dry soils when plants are water-stressed.
When it appears: Late season, especially in sandy fields with high temperature and low humidity.
Management: Maintain irrigation, increase organic matter, and rotate with non-host crops (cereals). No reliable fungicides exist, but azoxystrobin or flutolanil can suppress outbreaks.

Produces corky or raised lesions on tuber surfaces, making them unsightly though not decayed. Infection occurs as new tubers form.
When it appears: During tuber initiation in warm, dry soils with high pH (>5.2).
Management: Maintain consistent soil moisture for 2–4 weeks after tuber set, avoid fresh manure, and apply acidifying fertilizers. No chemical control is fully effective; focus on irrigation and crop rotation.

The disease causes brown concentric rings inside the tuber and mild leaf chlorosis. It’s transmitted by stubby-root nematodes.
When it appears: In sandy soils with nematode populations, visible at harvest.
Management: Control nematode vectors using fluopyram, fosthiazate, or oxamyl, and rotate away from host crops. Clean seed and nematode testing are recommended.

Results in mottled, distorted leaves and yield reduction. Aphids transmit CMV non-persistently.
When it appears: Warm seasons with high aphid movement.
Management: Use virus-free seed, remove alternate hosts, and suppress aphids with systemic insecticides such as imidacloprid or thiamethoxam. Mineral oil sprays can help reduce transmission.

Symptoms include leaf curling, thickened brittle foliage, and purple discoloration. Plants are severely stunted and often produce no tubers.
When it appears: When beet leafhopper populations migrate into potato fields, usually in dry, warm weather.
Management: Apply lambda-cyhalothrin or deltamethrin early in migration periods, manage weeds that harbor vectors, and use tolerant cultivars where available.

Caused by wall-less bacteria spread by leafhoppers. Symptoms are yellow or purple leaves, multiple small shoots (“witches’ broom”), and deformed tubers.
When it appears: Warm periods favoring leafhopper activity.
Management: Suppress leafhoppers, eliminate weeds, and remove infected plants. There is no chemical cure once infected.

Produces characteristic “target-spot” concentric rings on lower leaves, leading to premature defoliation.
When it appears: From canopy development through maturity, especially under dry stress followed by humidity.
Management: Use protectant fungicides (chlorothalonil, mancozeb) starting early, rotating with QoI (azoxystrobin), SDHI (boscalid, fluopyram), or DMI (difenoconazole). Maintain nitrogen balance and remove old crop debris.

Causes shriveled seed pieces and internal dry cavities in stored tubers, with brownish, dry rot and concentric rings.
When it appears: At cutting and during storage.
Management: Cut and plant promptly; disinfect knives; treat seed with fludioxonil or thiabendazole; store at 3–4 °C with 90% humidity and good airflow.

Infected plants show yellowing of lower leaves and one-sided wilt. Cutting stems reveals vascular browning.
When it appears: Mid to late season in continuous potato fields.
Management: Rotate with non-hosts for 4 years, maintain balanced irrigation, and control nematodes that worsen symptoms. No chemical cure is available.

The most devastating potato disease. Causes water-soaked lesions on leaves, stems, and tubers, with white sporulation under humid conditions. Tubers rot in field and storage.
When it appears: Cool (10–20 °C), wet weather with long leaf wetness periods.
Management: Start fungicide protection before forecasted infection periods. Rotate oxathiapiprolin, mandipropamid, cyazofamid, cymoxanil + chlorothalonil, or fluazinam. Eliminate cull piles and volunteer potatoes to reduce inoculum.

Leaves roll upward and become brittle; tubers may develop internal net necrosis. Transmitted by aphids.
When it appears: Mid to late season after aphid buildup.
Management: Certified seed, aphid control (flupyradifurone, acetamiprid), and removal of infected plants.

Show mottled, rugose, or streaked leaves, stunting, and reduced tuber set. Spread by aphids and infected seed.
When it appears: Throughout the season.
Management: Clean seed, vector control, removal of volunteer plants, and virus-resistant varieties.

Tuber flesh turns pink after exposure to air, then brown or black. Often causes post-harvest storage leaks.
When it appears: Waterlogged soils near harvest and warm storage.
Management: Improve drainage, avoid over-irrigation, and apply phosphorous acid or oxathiapiprolin before harvest. Store dry, cool, and well-ventilated tubers.

Creates raised pustules on tubers and root galling. The pathogen also transmits potato mop-top virus.
When it appears: In cool, wet soils during tuber initiation.
Management: Long rotations (5+ years), improved drainage, and partial protection from fluazinam seed treatments. Avoid infested fields.

Causes watery, soft rot starting at wounds, often with a musty odor.
When it appears: During warm, wet harvest and early storage.
Management: Harvest only under dry conditions, cool quickly to below 10 °C, and avoid bruising. Mefenoxam/metalaxyl can protect wounded tubers when applied at harvest.

Forms white cottony mycelium and small mustard-seed sclerotia at the stem base, leading to wilting.
When it appears: Hot, humid weather, especially in southern regions.
Management: Deep plowing, crop rotation, and flutolanil or azoxystrobin soil treatment reduce inoculum.

Causes shiny silver patches on stored tubers; severe infections lead to shriveling and weight loss.
When it appears: Late season and during long storage at high humidity.
Management: Apply thiabendazole, fludioxonil, or imazalil seed and post-harvest treatments; reduce humidity and improve ventilation in storage.

Results in uneven emergence, brown lesions on stolons, and black sclerotia (“dirt that won’t wash off”) on tubers.
When it appears: Cool, wet soil conditions after planting.
Management: Treat seed or soil with flutolanil, pencycuron, sedaxane, or penflufen. Avoid cold planting and improve drainage.

Causes one-sided wilt and yellowing, with vascular browning in stems. Yield losses increase when combined with nematodes.
When it appears: Mid to late season in old potato soils.
Management: 3–4 year rotations, nematode control, and resistant cultivars. Soil fumigation may help where permitted.

Produces soft, water-soaked lesions on stems and foliage, with fluffy white mycelium and black sclerotia.
When it appears: Cool, humid conditions around flowering and vine closure.
Management: Increase canopy ventilation, control irrigation, and apply boscalid, fluazinam, penthiopyrad, or iprodione at early bloom. Remove plant debris after harvest.

Imidacloprid
Thiamethoxam25%SC
Acetamiprid20%SP

Common Potato Pests

1. Colorado Potato Beetle (Leptinotarsa decemlineata)

Impact:
The Colorado potato beetle is a major pest that attacks both the foliage and stems of potato plants. Its feeding results in defoliation and can significantly reduce crop yield. The beetles also carry viruses that can further affect plant health.

Symptoms:

  • Defoliation of leaves, resulting in reduced photosynthesis.
  • Presence of yellowish larvae and adult beetles on the undersides of leaves.
  • Stunted growth and poor tuber development due to the loss of foliage.

Control Methods:

  • Critical Control Period: From the early vegetative stage through to tuber maturity.
  • Recommended Pesticides: Insecticides such as Imidacloprid, Thiamethoxam, and Pyrethroids are effective in controlling the Colorado potato beetle.

2. Aphids (Macrosiphum euphorbiae)

Impact:
Aphids are sap-feeding insects that cause direct damage by sucking nutrients from the plants, which weakens the plants and results in yellowing and stunted growth. They are also vectors for several viral diseases.

Symptoms:

  • Yellowing and wilting of leaves.
  • The presence of aphids on the undersides of leaves.
  • The secretion of honeydew, which attracts sooty mold.

Control Methods:

  • Critical Control Period: From seedling stage to tuber maturity.
  • Recommended Pesticides: Systemic insecticides like Imidacloprid and Acetamiprid can control aphid populations effectively.

Key Insect Pests of Potato and Recommended Control

Description: Small soft-bodied insects that suck sap from leaves and stems, causing leaf curling, yellowing, and transmitting viral diseases like PVY and PLRV.
Occurrence: Usually appear from early vegetative to tuber bulking stages, especially under warm, dry conditions.
Recommended Insecticides:

  • Imidacloprid (systemic, long-lasting protection)

  • Acetamiprid or Thiamethoxam (contact and systemic)

  • Pymetrozine (anti-feeding effect, ideal for resistance management)

Description: Small, wedge-shaped insects that feed on potato leaves and transmit Purple Top and Aster Yellows phytoplasma.
Occurrence: Active during warm seasons; adults migrate into potato fields from nearby weeds.
Recommended Insecticides:

  • Lambda-cyhalothrin or Deltamethrin (quick knockdown)

  • Imidacloprid (systemic protection in early season)

  • Thiamethoxam + Lambda-cyhalothrin mixtures for extended control

Description: Caterpillars that hide in soil during the day and feed at night, cutting young stems near the soil surface.
Occurrence: Most damaging during early crop establishment and cool, moist spring conditions.
Recommended Insecticides:

  • Chlorpyrifos (soil treatment before planting)

  • Lambda-cyhalothrin or Cypermethrin (foliar application at night)

  • Indoxacarb or Emamectin benzoate (targeting larvae)

Description: Tiny, jumping beetles that chew small round holes (“shot holes”) in leaves, reducing photosynthesis and vigor.
Occurrence: Appear soon after emergence and persist through early growth.
Recommended Insecticides:

  • Imidacloprid or Clothianidin (seed or soil treatment)

  • Deltamethrin (contact spray for adults)

  • Spinosad (for resistance rotation, lower residue profile)

Description: Small sap-sucking insect that transmits zebra chip disease caused by Candidatus Liberibacter solanacearum.
Occurrence: From mid-season onward in warm, dry weather; populations increase rapidly if not managed early.
Recommended Insecticides:

  • Abamectin or Spirotetramat (target nymphs and adults)

  • Imidacloprid or Flupyradifurone (systemic, long-lasting control)

  • Bifenthrin (fast knockdown for heavy infestations)

Description: Moth larvae bore into tubers and leaves, creating galleries and increasing storage losses.
Occurrence: Common in late season and during warm, dry storage conditions.
Recommended Insecticides:

  • Chlorantraniliprole (effective on larvae)

  • Emamectin benzoate or Lufenuron (egg and larval control)

  • Bacillus thuringiensis (Bt) for eco-friendly programs

Description: Tiny white insects found on undersides of leaves; cause chlorosis, sooty mold, and transmit viruses.
Occurrence: Thrive under high temperature and dense canopy, mostly during mid to late season.
Recommended Insecticides:

  • Pyriproxyfen or Buprofezin (juvenile hormone inhibitors)

  • Imidacloprid or Thiamethoxam (systemic protection)

  • Spiromesifen or Flupyradifurone (for resistance management)

Description: Hard-bodied larvae of click beetles that feed on potato tubers, creating tunnels and reducing market quality.
Occurrence: Persistent in fields with previous grass cover or poor rotation; damage occurs from planting to tuber bulking.
Recommended Insecticides:

  • Fipronil or Chlorpyrifos (soil treatment before planting)

  • Tefluthrin (granule formulation at seeding)

  • Imidacloprid (seed treatment for light infestations)

Impact of Potato Pests and Diseases

The presence of pests and diseases in potato crops can lead to severe consequences:

  • Yield Loss: Diseases like late blight and pests like the Colorado potato beetle can result in a significant reduction in yield.
  • Quality Degradation: Fungal diseases like early blight can damage the appearance and quality of the potatoes, leading to a decrease in marketability.
  • Disease Transmission: Pests like aphids can spread viral diseases, which can cause widespread crop damage.
  • Crop Failure: In severe cases, unchecked pest and disease infestations can result in total crop loss.

Potato Pest and Disease Management Solutions

Control Indicators:

  • Early Detection: Monitoring for signs of pests and diseases at every growth stage is critical to prevent widespread damage.
  • Preventive Treatments: Applying fungicides and insecticides before the onset of severe infestations can help maintain crop health.

Critical Control Periods:

  • Seedling to Early Vegetative Stages: Control of pests such as aphids and the prevention of early blight is crucial during this stage.
  • Tuber Formation to Maturation: Protecting plants from late blight and the Colorado potato beetle is essential during the later stages of growth.

Recommended Pesticides:

  • Fungicides: Mancozeb, Metalaxyl, Azoxystrobin, and Chlorothalonil are effective in controlling late and early blight.
  • Insecticides: Imidacloprid, Thiamethoxam, Acetamiprid, and Pyrethroids are recommended for controlling potato pests such as the Colorado potato beetle and aphids.

About Us

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Whether you’re expanding into new markets or developing your own product line, our team is here to provide flexible, scalable solutions for your business.

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