What kind of pest is a stem potato nematode?


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Description of the Pest

Plant parasitic nematodes are microscopic roundworms that feed on plant roots. They live in soil and plant tissues, and more than one species may occur in a field. They have a wide host range, and vary in their environmental requirements, the symptoms they cause, and the risk to potatoes.


Overwintering root-knot nematode juveniles invade roots and later tubers, establish feeding sites, and develop into the adult stage. Adult females are swollen, sedentary, and lay eggs in a gelatinous matrix on or just below the root surface. Second-stage juveniles (J2) hatch from these eggs and move through the soil to invade other roots and tubers. When no crop is present, the nematodes survive as eggs or J2, which can be found in the soil. Root-knot nematode feeding reduces the vigor of plants and causes blemishes on tubers. The latter can lead to a severe reduction in tuber quality and, as a result, affected potatoes become unmarketable. Lesion nematodes damage roots by feeding and moving through cortical tissues. In addition, Pratylenchus penetrans increases the susceptibility of potato plants to Verticillium wilt and blemishes tubers. Pratylenchus neglectus is common in potato fields but has not been shown to damage potatoes in California. Stubby root nematodes feed on root surfaces, and can result in formation of numerous stubby roots. Yield loss has not been reported. The major problem caused by this nematode species is transmission of tobacco rattle virus, which causes corky ringspot disease on developing tubers.


The symptoms described below are indicative of a nematode problem but are not diagnostic because they could result from other causes as well. In general, aboveground symptoms include stunted, yellowed, chlorotic, and/or dead plants. Infected plants are likely to wilt earlier under temperature or moisture stress. Infestations may occur without causing any aboveground symptoms.

Feeding by root-knot nematode causes characteristic swellings, called galls, on roots. Galls caused by Meloidogyne chitwoodi are small and difficult to see. On heavily infested plants, egg masses appear as tiny round bumps on feeder roots. Meloidogyne hapla causes small distinct galls with proliferation of lateral roots around these galls. Meloidogyne incognita causes more pronounced galls. All three species of Meloidogyne and Pratylenchus penetrans cause bumps, warts, or crosslike fissures on the surface of infected tubers. However, those caused by M. hapla are less distinct. Brown spots develop inside tubers, mostly in the outer 0.25 inch (6 mm), which are visible when a thin layer of tuber is peeled off. Lesion nematodes cause reddish brown lesions on the roots that turn black later. Stubby root nematodes cause numerous short and stunted (stubby) roots, and corky ringspot symptoms on tubers if the nematode is carrying TRV.

Field Evaluation

To make management decisions, it is important to know the nematode species present and their population estimates. If a previous crop had problems caused by nematodes that are also listed as pests of potato, their numbers may be high enough to cause damage to subsequent potato crops. Soil samples should be sent to a diagnostic laboratory for enumeration and identification.

Take soil samples in fall from within the root zone of the previous crop after harvest or, preferably, just before harvest. Divide the field into sampling blocks of not more than five acres. Each block should be representative of the field’s cropping history, crop injury, or soil texture. Take several subsamples randomly from a block, mix them thoroughly and make a composite sample of about 1 quart (1 liter) for each block. (See UC ANR Publication 3316, Integrated Pest Management for Potatoes, for more details.) Place the samples in separate plastic bags, seal them, and place a label on the outside with your name, address, location, and the current/previous crop and the crop you intend to grow. Keep samples cool (do not freeze), and transport them as soon as possible to a diagnostic laboratory. Contact your farm advisor to help you find a laboratory for extracting and identifying nematodes, and for help in interpreting sample results.


Meloidogyne chitwoodi, Columbia root-knot nematode, has caused significant crop damage in high organic matter soils at low densities in Modoc and Siskiyou counties. In fields where this root-knot nematode is a problem, long-term integrated management tactics such as crop rotation, cultural controls, fumigation, and nematicides are necessary to prevent a substantial devaluation of the crop due to nematode-induced tuber blemishes.

Fumigants (metam sodium and 1,3-dichloropropene) and non-fumigant nematicides (ethoprop and oxamyl) are chemical control options for minimizing Columbia root-knot nematode crop damage in soils with low organic matter content. However, in silty clay loam soil with high organic matter when Columbia root-knot numbers exceed 500 second stage juveniles (J2) per 1000cc of soil, neither 1,3-dichloropropene nor metam sodium provide acceptable levels of control.

The following management tactics for Columbia root-knot nematode may increase efficacy in high organic matter soils):

  • A combination of fumigation (1,3-dichloropropene) and application of non-fumigant nematicide (oxamyl) can be effective. However, using this combination has not been tested in Californian in high organic matter soils.
  • Metam sodium broadcasted and immediately incorporated using a rotary tiller. (Based on one year of research.)
  • Multiple depth injection of 1, 3-dichloropropene or metam sodium

For other nematode species there are no precise guidelines for economic threshold levels under California cropping conditions. Fields infested with stubby root nematodes and tobacco rattle virus have been found in Monterey and Kern counties and in the Santa Maria area of Santa Barbara County. Fields with known virus infestations should not be planted to potatoes without an effective control strategy in place for stubby root nematode, which can transmit the virus that causes corky ringspot in potato.


The following measures will help prevent spread of nematodes to uninfested fields: (1) using certified planting material; (2) cleaning soil from equipment before moving between fields; (3) keeping irrigation water in a holding pond so that any nematodes present can settle out and pumping water from near the surface of the pond; (4) preventing/ reducing animal movement from infested to uninfested fields; and (5) composting manure to kill any nematodes that might be present before applying it to fields.

Crop Rotation

Crop rotation can be useful in reducing nematode numbers except of stubby root nematode and the tobacco rattle virus which have wide host range and so crop rotation is not practical. Alfalfa is not a host of M. chitwoodi, Race 1; cereals are nonhosts of M. hapla; and there are several nematode resistant tomato varieties that can be used if M. incognita is a problem. Research in the Pacific Northwest has shown that cover crops of rapeseed, mustard, oilseed radish, or sudangrass reduce numbers of root-knot nematodes when incorporated as green manure. At present there are no nematode resistant potato varieties available. For managing Columbia root-knot nematode, consult the UC Nematology website.

Cultural Control

Fields that are left fallow but kept weed-free usually have an 80 to 90% per year reduction in root-knot nematode populations. Infested tubers left in the field after harvest can be a source of inoculum. Destroy potato plants that subsequently emerge from these tubers to restrict nematode reproduction. Avoid storage of tubers infected by M. chitwoodi as blemishes can increase during storage.

Common name Amount per acre REI‡ PHI‡
(Example trade name) (hours) (days)
Pesticide precautions Protect water Calculate VOCs Protect bees
Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least likely to cause resistance are at the top of the table. When choosing a pesticide, consider information relating to the pesticide’s properties and application timing, honey bees, and environmental impact. Always read the label of the product being used.
(Vapam HL) 37.5–75 gal See label NA
(Sectagon 42) 30–75 gal See label NA
COMMENTS: Contact your farm advisor for advice on the most effective application method for a particular situation. Fumigants such as metam sodium and 1, 3-dichloropropene are a prime source of volatile organic compounds (VOCs), which are a major air quality issue.
(Mocap EC) Maximum label rate See label NA
COMMENTS: Contact your farm advisor for information on maximizing the effectiveness of this material.
(Telone II) Label rates See label NA
COMMENTS: Helps to control lesion nematode, which is associated with Verticillium wilt and stubby root nematode, which is associated with corky ringspot. Fumigants such as metam sodium and 1, 3-dichloropropene are a prime source of volatile organic compounds (VOCs), which are a major air quality issue.
(Vydate C-LV) Label rates 48 7
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.
* Permit required from county agricultural commissioner for purchase or use.
NA Not applicable
§ Do not exceed the maximum rates allowed under the California Code of Regulations Restricted Materials Use Requirements, which may be lower than maximum label rates.

UC IPM Pest Management Guidelines: Potato
UC ANR Publication 3463


Resistance and tolerance of potato varieties to potato rot nematode (Ditylenchus destructor) and stem nematode (Ditylenchus dipsaci)

Julius Kühn‐Institut, Federal Research Centre for Cultivated Plants, Institute for National and International Plant Health, Braunschweig, Germany

Department for Crop Sciences, Section Agricultural Entomology, Georg‐August‐University Göttingen, Göttingen, Germany

P. Mwaura, Julius Kühn‐Institut, Federal Research Centre for Cultivated Plants, Institute for National and International Plant Health, Messeweg 11/12, 38104 Braunschweig, Germany. Email: [email protected]

Julius Kühn‐Institut, Federal Research Centre for Cultivated Plants, Institute for National and International Plant Health, Braunschweig, Germany

Department for Crop Sciences, Section Agricultural Entomology, Georg‐August‐University Göttingen, Göttingen, Germany

Julius Kühn‐Institut, Federal Research Centre for Cultivated Plants, Institute for National and International Plant Health, Braunschweig, Germany

Department for Crop Sciences, Section Agricultural Entomology, Georg‐August‐University Göttingen, Göttingen, Germany

P. Mwaura, Julius Kühn‐Institut, Federal Research Centre for Cultivated Plants, Institute for National and International Plant Health, Messeweg 11/12, 38104 Braunschweig, Germany. Email: [email protected]

Julius Kühn‐Institut, Federal Research Centre for Cultivated Plants, Institute for National and International Plant Health, Braunschweig, Germany

Department for Crop Sciences, Section Agricultural Entomology, Georg‐August‐University Göttingen, Göttingen, Germany


Ditylenchus destructor and Ditylenchus dipsaci are economically important plant‐parasitic nematodes, affecting potato production mostly in temperate climates. Management through crop rotation is not feasible because of their wide host range. These nematodes are listed as quarantine pests in many countries. Limited information exists on the resistance and tolerance of currently cultivated potatoes to D. destructor and D. dipsaci. Two greenhouse experiments were conducted to screen 25 potato varieties for resistance to and tolerance for D. destructor and D. dipsaci infections. Reproduction factor (RF) and relative susceptibility (RS) were used to evaluate resistance, while potato tuber damage and tuber weight reduction was used to evaluate tolerance. Based on the RF, 16 varieties were evaluated as susceptible (S) while 5 varieties were evaluated as resistant (R) to D. destructor; varieties ‘Innovator’, ‘Aveka’ and ‘Spunta’ were resistant to D. dipsaci based on RF. ‘Désirée’ was observed to be highly susceptible to D. destructor and D. dipsaci in both experiments and was used as the standard susceptible control variety for the calculation of RS. A scale of 1–9 was used to classify RS of the potato varieties to D. destructor and D. dipsaci, where 9 indicated the highest level of resistance. All classes of resistance to D. destructor and D. dipsaci were observed in the potato varieties tested in the experiments. Six varieties had significantly lower RS to D. dipsaci than the standard susceptible control variety. Tolerant to highly sensitive potato varieties to both nematodes were also observed. RS and external potato tuber damage were identified as suitable methods for resistance and tolerance determination, respectively. This study provides essential information on the status of resistance and tolerance in potato varieties against D. destructor and D. dipsaci but needs to be confirmed under field conditions.


Potato Cyst Nematodes threaten crop in Kenya

A young farmer inspect his potato plantation in Eldama Ravine, Baringo. Potato Cyst Nematode (PCN), a deadly pest currently ravages potato crops in several counties in Kenya (Courtesy: Daily Nation)

Infestation of potatoes by the Potato Cyst Nematode (PCN), a pest ravaging potato plants that was discovered in Kenya two years ago, has reached alarming levels.

A survey done in 20 counties through support from United Nations Food and Agricultural Organisation (FAO), whose results were released two weeks ago, shows that PCN infestation has reached 80 per cent to 100 per cent in some of the potato growing areas.

The study shows that the future of potato production is bleak unless the government takes emergency measures to stem the rapid spread of the devastating pest.

PCN (Globodera rostociensis or Globodera pallida) is classified as a quarantine pest by FAO, meaning that in countries where it is detected, tough restrictions are imposed.

This include ban on potato production and transport to other growing regions and even countries to stop spread. The pest can remain in the soil for up to 30 years.

Infested potatoes usually show early maturity, produce tiny tubers and are usually stunted. Up to now, there is no known chemical or biological agent that can control the pest.

Nyandarua leads with a prevalence rate of 91 per cent followed by Elgeyo Marakwet (87 per cent), Nakuru 88 per cent and Narok (88 per cent).

Other counties with high infestation levels are Trans-Nzoia (100 percent), West Pokot (100 percent) and Taita Taveta (100 percent).

However, the three are not major potato producers. Of the 1,200 potato growing farms sampled in the survey, only four that produce seeds were found to be free of the pest.

Importation of whole potato tubers into the country has been blamed for the introduction of the pest. The Kenya Plant Health Inspectorate Service (Kephis) is supposed to ensure that any potato seed brought in has to be in form of in-vitro plantlets that are quarantined at its station in Muguga and tested for pests and diseases before being put in experimentation plot for trials and eventual release as seeds as stipulated under the Seed and Plant Varieties Act Cap 325.

However, the Ministry of Agriculture has at times gone around this requirement and allowed imports of potatoes from Netherlands and other European countries into citing potato seed shortage.

An important Crop

The government can only produce about 1 per cent of potato seed required while 99 per cent used by farmers is uncertified, which has been blamed for the rapid spread of diseases and pests such as PCN.

The survey has established that all government seed production units run by Kenya Agriculture and Livestock Research Institute are infested with PCN.

This includes seed multiplication sites in the Agricultural Development Corporation farms. This means that the government cannot be able to produce any seed in future unless new seed production areas that are not affected by the pest are identified.

Deputy Director in-charge of Phytosanitary Services at Kephis Dr Issac Wachira said the body had overlooked the inspection of PCN in all planting material coming into the country because it was mainly prevalent in Europe and other temperate countries.

He said going forward, strict inspection of all plant material both for export and imports will be enforced to protect the country from re-infestation.

Dr Issac Wachira, Deputy Director in-charge of Phytosanitary Services at Kephis:

“We had put our attention so much on potato diseases such as bacterial wilt in seed potatoes in our inspection work because we did not know that PCN was already in Kenya.”

“From now on, we will enforce strict inspections of all material coming into the country to ensure the pest is contained.”

“We are aware that infested potted plants, packaging material, flower bulbs and even farm implements can transfer the pest from one region to another.”

The Head of the Crops Unit at FAO (Kenya) Dr Wilson Rono asked all stakeholders in the potato industry to use the results of the survey to come up with a common strategy to combat the pest to stop its spread and restore potato production in the country to its former status for food security.

Potato is the second most important crop in the country after maize.

It is grown by more than 800,000 farmers generating more than Sh50 billion to the country.

The survey was conducted by ICIPE in collaboration with Kalro, Kephis, Kenyatta University, the International Institute of tropical agriculture (IITA) and the Ministry of Agriculture Livestock and Fisheries.


Root Knot Nematode Disease: A Stunted Plant Growth Cause

A root knot nematode infestation is probably one of the least talked about but very damaging pests in the gardening landscape. These microscopic worms can move into your soil and attack your plants, leaving them with stunted plant growth and eventual death.

What is a Root Knot Nematode?

A root knot nematode is a parasitic, microscopic worm that invades the soil and the roots of the plants in the soil. There are several varieties of this pest but all of the varieties have the same effect on plants.

Root Knot Nematode Symptoms

Root knot nematode can be spotted initially by stunted plant growth and a yellow color to the plant. To confirm the presence of this parasite, you can look at the roots of the affected plant. True to its name, this nematode will cause root knots or bumps to appear on the roots of most plants. They may also cause the root system to become deformed or harry.

The root knots and deformations prevent the plant from being to take up water and nutrients from the soil through its roots. This results in the stunted plant growth.

Root Knot Nematode Control

Once root knot nematodes have invaded the soil, it can be difficult to get rid of them since they attack a wide variety of plants, including common weeds such as purslane and dandelion.

One course of action is to use non-host plants in the location that the root knot nematodes have infested. Corn, clover, wheat and rye are all resistant to this pest.

If crop rotation is not possible, the soil should be solarized followed by a year of being fallow. The solarization will eliminate the majority of the worms and the year of being fallow will ensure that the remaining pests have no where to lay their eggs.

Of course, the best control of this pest is to ensure that it never enters your garden in the first place. Only use plants that come from trusted, uninfected sources.

If you suspect that your garden has been infested with this pest, bring a soil sample to your local extension office and specifically ask them to test for the pest. Root knot nematode is a quickly growing menace that is not always on the radar of local offices and is not routinely tested for unless requested.


What kind of pest is a stem potato nematode?

Nematode syn. Eelworm Control © Frances Michaels

Nematodes are not insects but microscopic, long, thin worms, which is why a common name for them is eelworms. This soil-borne pest causes stunted, unproductive plants. A common way to identify the problem is infected plants will wilt rapidly in hot weather. When nematodes burrow into the roots they stimulate the development of galls on the roots which become swollen, disfigured and knotty. Root knot nematodes infest a wide range of plants, including roses, potatoes, carrots, tomatoes, cucumbers, lettuces and zucchini. The potato cyst nematode Globodera rostochiensis is very persistent in soils but luckily it is confined to a very small area of Victoria; this area has been quarantined to prevent further spread.

Suggested Organic Strategies

  • A healthy soil will have a range of microorganisms that are predators or parasites of nematodes. All the usual ways of building a healthy soil such as adding adding compost, mulching and green manuring will improve nematode control. More information on soil improvement.
  • A green manure can be grown specifically for nematode control as there are plants that when chopped through the soil will decompose and release a nematode killing gas; this process is known as bio-fumigation. Plants that contain high levels of bio-fumigant compounds include: rapeseed (canola) Brassica napus, BQ Mulch, marigolds and Indian mustard. BQ Mulch, canola and mustard are cool season crops. Marigold is a warm season crop that when mixed with cowpea makes an effective, warm season, nematode-controlling green manure.
  • Practising crop rotation helps as when a non-host crop is grown for a season it can starve the existing nematodes. Non-host plants include cowpea, soybean, oats, wheat and woolly pod vetch. A rotation of 2 years or more between susceptible crops is needed to control a serious outbreak. Vegetable crops resistant to nematodes include broccoli, corn, brussels sprouts, chives and leeks.
  • Good hygiene will help limit the spread of this pest as nematodes cannot move quickly through the garden, instead they are often spread on infected plants, muddy boots and garden tools.
  • When harvesting infected plants, remove as much infected root from the soil as possible and dispose of well away from garden areas. The infected roots can be used as mulch under native shrubs or trees but do not place them in a compost heap, as it is unlikely to get hot enough to kill the nematodes.
  • Solarisation can be a useful remedy for nematodes; it can also help combat stubborn weeds. To be effective do this in summer and first water the soil well. Then cover the soil with clear 4mm thick plastic. Stretch the plastic over the area, get it as close to the soil as possible. Bury the edges by digging a narrow trench, tucking the plastic in and back-filling. The aim is to raise the temperature to between 45°C and 50°C in the top 10 cm of soil. This is high enough to kill disease pathogens but most beneficial soil organisms will survive. Leave the plastic in place for 4 to 6 weeks and then plant as usual.
  • Digging fresh chicken manure into a hot, dry soil, something normally to be avoided, has been shown to reduce nematode numbers.
  • Drenching with water and molasses or sugar can also kill nematodes, but will have a negative impact on soil life.

Not all nematodes are a problem, a range of beneficial nematodes known as ‘entomopathogenic’ are used to control plant pests.


Tomato Pests and Diseases, Symptoms, Control

Tomato Pests and Diseases:

The following information is about Tomato Pests and Diseases that affect the Tomato crop yield.

Tomatoes are one of the most cultivated crops, Tomato crops can be easily grown under proper conditions and regular maintenance. Tomato crops can host of production problems and pathogens when conditions and maintenance are not ideal.

This article gives you the information that helps you to grow better tomatoes. Basically, your geographic location, environmental conditions, and cultural methods will affect disease and pest pressures.

A healthy tomato crop.

Foliar Diseases in Tomato crop:

The Main factors that spread the foliar diseases are High humidity, elevated temperatures, and lack of adequate air circulation. The main prevention step is to provide with adequate air flow: do not crowd plants; constant pruning; good ventilation.

Common foliar diseases in Tomato crop
  • Bacterial speck: Bacterial speck is a foliar disease that mainly affects the fruit, whether green or ripe. The affected leaves have minuscule dark spots; on green fruit, dark spots; and on ripe fruit, sunken dark spots. This disease can reduce the yields of plants and make fruits unpalatable/unmarketable. To prevent this disease, select varieties that are disease resistant to bacterial speck race 0, race 1.
  • Gray leaf spot: Gray Leaf Spot on tomato leaf is the sign of gray leaf spot disease, the development of small, dark-colored lesions on the leaves. These diseases will reduce productivity and eventual leaf drop. There are very limited high-quality commercial tomato varieties with grey leaf spot resistance as there are with other resistances.
  • Early blight: It is also called Alternaria leaf blight, early blight is a widespread disease, older and leaves are the initial site of infection. The lesions turn small, dark, irregularly shaped spots that increase gradually to concentric rings. This disease can cause leaf death and reduced yields. This infection often begins in the lower portion of the plant, it can extend into the upper leaves, and stems and fruits can be infected at any stage. Select tomato varieties which are resistant to early blight, and even in these varieties, resistance does not confer complete immunity from the disease, but the resistant plants are able to delay and minimize disease symptoms and sustain production.
  • Late blight: Late blight is a nickel-sized, wet or greasy-looking, grayish-black or brown spots on leaves, and white, fuzzy fungal growth on the underside of leaves. The fruit is also infected, resulting in dark-colored lesions that are hard and sunken. Late blight spreads rapidly and can be very destructive. The different races and disease-resistance genes can prevent disease.
  • Leaf mold: It is the most common tomato crop disease. Mainly affects due to high humidity and low air circulation. The upper- and undersides of the affected leaves with yellow will turn, irregularly-shaped spots on the upper-side and fuzzy olive-green, gray, or tannish-brown splotches on the underside. Leaf mold resistant varieties of tomatoes are common in varieties bred for greenhouse production.
  • Powdery mildew: The reason for powdery mildew on tomato crop is due to warm, dry climates. The signs of infection are circular collections of powdery-white pustules that sometimes coalesce on the upper side of the leaves. The leaves infected with powdery mildew eventually die as the infection spreads. There are very fewer varieties of commercial crops with PM resistance, and so far, the level of resistance is intermediate at best.

Tomato Crop.

Soilborne Disease of Tomato Crop

Soil-borne diseases in regions where tomatoes are grown as repeated crops. Crop rotation with non-solanaceous crops and grafting to disease-resistant rootstocks will reduce the occurrence and impact of soilborne diseases.

  • Bacterial wilt: The leaf wilt is mainly causing at high temperatures, but can be recovered during cool, nighttime temperatures. When the disease advances, extreme wilting and desiccation leads to plant death. This can be prevented by selecting bacterial wilt resistance varieties or using grafted plants with disease-resistant rootstocks.
  • Corky root rot: Mainly attacks the cool-temperature plantings, larger roots will take a corky texture, while smaller roots may rot and decay. The plants infected with corky root rot are often smaller and less vigorous. Growing the plants grafted to resistant rootstock is the best method to control corky root rot.
  • Fusarium crown and root rot: The Fusarium crown and root will affect the roots of young plants by entering through wounds and natural openings. The plant show signs by leaf yellowing and loses lower leaves. As the disease progresses, it leads to root rot, leaf wilting, and eventual plant death. Many FOR-resistant varieties are available, and most rootstocks are highly resistant to this disease.
  • Fusarium wilt: Fusarium wilt interrupts the flow of nutrients and water in a plant’s vascular system, which leads to yellowing and eventual leaf drop. Modern hybrid tomatoes and tomato rootstocks are resistant to Fusarium wilt.
  • Verticillium wilt: This fungalenters through small abrasions or lesions that can occur on the root surface. It interrupts the flow of nutrients and water within a plant’s vascular system, that leads to wilting and yellowing of the lower leaves. The leaves may show V-shaped lesion that can enlarge and eventually cause leaf death. Modern hybrid tomatoes and tomato rootstocks are resistant to Verticillium Wilt.

Seedborne Diseases in Tomato Crop

Seedborne diseases in tomatoes are controlled by seed treatment practices. Growers can control these diseases by purchasing seeds from a reputable dealer.

  • Bacterial canker: This is a common and destructive disease, mainly for greenhouse cultivators. The seedling infected will develop white leaf spots and show wilting, often leading to plant death. And the mature plants show symptoms on the leaves, fruit, and stems. This disease can be managed with preventive seed treatment practices.
  • Bacterial spot: Signs of bacterial leaf spot are small, irregular brown spots on the upper side of the leaves. As it progresses, the leaves turn yellow and shed, exposing the fruits to the possibility of sunscald. Sunscald can cause large lesions may also develop on the fruit. This disease can be managed with preventive seed treatment practices.

Stem Diseases in Tomato Crop

Alternaria stem canker: This disease affects not only the stems but also the leaves and fruits. The dark-brown to black cankers form on tomato plant stems, this cause most damage to the plant. As the cankers grow, they encircle the stem, causing the plant to die.

To reduce the spread of disease use drip irrigation rather than overhead watering. Treatment the affected plants with fungicides, which may not reduce the disease, but can help to slow the spreading.

Damping off: This is a most common seedling disease affects the young seedlings at the base of the stem, near the soil line. The affected stems appear weak, withered, or pinched. Low irrigation, cool conditions become more prevalent for this disease. Preventive control measures for damping off are using sterilized or composted soil mixes, avoiding overwatering, ensuring good air flow, and spraying trays with a light copper solution after sowing.

Pests in Tomato Crop:


These are green caterpillars that feed on the leaves and matured hornworms feed on fruit. This can show great impact in reducing productivity and yield. There are two types hornworms that attack tomatoes, tobacco hornworm and the tomato hornworm. These two hornworms are very similar in appearance. These can be controlled by handpicking the caterpillars off the leaves and destroying them or using some organic insecticide.


These pests feed on the fruit and leaves of tomatoes and carry diseases. They lay eggs on the underside of the leaves. The whiteflies can cause irregular ripening disorder in tomatoes.

Preventive measures are, encouraging of natural enemies, proper sanitation, and crop rotations with nonhost species, together with insecticides, such as horticultural oils, insecticidal soaps will show to have some limited effect. Using silver- or aluminum-colored mulch can help to control whiteflies.


The thrips can cause tomato spotted wilt virus. The thrips can be prevented by rotating crops and planting tomatoes away from where other host plants.


Aphids can be controlled by some natural parasitic and predatory enemies, and, as with whiteflies, repelled by the placement of reflective mulches early in the season.

Tomato/potato psyllid:

This pest feeds on the underside of leaves and injects some toxins to the leaves that induce chlorosis and stunting of the plant’s growth tips, a condition known as psyllid yellows. These pests can lead to severe wilting and stem death.

Nematode Pests in Tomato Crop:

Root-knot nematode:

This mainly infects the roots of the plants. The affected roots are less effective at taking up nutrients and water. Which makes plants stunted, less vigorous, and produce lower yields. All the modern hybrid tomato varieties are resistant to root-knot nematode.

Pest and Diseases Prevention Basics

When growing tomato crops, following are the preventive measures:

  • Make a deep study about pest and disease pressures are common in your area and select resistant varieties.
  • Select varieties that are suitable or specific growing environment (field, greenhouse, high tunnel, hydroponic system).
  • Use best cultural practices: practice crop rotation; good hygiene, remove the crop debris in every season; and proper care, neither overwatering nor underwatering, to create an environment favorable to plant growth, rather than conditions that set the stage for problems.

Bottom Line: If you are a tomato farmer and growing tomatoes commercially, you must take care of tomato pests and diseases for healthy plant growth, quality fruits, and higher yields.


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