|Monitoring and sampling
Monitoring or assessment of nematode populations is an important aid to nematode management. Monitoring should begin well before problems occur, as it is too late to prevent crop losses once root-knot nematode damage is seen in the field.
Assessment of galling in the field
When tomatoes (or other root-knot susceptible crops) are planted in the same field every year, a check for root-knot galls at the end of the season provides valuable information on the level of nematode infestation and the likelihood of nematode damage in the next year. A thorough sampling of the field at harvest may provide as much information as having soil samples analysed for nematodes before the planting of the next crop.
Dig up plants from several areas of the field, taking care to retrieve the fine feeder roots, and look carefully for the presence of galls. The number and size of the galls provides an indication of the degree of root-knot nematode infestation.
Soil samples can be collected before planting and sent to a laboratory for extraction, identification and a count of the nematodes present. Divide fields into blocks no larger than about 4 ha to sample areas of similar soil type or cropping history separately. For each block, collect about 50 small subsamples of soil with a shovel or sampling tube at depths of 5-20 cm and place in a bucket. Mix thoroughly, remove a 500 mL subsample, seal in a plastic bag and send to the laboratory for analysis.
Do not leave samples in the sun or refrigerate them. The best storage temperatures are 10 15 o C. Include your name, address, date, location of the field, cropping history, the variety being planted and any information on previous nematicide use or nematode symptoms observed.
Instead of sending soil samples to a laboratory for nematode analysis, a simple bioassay is sometimes useful, particularly for detecting low populations of root-knot nematode. Transplant a nematode-free tomato seedling of a susceptible variety into a pot containing about 2 L of your soil sample. Grow plants at temperatures of 20-28 o C for about one month, and then remove the root system and examine it for galls. At this stage, the galls (if present) will be less than 0.5 mm in diameter but their occurrence will indicate the presence of root-knot nematode.
The bioassay method has an advantage over nematode extraction methods because larger samples can be processed. Growing the plants for one month allows ample time for eggs to hatch, and these nematodes to invade the plant and be detected. Its main disadvantage is that samples must be collected at least two months before planting.
Interpretation of results of monitoring data
Nematode analysis is likely to show a number of plant-parasitic species. However, root-knot nematode is the only species known to cause economic damage to tomatoes in Queensland and nematode management decisions should be made on the basis of its presence or absence.
Unfortunately, not all nematodes are recovered with the extraction methods currently available and this applies particularly to nematodes in the egg stage. When relatively small samples are processed, some nematodes may be missed when population levels are low. The absence of root-knot nematode in these extractions does not necessarily mean that the nematode is not present in the field. In this case, use information about the soil texture, previous cropping history and previous occurrence of nematode damage to decide whether the negative result is accepted or whether the block should be re-sampled.
Tomatoes are very susceptible to root-knot nematodes under Queensland conditions. In the past, control measures were normally recommended if one root-knot nematode was found in a 200 mL soil sample taken before planting or a gall was found in the roots of bioassay plants. However, recent research suggests that the economic threshold may be a little higher than previously thought. Thus, well managed crops grown in fields with a preplant density of 1-10 root-knot nematodes per 200 mL soil may be heavily galled at harvest but will suffer little yield loss from nematodes.
Root-knot problems increase and control becomes more difficult when tomatoes or other susceptible crops are grown without rotation.
However, crop rotation will not eliminate infestations because root-knot nematodes can remain in the soil as eggs for at least a year between host crops and most species can feed on a wide range of weeds. Nonetheless, rotation can significantly reduce losses when a field is planted again to a susceptible crop.
Winter cereals are useful because they are generally poor hosts and little nematode reproduction occurs during the cold winter months. It is more difficult to find summer crops with good resistance to root-knot nematode, though sorghum x Sudan grass hybrids (particularly cv. Jumbo) are useful against most populations of the nematode.
Fallow and cultivation
Repeated cultivation kills nematodes in the upper soil layers by exposing them to mechanical abrasion, and the heating and drying action of the sun. If the field is maintained weed free, nematodes also die of starvation. In warm, moist soils in Queensland, a 4-6 month fallow may reduce root-knot nematode populations by more that 95 per cent. Longer fallow periods are not normally economically feasible and they increase the risk of soil erosion.
As nematode populations have the capacity to increase rapidly, plough out plants as soon as the crop is harvested to prevent further multiplication. At this time, most of the nematode population is in the roots rather than the soil. Therefore, if these roots are removed from the field and destroyed (e.g. by burning), the nematode population immediately and substantially reduces.
Tomato varieties with nematode resistance are available but not always commercially acceptable because of poor agronomic characteristics. Experimental breeding lines with nematode resistance are being tested and may be more suitable. These varieties provide adequate but not absolute protection against common populations of M. incognita and M. javanica. M. hapla and some races of M. incognita are sometimes capable of attacking resistant varieties.
Seedbeds — In crops established from seedlings, transplants must be free of root-knot nematodes. Before planting, fumigate all seedbeds with a registered chemical according to label directions.
Potting mixes — If peat, sand and other components are obtained from sources free of root-knot nematode and are not contaminated before use, the treatment of potting mixes for nematode control is unnecessary. Treatments for damping-off fungi (e.g. aerated steam at 60°C for 30 minutes) will also kill nematodes.
Field — If the management practices above are adopted, nematicides should only be needed in the field as a last resort (e.g. in sandy soils where tomatoes are particularly prone to nematode damage). Even in situations where root-knot nematode problems are usually severe, the use of good management practices reduces the nematode population pressure and gives nematicides a greater chance of providing effective control.
The following information is a suggested decision-making timetable that will assist your management of nematodes in tomatoes.
If you are growing a crop susceptible to root-knot, check a sample of roots and determine the level of galling approximately 12 months before planting tomatoes. Eight months before planting, destroy nematode-infested root systems and plough out the crop immediately after harvest. Maintain a weed-free fallow until a cover crop is planted. Plant a cover crop that is not susceptible to root-knot nematodes, such as winter cereals or forage sorghum. Two months before planting, collect soil samples and either do a bioassay or test the soil for nematodes. If the results of nematode analyses or bioassays, or the previous occurrence of nematode problems, suggest that nematodes are likely to cause damage, either plant a nematode-resistant variety or apply a preplant nematicide.
Chemical registrations and permits
Check the Australian Pesticides and Veterinary Medicines Authority’s chemical database and permit database for chemicals registered or approved under permit to treat this pest on the target crop in your state or location. Always read the label and observe withholding periods.
Roundworms (Nematode Infection) Types, Symptoms, Treatment
There are many different types of parasitic worms that can infect humans. Roundworms are one such type. There are some 500,000 species of roundworms and about 60 are known to infect humans. It can infect a number of different organs in the human body, not only the digestive tract as is often though. Most infections are not serious and a person may not even be aware of the worms. But some roundworm infections can be serious or even complicate into life-threatening conditions.
What are roundworms?
Roundworms are parasitic worms (helminths) that belong to the phylum Nematoda. In other words, roundworms is the common name for one type of parasitic worm known as nematodes. These worms are elongated, have a large body cavity and an intestinal system. Most roundworms that parasitize humans live in the gut. It is estimated to affect as much as one-third of the world’s population although the majority of people have no major symptoms and are therefore unaware of the worm infection.
Are roundworms deadly?
Some roundworms can cause fatal complications in humans. It is more likely to occur if the roundworms move outside of the intestines to other vital organs. It may then lead to inflammatory responses within these vital organs. However, life threatening complications are rare in most people who contract roundworms. Newborns and people with a weakened immune system (immunocompromised) are at a much greater risk of death from the complications of roundworm infections.
Picture of hookworms
Spread of Roundworms
There are several ways that roundworms enter the human body. It can be spread from an infected person to another person who is uninfected. The main routes by which roundworms enter include:
- Consuming food and water that is contaminated with feces containing worm eggs.
- Insects that bite humans and pass the immature worms in its saliva into the body.
- Penetrating human skin to gain entry into the bloodstream.
These routes are not only applicable to humans. Many roundworms that infect humans can also infect other mammals. Some worms can be spread from person to person, while others require soil or insects to complete a part of its life cycle in order to infect people.
Types of Roundworms
There are a number of different species of roundworms but the most common ones to infect humans include:
- Ascaris lumbricoides (most common roundworm infections in humans)
- Hookworms (Ancylostoma duodenale and Necator americanus)
- Guinea worm (Dracunculus medinensis)
- Filarial nematodes (roundworms) of which eight are known to parasitize humans. These eight worms can be divided into 3 categories:
– Lymphatic filariasis – Wuchereria bancrofti, Brugia malayi, and Brugia timori.
– Cutaneous filariasis – Loa loa (the African eye worm), Mansonella streptocerca and Onchocerca volvulus.
– Body cavity filariasis – Mansonella perstans and Mansonella ozzardi.
- Pinworm (Enterobius vermicularis)
- Whipworm (Trichuris trichiura)
- Trichinella worms (T. spiralis, T. pseudospiralis, T. nativa, T. murelli, T. nelsoni, T. britovi, T. papuae)
- Angiostrongylus worms (A. cantonensis and A. costaricensis)
- Strongyloide worms (mainly Strongyloides stercoralis and less often S. fülleborni)
- Toxocara worms (Toxocara canis and Toxocara cati)
- Gnathostoma worms (Gnathostoma spinigerum and Gnathostoma hispidum)
- Anisakis (Anisakis simplex or Pseudoterranova decipiens)
Diseases due to infection with these worms are named according to the worms that cause it, such as:
- Ascariasis caused by Ascaris lumbricoides.
- Dracunculiasis caused by guinea worms.
- Filariasis caused by filarial nematodes.
- Strongyloidiasis caused by strongyloide worms.
The nature of the diseases caused by roundworms are somewhat similar. Most parasitic worms do not replicate within the human host. Instead the eggs pass out of the human body until it hatches and matures partly before infecting another person, or these eggs have to be consumed. Therefore there usually has to be repeated exposure to adult worms, its larvae or eggs in order for it to be sufficient to cause disease within humans.
The human immune system does not have the same immune protection against roundworms as it does to other microbes like bacteria or protozoa. Since Ascaris lumbricoides which causes ascariasis is the most common of these worms to infect humans, it is worth focusing on it specifically. Most roundworms infections will be similar but there are some distinct and significantly varying disease processes with some of these worms.
Picture of the adult female Ascariasis lumbricoides worm
In ascariaisis, the worm eggs are consumed. It then hatches in the small intestine and larvae emerge. These larvae penetrate the intestinal wall and migrate to the large veins of the liver. From here it moves to the lungs. The larvae are expectorated and swallowed again. It then goes to the middle portion of the small intestine (jejunum) where it matures into adult worms. These adult worms are then able to sustain themselves by feeding on nutrients in the gut. Eventually adult worms release eggs which are passed out in the feces. It can then contaminate food or water and the cycle is repeated.
Signs and Symptoms
The signs and symptoms largely depend on the number of worms in the body, and the location of these worms. Gastrointestinal symptoms are the most common. However, it is important to note that most people who do have roundworm infection are not even aware about it.
- Digestive tract (gut) symptoms may include:
– Abdominal pain
– Nausea and/or vomiting
– Bowel movements with visible worms
– Blood in the stool
- Lung symptoms include:
– Difficulty breathing
- Generalized symptoms include:
– Weight loss
– Malaise (feeling unwell)
– Fever- Fatigue
– Failure to grow
Depending on the worm there may be skin, nerve and eye symptoms. It can be mild or as serious as loss of vision as may be seen in river blindness (onchocerciasis which is caused by the filarial worm Onchocerca volvulus). Bowel obstruction may occur in some instances when the worms increase in number in the intestine and become tangled. Some worms attempt to exit through the nose in much the same way as some worms pass out in the stool.
Diagnosis and Treatment
A roundworm infection diagnosis first needs to be confirmed before medication can be prescribed.
Tests and Scans
This can be done with diagnostic investigations like a stool tests. The eggs of the worm may be found in the stool, and sometimes even the adult roundworm. The larvae may also be found in the sputum. Blood tests may reveal the body’s response to a large number of worms like raised immune activity and an increase in certain white blood cells. However, blood test alone cannot identify a roundworm infection or the type of worm. Sometimes the worms may be visible on an x-ray or ultrasound. A biopsy of skin lesions may be done to confirm the diagnosis in onchocerciasis.
Roundworm infection can be effectively treated. However, the focus should also be on prevention to avoid a recurrence of the infection. The worms do not have to be removed surgically unless large number of worms are causing an obstruction, or other complications. Medication is usually effective in eradicating the worm. The correct drugs can also prevent complications. Some of these drugs include:
- Mebendazole and albendazole which are effective against most roundworms that infect humans.
- Prednisone for severe toxocariasis.
The fight against strawberry nematode folk methods
Discover more about DNA, genes and genomes, and the implications for our health and society.
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This 3D animation shows you how DNA is copied in a cell. It shows how both strands of the DNA helix are unzipped and copied to produce two identical DNA molecules.
A genome is an organism’s complete set of genetic instructions. Each genome contains all of the information needed to build that organism and allow it to grow and develop.
All living things have DNA. This hands-on activity will enable you to extract DNA from fruit, such as strawberries, using everyday household items.
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This film shows all of the processes involved in sequencing a DNA sample; from receiving a sample DNA to releasing the assembled DNA sequence data.
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The fight against strawberry nematode folk methods
(Rhabditida: Steinernematidae & Heterorhabditidae)
By David I. Shapiro-Ilan, USDA-ARS, SEFTNRL, Byron, GA &
Randy Gaugler, Department of Entomology, Rutgers University, New Brunswick New Jersey
Nematodes are simple roundworms. Colorless, unsegmented, and lacking appendages, nematodes may be free-living, predaceous, or parasitic. Many of the parasitic species cause important diseases of plants, animals, and humans. Other species are beneficial in attacking insect pests, mostly sterilizing or otherwise debilitating their hosts. A very few cause insect death but these species tend to be difficult (e.g., tetradomatids) or expensive (e.g. mermithids) to mass produce, have narrow host specificity against pests of minor economic importance, possess modest virulence (e.g., sphaeruliids) or are otherwise poorly suited to exploit for pest control purposes. The only insect-parasitic nematodes possessing an optimal balance of biological control attributes are entomopathogenic or insecticidal nematodes in the genera Steinernema and Heterorhabditis. These multi-cellular metazoans occupy a biocontrol middle ground between microbial pathogens and predators/parasitoids, and are invariably lumped with pathogens, presumably because of their symbiotic relationship with bacteria.
Entomopathogenic nematodes are extraordinarily lethal to many important insect pests, yet are safe for plants and animals. This high degree of safety means that unlike chemicals, or even Bacillus thuringiensis, nematode applications do not require masks or other safety equipment; and re-entry time, residues, groundwater contamination, chemical trespass, and pollinators are not issues. Most biologicals require days or weeks to kill, yet nematodes, working with their symbiotic bacteria, can kill insects within 24-48 hours. Dozens of different insect pests are susceptible to infection, yet no adverse effects have been shown against beneficial insects or other nontargets in field studies (Georgis et al., 1991; Akhurst and Smith, 2002). Nematodes are amenable to mass production and do not require specialized application equipment as they are compatible with standard agrochemical equipment, including various sprayers (e.g., backpack, pressurized, mist, electrostatic, fan, and aerial) and irrigation systems.
Hundreds of researchers representing more than forty countries are working to develop nematodes as biological insecticides. Nematodes have been marketed on every continent except Antarctica for control of insect pests in high-value horticulture, agriculture, and home and garden niche markets.
Steinernematids and heterorhabditids have similar life histories. The non-feeding, developmentally arrested infective juvenile seeks out insect hosts and initiates infections. When a host has been located, the nematodes penetrate into the insect body cavity, usually via natural body openings (mouth, anus, spiracles) or areas of thin cuticle. Once in the body cavity, a symbiotic bacterium (Xenorhabdus for steinernematids, Photorhabdus for heterorhabditids) is released from the nematode gut, which multiplies rapidly and causes rapid insect death. The nematodes feed upon the bacteria and liquefying host, and mature into adults. Steinernematid infective juveniles may become males or females, where as heterorhabditids develop into self-fertilizing hermaphrodites although subsequent generations within a host produce males and females as well.
The life cycle is completed in a few days, and hundreds of thousands of new infective juveniles emerge in search of fresh hosts. Thus, entomopathogenic nematodes are a nematode-bacterium complex. The nematode may appear as little more than a biological syringe for its bacterial partner, yet the relationship between these organisms is one of classic mutualism. Nematode growth and reproduction depend upon conditions established in the host cadaver by the bacterium. The bacterium further contributes anti-immune proteins to assist the nematode in overcoming host defenses, and anti-microbials that suppress colonization of the cadaver by competing secondary invaders. Conversely, the bacterium lacks invasive powers and is dependent upon the nematode to locate and penetrate suitable hosts.
Production and Storage Technology
Entomopathogenic nematodes are mass produced for use as biopesticides using in vivo or in vitro methods (Shapiro-Ilan and Gaugler 2002). In vivo production (culture in live insect hosts) requires a low level of technology, has low startup costs, and resulting nematode quality is generally high, yet cost efficiency is low. The approach can be considered ideal for small markets. In vivo production may be improved through innovations in mechanization and streamlining. A novel alternative approach to in vivo methodology is production and application of nematodes in infected host cadavers; the cadavers (with nematodes developing inside) are distributed directly to the target site and pest suppression is subsequently achieved by the infective juveniles that emerge. In vitro solid culture, i.e., growing the nematodes on crumbled polyurethane foam, offers an intermediate level of technology and costs. In vitro liquid culture is the most cost- efficient production method but requires the largest startup capital. Liquid culture may be improved through progress in media development, nematode recovery, and bioreactor design. A variety of formulations have been developed to facilitate nematode storage and application including activated charcoal, alginate and polyacrylamide gels, baits, clay, paste, peat, polyurethane sponge, vermiculite, and water-dispersible granules. Depending on the formulation and nematode species, successful storage under refrigeration ranges from one to seven months. Optimum storage temperature for formulated nematodes varies according to species; generally, steinernematids tend to store best at 4-8 °C whereas heterorhabditids persist better at 10-15 °C.
Relative Effectiveness and Application Parameters
Growers will not adopt biological agents that do not provide efficacy comparable with standard chemical insecticides. Technological advances in nematode production, formulation, quality control, application timing and delivery, and particularly in selecting optimal target habitats and target pests, have narrowed the efficacy gap between chemical and nematode agents. Nematodes have consequently demonstrated efficacy in a number of agricultural and horticultural market segments.
Entomopathogenic nematodes are remarkably versatile in being useful against many soil and cryptic insect pests in diverse cropping systems, yet are clearly underutilized. Like other biological control agents, nematodes are constrained by being living organisms that require specific conditions to be effective. Thus, desiccation or ultraviolet light rapidly inactivates insecticidal nematodes; chemical insecticides are less constrained. Similarly, nematodes are effective within a narrower temperature range (generally between 20 °C and 30 °C) than chemicals, and are more impacted by suboptimal soil type, thatch depth, and irrigation frequency (Georgis and Gaugler, 1991; Shapiro-Ilan et al., 2006). Nematode-based insecticides may be inactivated if stored in hot vehicles, cannot be left in spray tanks for long periods, and are incompatible with several agricultural chemicals. Chemicals also have problems (e.g., mammalian toxicity, resistance, groundwater pollution, etc.) but a large knowledge base has been developed to support their use. Accelerated implementation of nematodes into IPM systems will require users to be more knowledgeable about how to use them effectively.
Therefore, based on the nematodes’ biology, applications should be made in a manner that avoids direct sunlight, e.g., early morning or evening applications are often preferable. Soil in the treated area should be kept moist for at least two weeks after applications. Application to aboveground target areas is difficult due to the nematode’s sensitivity to desiccation and UV radiation; however, some success against certain above-ground targets has been achieved and recently approaches have been enhanced by improved formulations (e.g., Shapiro-Ilan et al., 2010). In all cases, the nematodes must be applied at a rate that is sufficient to kill the target pest; generally, 250,000 infective juveniles per m2 of treated area is required (though in some cases an increased or slightly decreased rate may be suitable) (Shapiro-Ilan et al., 2002). Additionally, it is important to match the appropriate nematode species to the particular pest that is being targeted (see the table below for species effectiveness).
Nematodes are formulated and applied as infective juveniles, the only free-living and therefore environmentally tolerant stage. Infective juveniles range from 0.4 to 1.5 mm in length and can be observed with a hand lens or microscope after separation from formulation materials. Disturbed nematodes move actively, however sedentary ambusher species (e.g. Steinernema carpocapsae, S. scapterisci) in water soon revert to a characteristic «J»-shaped resting position. Low temperature or oxygen levels will inhibit movement of even active cruiser species (e.g., S. glaseri, Heterorhabditis bacteriophora). In short, lack of movement is not always a sign of mortality; nematodes may have to be stimulated (e.g., probes, acetic acid, gentle heat) to move before assessing viability. Good quality nematodes tend to possess high lipid levels that provide a dense appearance, whereas nearly transparent nematodes are often active but possess low powers of infection.
Insects killed by most steinernematid nematodes become brown or tan, whereas insects killed by heterorhabditids become red and the tissues assume a gummy consistency. A dim luminescence given off by insects freshly killed by heterorhabditids is a foolproof diagnostic for this genus (the symbiotic bacteria provide the luminescence). Black cadavers with associated putrefaction indicate that the host was not killed by entomopathogenic species. Nematodes found within such cadavers tend to be free-living soil saprophages.
Steinernematid and heterorhabditid nematodes are exclusively soil organisms. They are ubiquitous, having been isolated from every inhabited continent from a wide range of ecologically diverse soil habitats including cultivated fields, forests, grasslands, deserts, and even ocean beaches. When surveyed, entomopathogenic nematodes are recovered from 2% to 45% of sites sampled (Hominick, 2002).
Because the symbiotic bacterium kills insects so quickly, there is no intimate host-parasite relationship as is characteristic for other insect-parasitic nematodes. Consequently, entomopathogenic nematodes are lethal to an extraordinarily broad range of insect pests in the laboratory. Field host range is considerably more restricted, with some species being quite narrow in host specificity. Nonetheless, when considered as a group of nearly 80 species, entomopathogenic nematodes are useful against a large number of insect pests (Grewal et al., 2005). Additionally, entomopathogenic nematodes have been marketed for control of certain plant parasitic nematodes, though efficacy has been variable depending on species (Lewis and Grewal, 2005). A list of many of the insect pests that are commercially targeted with entomopathogenic nematodes is provided in the table below. As field research progresses and improved insect-nematode matches are made, this list is certain to expand.
USE OF NEMATODES AS BIOLOGICAL INSECTICIDES
|Artichoke plume moth
||Sc, Sf, Sr
|Banana root borer
||Sc, Sf, Sg
||Sphenophorus spp. (Coleoptera: Curculionidae)
|Black vine weevil
||Hb, Hd, Hm, Hmeg, Sc, Sg
||Synanthedon spp. and other sesiids
||Fruit trees & ornamentals
||Hb, Sc, Sf
||Home yard, turf
|Citrus root weevil
||Pachnaeus spp. (Coleoptera: Curculionidae
||Sc, Sf, Sr
|Diaprepes root weevil
|Grape root borer
|Large pine weevil
||Liriomyza spp. (Diptera: Agromyzidae)
||Sc, Sr, Scap
||Nut and fruit trees
||Hb, Sc, Sg, Ss, Hz
|Strawberry root weevil
|Small hive beetle
||Yes (Hi, Sr)
||Hb, Sc, Sf
* At least one scientific study reported 75% suppression of these pests using the nematodes indicated in field or greenhouse experiments. Subsequent/other studies may reveal other nematodes that are virulent to these pests. Nematodes species used are abbreviated as follows: Hb=Heterorhabditis bacteriophora, Hd = H. downesi, Hi = H. indica, Hm= H. marelata, Hmeg = H. megidis, Hz = H. zealandica, Sc=Steinernema carpocapsae, Sf=S. feltiae, Sg=S. glaseri, Sk = S. kushidai, Sr=S. riobrave, Sscap=S. scapterisci, Ss = S. scarabaei.
** Efficacy of various pest species within this group varies among nematode species.
Characteristics of Some Commercialized Species
Steinernema carpocapsae: This species is the most studied of all entomopathogenic nematodes. Important attributes include ease of mass production and ability to formulate in a partially desiccated state that provides several months of room-temperature shelf-life. S. carpocapsae is particularly effective against lepidopterous larvae, including various webworms, cutworms, armyworms, girdlers, some weevils, and wood-borers. This species is a classic sit-and-wait or «ambush» forager, standing on its tail in an upright position near the soil surface and attaching to passing hosts. Consequently, S. carpocapsae is especially effective when applied against highly mobile surface-adapted insects (though some below-ground insects are also controlled by this nematode). S. carpocapsae is also highly responsive to carbon dioxide once a host has been contacted, thus the spiracles are a key portal of host entry. It is most effective at temperatures ranging from 22 to 28°C.
Steinernema feltiae: S. feltiae is especially effective against immature dipterous insects, including mushroom flies, fungus gnats, and tipulids as well some lepidopterous larvae. This nematode is unique in maintaining infectivity at soil temperatures as low as 10°C. S. feltiae has an intermediate foraging strategy between the ambush and cruiser type.
Steinernema glaseri: One of the largest entomopathogenic nematode species at twice the length but eight times the volume of S. carpocapsae infective juveniles, S. glaseri is especially effective against coleopterous larvae, particularly scarabs. This species is a cruise forager, neither nictating nor attaching well to passing hosts, but highly mobile and responsive to long-range host volatiles. Thus, this nematode is best adapted to parasitize hosts possessing low mobility and residing within the soil profile. Field trials, particularly in Japan, have shown that S. glaseri can provide control of several scarab species. Large size, however, reduces yield, making this species significantly more expensive to produce than other species. A tendency to occasionally «lose» its bacterial symbiote is bothersome. Moreover, the highly active and robust infective juveniles are difficult to contain within formulations that rely on partial nematode dehydration. In short, additional technological advances are needed before this nematode is likely to see substantial use.
Steinernema kushidai: Only isolated so far from Japan and only known to parasitize scarab larvae, S. kushidai has been commercialized and marketed primarily in Asia.
Steinernema riobrave: This novel and highly pathogenic species was originally isolated from the Rio Grande Valley of Texas, but has since been also been isolated in other areas, e.g., in the southwestern USA. Its effective host range runs across multiple insect orders. This versatility is likely due in part to its ability to exploit aspects of both ambusher and cruiser means of finding hosts. Trials have demonstrated its effectiveness against corn earworm, mole crickets, and plum curculio. Steinernema riobrave has also been highly effective in suppressing citrus root weevils (e.g., Diaprepes abbreviates and Pachnaeus species). This nematode is active across a range of temperatures; it is effective at killing insects at soil temperatures above 35°C, and can also infect at 15 °C. Persistence is excellent even under semi-arid conditions, a feature no doubt enhanced by the uniquely high lipid levels found in infective juveniles. Its small size provides high yields whether using in vivo (up to 375,000 infective juveniles per wax moth larvae) or in vitro methods.
Steinernema scapterisci: The only entomopathogenic nematode to be used in a classical biological control program, S. scapterisci was isolated from Uruguay and first released in Florida in 1985 to suppress an introduced pest, mole crickets. The nematode become established and presently contributes to control. Steinernema scapterisci is highly specific to mole crickets. Its ambusher approach to finding insects is ideally suited to the turfgrass tunneling habits of its host. Commercially available since 1993, this nematode is also sold as a biological insecticide, where its excellent ability to persist and provide long-term control contributes to overall efficacy.
Heterorhabditis bacteriophora: Among the most economically important entomopathogenic nematodes, H. bacteriophora possesses considerable versatility, attacking lepidopterous and coleopterous insect larvae, among other insects. This cruiser species appears quite useful against root weevils, particularly black vine weevil where it has provided consistently excellent results in containerized soil. A warm temperature nematode, H. bacteriophora shows reduced efficacy when soil drops below 20°C.
Heterorhabditis indica: First discovered in India, this nematode is now known to be ubiquitous. Heterorhabditis indica is considered to be a heat tolerant nematode (infecting insects at 30 °C or higher). The nematode produces high yields in vivo and in vitro, but shelf life is generally shorter than most other nematode species.
Heterorhabditis megidis: First isolated in Ohio, this nematode is commercially available and marketed especially in western Europe for control of black vine weevil and various other soil insects. Heterorhabditis megidis is considered to be a cold tolerant nematode because it can effectively infect insects at temperatures below 15 °C.
Conservation strategies are poorly developed and largely limited to avoiding applications onto sites where the nematodes are ill-adapted; for example, where immediate mortality is likely (e.g., exposed foliage) or where they are completely ineffective (e.g., aquatic habitats) (Lewis et al., 1998). Minimizing deleterious effects of the aboveground environment with a post-application rinse that washes infective juveniles into the soil is also a useful approach to increasing persistence and efficacy. Native populations are highly prevalent, but, other than scattered reports of epizootics, their impact on host populations is generally not well documented (Stuart et al., 2006). This is largely attributable to the cryptic nature of soil insects. Consequently, research and guidelines for conserving native entomopathogenic nematodes are in need of advancement.
Infective juveniles are compatible with most but not all agricultural chemicals under field conditions. Compatibility has been tested with well over 100 different chemical pesticides. Entomopathogenic nematodes are compatible (e.g., may be tank-mixed) with most chemical herbicides and fungicides as well as many insecticides (such as bacterial or fungal products) (Koppenhöfer and Grewal, 2005). In fact, in some cases, combinations of chemical agents with nematodes results in synergistic levels of insect mortality. Some chemicals to be used with care or avoided include aldicarb, carbofuran, diazinon, dodine, methomyl, and various nematicides. However, specific interactions can vary based on the nematode and host species and application rates. Furthermore, even when a specific chemical pesticide is not deemed compatible, use of both agents (chemical and nematode) can be implemented by waiting an appropriate interval between applications (e.g., 1 – 2 weeks). Prior to use, compatibility and potential for tank-mixing should be based on manufacturer recommendations. Similarly, entomopathogenic nematodes are also compatible with many though not all biopesticides (Koppenhöfer and Grewal, 2005); interactions range from antagonism to additivity or synergy depending on the specific combination of control agents, target pest, and rates and timing of application. Nematodes are generally compatible with chemical fertilizers as well as composted manure though fresh manure can be detrimental.
Of the nearly eighty steinernematid and heterorhabditid nematodes identified to date, at least twelve species have been commercialized. A list of some nematode producers and suppliers is provided below; the list emphasizes U.S. suppliers. Comparison-shopping is recommended as prices vary greatly among suppliers. Additionally, caution is again advised with regard to application rates. One billion nematodes per acre (250,000 per m2) is the rule-of-thumb against most soil insects (containerized and greenhouse soils tend to be treated at higher rates). A final caveat is that, just as one must select the appropriate insecticide to control a target insect, so must one choose the appropriate nematode species or strain. Ask suppliers about field tests supporting their recommended matching of insect target and nematode.
SOME COMMERCIAL PRODUCERS/SUPPLIERS*
|A-1 Unique Insect Control
5504 Sperry Drive
Citrus Heights, CA 95621.
|Andermatt Biocontrol AG
Hb, Hmeg, Sc, Sf.
P.O. Box 4247 CRB
Tucson, AZ 85738-1247.
Hb, Sc, Sf.
801 Dayton Avenue
Ames, IA 50010 USA.
Hb, Hmeg, Sc, Sf, Sk, Sr, Ss.
|The Beneficial Insect Co.
PO Box 471143
Charlotte, NC 28247.
Springtown Road, P.O. Box 177
Willow Hill, PA 17271
Hb, Sc, Sf.
134 West Drive
Lodi, Ohio 44254.
FAX: 330-302-4204 ;
Klausdorfer Str. 28-36
5100 Schenley Place
Lawrenceburg, IN 47025.
128 Intervale Road
Burlington, VT 05401
Hb, Sc (mixture)
2725A Hwy 32 West
Chico CA 95973.
Hb, Sc (mixture)
|Green Spot, Ltd.
93 Priest Road
Nottingham, NH 03290-6204
Hb, Sc, Sf.
|Harmony Farm Supply & Nursery
3244 Hwy. 116 North
Sebastopol, CA 95472
P.O. Box 25845
Colorado Springs, CO 80936.
|IPM Laboratories, Inc.
Veilingweg 17, P.O. Box 155 2650
AD Berkel en Rodenrijs
Romulus, Michigan 48174
FAX: 734 641 3799
Hb, Hmeg, Sc, Sf.
|M & R Durango, Inc.
P.O. Box 886
Bayfield, CO 81122.
Hb, Sc, Sf.
|Natural Insect Control
3737 Netherby Rd,
Canada, L0S 1S0.
|Natural Pest Controls
8864 Little Creek Drive
Orangevale, CA 95662
P.O. Box 35
Medford, OR 97501
|Peaceful Valley Farm Supply
P.O. Box 2209
Grass Valley, CA 95945
|Do My Own Pest Control — Nematodes
4260 Communications Drive
Norcross, GA 30093
Toll Free: 866-581-7387
|Rincon-Vitova Insectaries Inc.
P.O. Box 1555
Ventura, CA 93002
Hb, Hi, Hmar, Sc, Sf.
|Southeastern Insectaries, Inc.
606 Ball Street or
P.O. Box 1546,
Perry, GA 31069
Hb, Hi, Sc.
|Territorial Seed Company
P.O. Box 157
Cottage Grove, OR 97424.
|Worm’s Way Inc.
7850 N. State Road 37
Bloomington, IN 47404.
7028 W. Waters Ave.,
Tampa, FL 33634-2292
Hb, Sc, Sf.
|Gulf Coast Biotics
P.O. Box 1291
Sanger, TX 76266
Note: nematode species associated with companies listed above reflect those found at the time this webpage was written; thus, species carried by each company may vary over time. Hb=Heterorhabditis bacteriophora, Hi = H. indica, Hmar = H. marelata, Hmeg = H. megidis, Sc=Steinernema carpocapsae, Sf=S. feltiae, Sk = S. kraussei, Sr=S. riobrave, Ss=S. scapterisci.
* Mention of a proprietary product name does not imply USDA’s approval of the product to the exclusion of others that may be suitable.
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Entomopathogenic nematode infective juvenile