-
ICMag with help from Landrace Warden and The Vault is running a NEW contest in November! You can check it here. Prizes are seeds & forum premium access. Come join in!
Dud Identification Collective Knowledge.
- Thread starter high life 45
- Start date
- Status
If anyone wants to swordfight, they can start another dick thread very easily.
Cmon now guys lets Keep things civil. Smoke a bowl and get along.
We got minds working together all over the world in this thread....lets keep working together, no need to encourage any immature behavior in this thread.
Big ups to str8edge for putting time in to get things tested.
Perhaps we will turn duds to studs by then end of this thread.
Cmon now guys lets Keep things civil. Smoke a bowl and get along.
We got minds working together all over the world in this thread....lets keep working together, no need to encourage any immature behavior in this thread.
Big ups to str8edge for putting time in to get things tested.
Perhaps we will turn duds to studs by then end of this thread.
how did you get pic's of my grow ? drone ? J/K. impressive.
Don't Mistaken CONFIDENCE for arrogance
Not everyone can be Michael Jordan or Kobe Bryant
You play a decent role off the bench of the RetroGrow.... I'll give you that...adequate Bench warmer
G`day Stormy
Nah your still a long way from being the Kobe or Micheal Jordan of Herb. How many rings or MVPs do you have ?
I`d rate you alongside there with Hamed Haddadi .A novelty but not an all star . 555!
Thanks for sharin
EB .
You have nice plants but a shity childish attitude.
You turn people off.
You grow weed, you're supposed to be turning people on.
You turn people off.
You grow weed, you're supposed to be turning people on.
Hall of Fame .....
You forgot the most RARE genetics in the Game.... MVP doesn't even fit....
Thanks for sharin.............
Hall of Fame .....
You forgot the most RARE genetics in the Game.... MVP doesn't even fit....
Thanks for sharin.............
G`day Stormy
I said it before , I`ll say it again .
Thanks for sharin
EB .
#NotInYourBag
How does one identify the exact nematode found??? I have added nematodes, to kill fungus gnats. Would they invade a plant?
Guess the real question is, are stem nematodes the only ones found in stems, including beneficial ones?
Is an extreme microscope needed (electron, etc.), for exact identification.
Did storm shadows show rings and damage like str8edge described? Do not remember seeing pictures.
I do believe that Storm Shadows problem is stem nematodes. My doubt is if it is everyone's problem.
Further testing need to be done, to say this issue is closed.
Guess the real question is, are stem nematodes the only ones found in stems, including beneficial ones?
Is an extreme microscope needed (electron, etc.), for exact identification.
Did storm shadows show rings and damage like str8edge described? Do not remember seeing pictures.
I do believe that Storm Shadows problem is stem nematodes. My doubt is if it is everyone's problem.
Further testing need to be done, to say this issue is closed.
Last edited:
I wonder if letting your growroom heat up to 115 F for a half hour would kill em off?
No. They thrive in heat, and would just burrow under the soil. But farmers do use plastic sheeting spread over the ground to let the sun heat up the topsoil to help control them, then they inject fumigants under the sheeting to finish them off. Every creature dies at a certain temperature, but not sure what that temperature would be for Ditylenchus dipsaci. Since I've never had these, difficult to say, but would be a good experiment for someone who does have them. The issue is killing them without killing the plants. There are 81 species of Ditylenchus dipsaci, making the task more difficult. 118F seems to be the temperature that kills them, at least in seeds and bulbs. In the ground is a different story, but would be a good experiment for someone that has these pests.
http://www.appsnet.org/publications/potm/pdf/Mar11.pdf
thats a seed hot water treatment exposure temperature time kill ratio chart
Heat treatments are the sliced bread of pest treatments, this grower I know had bms in veg, but his ac kept failing and he never had a problem with them in flower.
i bet several hours would do it. but the root zone is what would also be needed too. maybe a 115 drench at the end of the treatment period would be a good try at least. that said i would kill all moms if it were me and hot water treat all new fresh cuts of stuff i wanted to try to keep between cutting them and cloning them as described in the above chart
I only do for hobby, and would rather incinerate anything questionable. Understand those growing bulk, where legal, could have major financial losses.
I do not want to be typhoid Mary of my state.
I honestly do not know if I had this from Adubb seeds, or if they were just genetically screwed, and first few set of leaves twisted, and did not grow worth a crap, compared to others.
Just like when I walked in on girlfriend in 1980's banging some loser, was just glad I did not get aids, or anything else.
I do not want to be typhoid Mary of my state.
I honestly do not know if I had this from Adubb seeds, or if they were just genetically screwed, and first few set of leaves twisted, and did not grow worth a crap, compared to others.
Just like when I walked in on girlfriend in 1980's banging some loser, was just glad I did not get aids, or anything else.
Ditylenchus dipsaci
http://www.cabi.org/isc/datasheet/19287
Lots of info, here is some of it:
Hosts/Species Affected
D. dipsaci is known to attack over 450 different plant species, including many weeds (Goodey et al., 1965). However, it occurs in more than 20 biological races, some of which have a limited host range. The races that breed on rye, oats and onions seem to be polyphagous and can also infest several other crops, whereas those breeding on lucerne, Trifolium pratense and strawberries are virtually specific for their named hosts and appear to have relatively few alternative host plants. The tulip race will also infest Narcissus, whereas another race commonly found in Narcissus does not breed on tulip. It is known that some of the races can interbreed and that their progeny have different host preferences. See also Sturhan (1969) and Eriksson (1974). Sturhan and Brzeski (1991) briefly described 23 races, and three races that were raised to species or subspecies rank (Ditylenchus dipsaci falcariae, D. galeopsidis and D. sonchophila).
In addition to the hosts listed, Gnaphalium spicatum, Oxalis corniculata, Amaranthus deflexus and Eupatorium pauciflorum are reported as wild hosts of D. dipsaci.
Identity
Preferred Scientific Name
Ditylenchus dipsaci (Kühn, 1857) Filip'ev, 1936
Preferred Common Name
stem and bulb nematode
Other Scientific Names
Anguillula devastatrix Kühn, 1869
Anguillula dipsaci Kühn, 1857
Anguillula secalis Nitschke, 1868
Anguillulina dipsaci (Kühn, 1857) Gervais & Van Beneden, 1859
Anguillulina dipsaci var. communis Steiner & Scott, 1935
Ditylenchus allocotus (Steiner, 1934) Filip'ev & Sch. Stek., 1
Ditylenchus amsinckiae (Steiner & Scott, 1935) Filip'ev & Sch.
Ditylenchus dipsaci var. tobaensis Schneider, 1937
Ditylenchus fragariae Kir'yanova, 1951
Ditylenchus sonchophila Kir'yanova, 1958
Ditylenchus trifolii Skarbilivich, 1958
Tylenchus allii Beijerinck, 1883
Tylenchus devastator
Tylenchus devastatrix (Kühn) Oerley
Tylenchus dipsaci (Kühn, 1857) Bastian, 1865
Tylenchus havensteinii Kühn, 1881
Tylenchus hyacinthi Prillieux, 1881
Tylenchus putrefaciens Kühn, 1879
International Common Names
English: brown ring disease of hyacinth, bulb eelworm, onion bloat, ring disease of bulbs
Spanish: acebollado del centeno, anguilulosis de la avena, anguilulosis de la cebolla, cebollino del centeno, nematodo de la cebolla, nematodo del tallo
French: anguillule commune des tiges, anguillule des cereales et des bulbes, nématode des tiges, poireaute avoine, seigle oignonne
Local Common Names
Denmark: stængelnematod
Finland: varsiankeroinen
Germany: ruebenkopf-älchen, stengel-älchen, stock-älchen
Italy: anguillula delle piante erbacee
Japan: kuki-sentyubyo, nami-kuki-sentyu
Netherlands: stengelaaltje
Norway: stengelnematode
Sweden: stjälknematod
Turkey: sogan sak nematodo
EPPO code
DITYDI (Ditylenchus dipsaci)
Taxonomic Tree
Domain: Eukaryota
Kingdom: Metazoa
Phylum: Nematoda
Family: Anguinidae
Genus: Ditylenchus
Species: Ditylenchus dipsaci
Notes on Taxonomy and Nomenclature
Ditylenchus dipsaci exhibits considerable variation with external factors, such as temperature, and it has several host races. Its chromosome number has been reported from a number of hosts and geographical origins and it varies from n = 6 to 30 (Sturhan and Brzeski, 1991). Not surprisingly, several species have been described with morphological characteristics that fall within the range of variation of D. dispaci. Some of these species are local variants of D. dipsaci and should be treated as synonyms of this species. Others, such as D. phloxidis, are unable to cross with D. dipsaci (Ladygina, 1974) and are considered to be valid species (Fortuner, 1982). Some authors lump all the morphologically indistinguishable species into a collective species, D. dipsaci (Sturhan and Brzeski, 1991). Summarizing several years of studies in Russia on the question (Barabashova, 1972, 1974, 1975, 1976, 1978, 1979; Ladygina, 1974, 1976), Ladygina and Barabashova (1980) consider that two groups may be distinguished in the Ditylenchus dipsaci complex. The parasites of cultivated plants form a fairly homologous group as to morphology and chromosome number (n = 12) in all but the 'giant race', parasitic in Vicia faba var. equina, where n = 27. Most of the races in this first group cross-breed successfully. The second group, parasites of wild plants, forms a heterogeneous group both in karyotype (n = 18 to 28) and morphology. At least partial incompatibility is observed between races in the second group. The two groups are genetically incompatible.
To conclude, there seem to exist two or more valid species in the D. dipsaci complex, but they have not yet been validly or completely described and differentiated.
Detection and Inspection
D. dipsaci can be isolated from samples of suspected seed material (according to symptoms) by dissection in water at 20 times magnification. A sample of a minimum of 300 seeds should be examined. The seed is submerged for 24 hours in 500-1000 ml of water, insuring sufficient oxygen for the nematode mobility and survival. An extraction temperature of 10°C is the optimum for nematode extraction and simultaneously reducing turbidity of the solution. The nematodes in the solution are concentrated by decantation through a 25 µm sieve and are then counted (Augustin and Sikora, 1989b). Microscopic examination at 1000 times magnification is necessary for correct identification of the nematode species.
Studies have been made for species identification based on DNA probes (Palmer et al., 1991), monoclonal antibodies (Palmer et al., 1992) and restriction fragment length polymorphisms (Wendt et al., 1994). These molecular methods are very promising, but not yet used routinely. Electrophoretic techniques (Bossis et al., 1998; Tenente and Evans, 1998) and random amplified polymorphic DNA (Esquibet et al., 1998) can be used to identify populations of D. dispaci.
The species morphologically indistinguishable from D. dipsaci cannot be identified by host differentials because of the within-race variations and because some of the races freely interbreed, giving hybrids with host characteristics intermediate between those of their parents (Sturhan and Brzeski, 1991). D. dipsaci can be distinguished from D. destructor by observation of the spiculum shape (Karssen and Willemsen, 2010).
Seed Health Tests
Sieve test (Augustin and Sikora, 1989b)
- A sample of a minimum of 300 seeds should be examined.
- The seed is submerged for 24 h in 500-1000 ml of water, insuring sufficient oxygen for the nematode mobility and survival. An extraction temperature of 10°C is the optimum for nematode extraction and simultaneously reducing turbidity of the solution.
- The nematodes in the solution are concentrated by decantation through a 25 µm sieve and are then counted.
- Microscopic examination at 1000 times magnification is necessary for correct identification of the nematode species.
Seed Treatment
Chemical
Treatment of seeds with nematicides or insecticides to control seed transmission of the pathogen has had mixed success (Schiffers et al., 1984; Caubel et al., 1985; Whitehead and Tite, 1987; Adamova and Rotrekl, 1991; Hooper, 1991). Treatment of infected garlic cloves with abamectin resulted in a 56% yield increase and eliminated all nematodes in 93% of bulbs produced (Becker, 1999) but bulbs subjected to a combination of this chemical and hot-water treatment were somewhat damaged (Jaehn and Kimoto, 1996). In the UK, the best results against the stem nematode in Narcissus were obtained when formaldehyde or peracetic acid (at 1.0 and 1.5%) were used in combination with thiabendazole (Hanks and Linfield, 1999).
Ciesla et al. (2010) suggest that methyl iodide could be used as a fumigant to eradicate D. dipsaci from alfalfa seeds. Man?asová et al. (2012) propose the use of hydrogen cyanide gas to remove D. dipsaci from seed material.
Physical
Hot-water treatments with different temperature-time combinations, depending on type and state of seed material, can be an efficient means of controlling D. dipsaci (Gratwick and Southey, 1972). Commercial cleaning of the seed has proven to be effective in removing the nematodes along with associated plant debris (Wood and Close, 1974; Neergaard, 1977).
Pathogen Transmission
Seed
Seed transmission of D. dipsaci to the planted crop is well established. Seinhorst and Koert (1971) found a strong correlation between the number of nematodes/g of seed and percentage of infected onion bulbs. Aerial photography of three fields of lucerne in the UK were used to monitor the spread of a seedborne infestation of D. dipsaci. Results from the use of an image analyser suggested that infestation develops by the generation of additional colonies from the original foci and by the progressive expansion of the area damaged by an established colony (Atkinson and Sykes, 1981). Planting certified nematode-free seeds is recognized as an important control practice for this disease. In Germany, a tolerance level of five nematodes/300 seeds is used to establish the risk of transmission of the pathogen to seedlings (Knuth, 1993).
Other sources
Nematode-infested soil is an important inoculum source of D. dipsaci. The number of nematodes/500g of soil were well correlated with the number/50 g of harvested onion seeds (Seinhorst and Koert, 1971). A tolerance threshold of 2-3 nematodes/250 cm³ soil is used in Germany to indicate risk of plant infection (Knuth, 1993). D. dipsaci-infested weeds are also recognized as a potentially important inoculum source of this nematode (Gentzsch, 1973).
Incidence
D. dipsaci has been shown to be seedborne on about 15 plant species (Neergaard, 1977). A survey of commercial seeds samples in the UK showed its widespread occurrence in economically important crops including 36-45% of seed stocks of broad been, red beet and carrots, 14-17% of shallots and runner beans and >3% of peas, onions and leeks (Green and Sime, 1979). High incidences of seed infection have been reported, e.g. 67% in broad bean seeds (Steiner and Lamprecht, 1983). Goodey (1945) traced invasion of D. dipsaci through the pedicel and placenta of the onion mother plant into the ovary wall and later through the short funiculus from which the nematodes become attached to the seed primarily in the vicinity of the hilum The nematode has also been located below the seed coat of Vicia faba (Neergaard, 1977). The pathogen was found in 1-40% of V. faba seeds in Algeria (Sellami et al., 1998).
The distribution of D. dipsaci between seeds in infested samples of broad bean seed was shown to be skewed so that the nematodes were concentrated on a few seeds (Green, 1979). Numbers of nematodes within individual seeds may vary substantially. In one of two samples of seed of Vicia faba, all stages of D. dipsaci were found. The other sample (50 seeds) was negative. In 20 seeds of the infected sample there were 20,035 larvae (over 8000 on one seed) (Pereira and Santos, 1975).
Biology and Ecology
D. dipsaci is a migratory endoparasite that feeds upon parenchymatous tissue in stems and bulbs, causing the breakdown of the middle lamellae of cell walls. Feeding often causes swellings and distortion of aerial plant parts (stems, leaves, flowers) and necrosis or rotting of stem bases, bulbs, tubers and rhizomes. During cold storage of bulbs and tubers, D. dipsaci and rotting may continue to develop.
In onion plants at 15°C, the lifecycle takes approximately 20 days. The duration of the life cycle depends on the temperature and differs among isolates of different origins. Maximum activity and invasive ability is generally between 10 and 20°C. Females lay 200-500 eggs each. Fourth-stage juveniles tend to aggregate on or just below the surface of heavily infested tissue to form clumps of 'eelworm wool' and can survive in dry conditions for several years; they may also become attached to the seeds of host plants such as onions, lucerne, Trifolium pratense, faba beans and Phlox drummondii. In clay soils, D. dipsaci may persist for many years. Cool, moist conditions favour invasion of young plant tissue by this nematode.
Means of Movement and Dispersal
In international trade D. dipsaci is liable to be carried on dry seeds and planting material of host plants. In the field the fourth-stage juvenile can withstand desiccation for many years, and although soil densities seem to decrease rapidly, the nematode can survive for years without a host plant. Desiccation of D. dipsaci causes some ultrastructural changes (Wharton, 1996; Wharton and Lemmon, 1998). Following a period of desiccation and re-immersion in water, recovery occurs after a delay (lag phase) showing that repairs or restoration of a normal physiological state are necessary before activity can resume (Wharton et al., 1999). Nematode survival and damage are greater in heavy soils as compared to sandy soils. It can also survive on a number of weeds. Irrigation water and cultivation by contaminated farm tools and machinery are also sources of inoculum dissemination.
Sanitation
Certified nematode-free seeds and planting material are most essential to prevent crop damage by D. dipsaci. Hot-water treatments with different temperature-time combinations, depending on type and state of seed material, are operational and efficient to control D. dipsaci (Gratwick and Southey, 1972). Hot-water treatment of narcissus bulbs infected with stem nematodes consist either of storage for 1-2 weeks at 25-30°C, followed by soaking in water for 24 h and hot-water treatment at 45°C for 4 h, or storage for 1-2 weeks at 25-30°C, followed by hot-water treatment at 47°C for 4 h. Routine hot-water treatment for the control of other pests and diseases should be carried out at 43.5°C for 3 h to control any slight, possibly unnoticed nematode infection (Windrich, 1973).
-SamS
http://www.cabi.org/isc/datasheet/19287
Lots of info, here is some of it:
Hosts/Species Affected
D. dipsaci is known to attack over 450 different plant species, including many weeds (Goodey et al., 1965). However, it occurs in more than 20 biological races, some of which have a limited host range. The races that breed on rye, oats and onions seem to be polyphagous and can also infest several other crops, whereas those breeding on lucerne, Trifolium pratense and strawberries are virtually specific for their named hosts and appear to have relatively few alternative host plants. The tulip race will also infest Narcissus, whereas another race commonly found in Narcissus does not breed on tulip. It is known that some of the races can interbreed and that their progeny have different host preferences. See also Sturhan (1969) and Eriksson (1974). Sturhan and Brzeski (1991) briefly described 23 races, and three races that were raised to species or subspecies rank (Ditylenchus dipsaci falcariae, D. galeopsidis and D. sonchophila).
In addition to the hosts listed, Gnaphalium spicatum, Oxalis corniculata, Amaranthus deflexus and Eupatorium pauciflorum are reported as wild hosts of D. dipsaci.
Identity
Preferred Scientific Name
Ditylenchus dipsaci (Kühn, 1857) Filip'ev, 1936
Preferred Common Name
stem and bulb nematode
Other Scientific Names
Anguillula devastatrix Kühn, 1869
Anguillula dipsaci Kühn, 1857
Anguillula secalis Nitschke, 1868
Anguillulina dipsaci (Kühn, 1857) Gervais & Van Beneden, 1859
Anguillulina dipsaci var. communis Steiner & Scott, 1935
Ditylenchus allocotus (Steiner, 1934) Filip'ev & Sch. Stek., 1
Ditylenchus amsinckiae (Steiner & Scott, 1935) Filip'ev & Sch.
Ditylenchus dipsaci var. tobaensis Schneider, 1937
Ditylenchus fragariae Kir'yanova, 1951
Ditylenchus sonchophila Kir'yanova, 1958
Ditylenchus trifolii Skarbilivich, 1958
Tylenchus allii Beijerinck, 1883
Tylenchus devastator
Tylenchus devastatrix (Kühn) Oerley
Tylenchus dipsaci (Kühn, 1857) Bastian, 1865
Tylenchus havensteinii Kühn, 1881
Tylenchus hyacinthi Prillieux, 1881
Tylenchus putrefaciens Kühn, 1879
International Common Names
English: brown ring disease of hyacinth, bulb eelworm, onion bloat, ring disease of bulbs
Spanish: acebollado del centeno, anguilulosis de la avena, anguilulosis de la cebolla, cebollino del centeno, nematodo de la cebolla, nematodo del tallo
French: anguillule commune des tiges, anguillule des cereales et des bulbes, nématode des tiges, poireaute avoine, seigle oignonne
Local Common Names
Denmark: stængelnematod
Finland: varsiankeroinen
Germany: ruebenkopf-älchen, stengel-älchen, stock-älchen
Italy: anguillula delle piante erbacee
Japan: kuki-sentyubyo, nami-kuki-sentyu
Netherlands: stengelaaltje
Norway: stengelnematode
Sweden: stjälknematod
Turkey: sogan sak nematodo
EPPO code
DITYDI (Ditylenchus dipsaci)
Taxonomic Tree
Domain: Eukaryota
Kingdom: Metazoa
Phylum: Nematoda
Family: Anguinidae
Genus: Ditylenchus
Species: Ditylenchus dipsaci
Notes on Taxonomy and Nomenclature
Ditylenchus dipsaci exhibits considerable variation with external factors, such as temperature, and it has several host races. Its chromosome number has been reported from a number of hosts and geographical origins and it varies from n = 6 to 30 (Sturhan and Brzeski, 1991). Not surprisingly, several species have been described with morphological characteristics that fall within the range of variation of D. dispaci. Some of these species are local variants of D. dipsaci and should be treated as synonyms of this species. Others, such as D. phloxidis, are unable to cross with D. dipsaci (Ladygina, 1974) and are considered to be valid species (Fortuner, 1982). Some authors lump all the morphologically indistinguishable species into a collective species, D. dipsaci (Sturhan and Brzeski, 1991). Summarizing several years of studies in Russia on the question (Barabashova, 1972, 1974, 1975, 1976, 1978, 1979; Ladygina, 1974, 1976), Ladygina and Barabashova (1980) consider that two groups may be distinguished in the Ditylenchus dipsaci complex. The parasites of cultivated plants form a fairly homologous group as to morphology and chromosome number (n = 12) in all but the 'giant race', parasitic in Vicia faba var. equina, where n = 27. Most of the races in this first group cross-breed successfully. The second group, parasites of wild plants, forms a heterogeneous group both in karyotype (n = 18 to 28) and morphology. At least partial incompatibility is observed between races in the second group. The two groups are genetically incompatible.
To conclude, there seem to exist two or more valid species in the D. dipsaci complex, but they have not yet been validly or completely described and differentiated.
Detection and Inspection
D. dipsaci can be isolated from samples of suspected seed material (according to symptoms) by dissection in water at 20 times magnification. A sample of a minimum of 300 seeds should be examined. The seed is submerged for 24 hours in 500-1000 ml of water, insuring sufficient oxygen for the nematode mobility and survival. An extraction temperature of 10°C is the optimum for nematode extraction and simultaneously reducing turbidity of the solution. The nematodes in the solution are concentrated by decantation through a 25 µm sieve and are then counted (Augustin and Sikora, 1989b). Microscopic examination at 1000 times magnification is necessary for correct identification of the nematode species.
Studies have been made for species identification based on DNA probes (Palmer et al., 1991), monoclonal antibodies (Palmer et al., 1992) and restriction fragment length polymorphisms (Wendt et al., 1994). These molecular methods are very promising, but not yet used routinely. Electrophoretic techniques (Bossis et al., 1998; Tenente and Evans, 1998) and random amplified polymorphic DNA (Esquibet et al., 1998) can be used to identify populations of D. dispaci.
The species morphologically indistinguishable from D. dipsaci cannot be identified by host differentials because of the within-race variations and because some of the races freely interbreed, giving hybrids with host characteristics intermediate between those of their parents (Sturhan and Brzeski, 1991). D. dipsaci can be distinguished from D. destructor by observation of the spiculum shape (Karssen and Willemsen, 2010).
Seed Health Tests
Sieve test (Augustin and Sikora, 1989b)
- A sample of a minimum of 300 seeds should be examined.
- The seed is submerged for 24 h in 500-1000 ml of water, insuring sufficient oxygen for the nematode mobility and survival. An extraction temperature of 10°C is the optimum for nematode extraction and simultaneously reducing turbidity of the solution.
- The nematodes in the solution are concentrated by decantation through a 25 µm sieve and are then counted.
- Microscopic examination at 1000 times magnification is necessary for correct identification of the nematode species.
Seed Treatment
Chemical
Treatment of seeds with nematicides or insecticides to control seed transmission of the pathogen has had mixed success (Schiffers et al., 1984; Caubel et al., 1985; Whitehead and Tite, 1987; Adamova and Rotrekl, 1991; Hooper, 1991). Treatment of infected garlic cloves with abamectin resulted in a 56% yield increase and eliminated all nematodes in 93% of bulbs produced (Becker, 1999) but bulbs subjected to a combination of this chemical and hot-water treatment were somewhat damaged (Jaehn and Kimoto, 1996). In the UK, the best results against the stem nematode in Narcissus were obtained when formaldehyde or peracetic acid (at 1.0 and 1.5%) were used in combination with thiabendazole (Hanks and Linfield, 1999).
Ciesla et al. (2010) suggest that methyl iodide could be used as a fumigant to eradicate D. dipsaci from alfalfa seeds. Man?asová et al. (2012) propose the use of hydrogen cyanide gas to remove D. dipsaci from seed material.
Physical
Hot-water treatments with different temperature-time combinations, depending on type and state of seed material, can be an efficient means of controlling D. dipsaci (Gratwick and Southey, 1972). Commercial cleaning of the seed has proven to be effective in removing the nematodes along with associated plant debris (Wood and Close, 1974; Neergaard, 1977).
Pathogen Transmission
Seed
Seed transmission of D. dipsaci to the planted crop is well established. Seinhorst and Koert (1971) found a strong correlation between the number of nematodes/g of seed and percentage of infected onion bulbs. Aerial photography of three fields of lucerne in the UK were used to monitor the spread of a seedborne infestation of D. dipsaci. Results from the use of an image analyser suggested that infestation develops by the generation of additional colonies from the original foci and by the progressive expansion of the area damaged by an established colony (Atkinson and Sykes, 1981). Planting certified nematode-free seeds is recognized as an important control practice for this disease. In Germany, a tolerance level of five nematodes/300 seeds is used to establish the risk of transmission of the pathogen to seedlings (Knuth, 1993).
Other sources
Nematode-infested soil is an important inoculum source of D. dipsaci. The number of nematodes/500g of soil were well correlated with the number/50 g of harvested onion seeds (Seinhorst and Koert, 1971). A tolerance threshold of 2-3 nematodes/250 cm³ soil is used in Germany to indicate risk of plant infection (Knuth, 1993). D. dipsaci-infested weeds are also recognized as a potentially important inoculum source of this nematode (Gentzsch, 1973).
Incidence
D. dipsaci has been shown to be seedborne on about 15 plant species (Neergaard, 1977). A survey of commercial seeds samples in the UK showed its widespread occurrence in economically important crops including 36-45% of seed stocks of broad been, red beet and carrots, 14-17% of shallots and runner beans and >3% of peas, onions and leeks (Green and Sime, 1979). High incidences of seed infection have been reported, e.g. 67% in broad bean seeds (Steiner and Lamprecht, 1983). Goodey (1945) traced invasion of D. dipsaci through the pedicel and placenta of the onion mother plant into the ovary wall and later through the short funiculus from which the nematodes become attached to the seed primarily in the vicinity of the hilum The nematode has also been located below the seed coat of Vicia faba (Neergaard, 1977). The pathogen was found in 1-40% of V. faba seeds in Algeria (Sellami et al., 1998).
The distribution of D. dipsaci between seeds in infested samples of broad bean seed was shown to be skewed so that the nematodes were concentrated on a few seeds (Green, 1979). Numbers of nematodes within individual seeds may vary substantially. In one of two samples of seed of Vicia faba, all stages of D. dipsaci were found. The other sample (50 seeds) was negative. In 20 seeds of the infected sample there were 20,035 larvae (over 8000 on one seed) (Pereira and Santos, 1975).
Biology and Ecology
D. dipsaci is a migratory endoparasite that feeds upon parenchymatous tissue in stems and bulbs, causing the breakdown of the middle lamellae of cell walls. Feeding often causes swellings and distortion of aerial plant parts (stems, leaves, flowers) and necrosis or rotting of stem bases, bulbs, tubers and rhizomes. During cold storage of bulbs and tubers, D. dipsaci and rotting may continue to develop.
In onion plants at 15°C, the lifecycle takes approximately 20 days. The duration of the life cycle depends on the temperature and differs among isolates of different origins. Maximum activity and invasive ability is generally between 10 and 20°C. Females lay 200-500 eggs each. Fourth-stage juveniles tend to aggregate on or just below the surface of heavily infested tissue to form clumps of 'eelworm wool' and can survive in dry conditions for several years; they may also become attached to the seeds of host plants such as onions, lucerne, Trifolium pratense, faba beans and Phlox drummondii. In clay soils, D. dipsaci may persist for many years. Cool, moist conditions favour invasion of young plant tissue by this nematode.
Means of Movement and Dispersal
In international trade D. dipsaci is liable to be carried on dry seeds and planting material of host plants. In the field the fourth-stage juvenile can withstand desiccation for many years, and although soil densities seem to decrease rapidly, the nematode can survive for years without a host plant. Desiccation of D. dipsaci causes some ultrastructural changes (Wharton, 1996; Wharton and Lemmon, 1998). Following a period of desiccation and re-immersion in water, recovery occurs after a delay (lag phase) showing that repairs or restoration of a normal physiological state are necessary before activity can resume (Wharton et al., 1999). Nematode survival and damage are greater in heavy soils as compared to sandy soils. It can also survive on a number of weeds. Irrigation water and cultivation by contaminated farm tools and machinery are also sources of inoculum dissemination.
Sanitation
Certified nematode-free seeds and planting material are most essential to prevent crop damage by D. dipsaci. Hot-water treatments with different temperature-time combinations, depending on type and state of seed material, are operational and efficient to control D. dipsaci (Gratwick and Southey, 1972). Hot-water treatment of narcissus bulbs infected with stem nematodes consist either of storage for 1-2 weeks at 25-30°C, followed by soaking in water for 24 h and hot-water treatment at 45°C for 4 h, or storage for 1-2 weeks at 25-30°C, followed by hot-water treatment at 47°C for 4 h. Routine hot-water treatment for the control of other pests and diseases should be carried out at 43.5°C for 3 h to control any slight, possibly unnoticed nematode infection (Windrich, 1973).
-SamS
Last edited:
- Status
