''Pratylenchus'' is a genus of

nematode The nematodes ( or grc-gre, Νηματώδη; la, Nematoda) or roundworms constitute the phylum Nematoda (also called Nemathelminthes), with plant-Parasitism, parasitic nematodes also known as eelworms. They are a diverse animal phylum inhab ...

s known commonly as lesion nematodes.Crow, W. T
Amaryllis lesion nematode, ''Pratylenchus hippeastri''.
EENY-546. University of Florida IFAS. 2012. They are

parasitic Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has c ...

on plants and are responsible for root lesion disease on many taxa of host plants in

temperate In geography, the temperate climates of Earth occur in the middle latitudes (23.5° to 66.5° N/S of Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ranges throughout t ...

regions around the world. Lesion nematodes are migratory endoparasites that feed and reproduce in the

root In vascular plants, the roots are the organs of a plant that are modified to provide anchorage for the plant and take in water and nutrients into the plant body, which allows plants to grow taller and faster. They are most often below the sur ...

and move around, unlike the

cyst A cyst is a closed sac, having a distinct envelope and cell division, division compared with the nearby Biological tissue, tissue. Hence, it is a cluster of Cell (biology), cells that have grouped together to form a sac (like the manner in which ...

root-knot nematode Root-knot nematodes are plant-parasitic nematodes from the genus ''Meloidogyne''. They exist in soil in areas with hot climates or short winters. About 2000 plants worldwide are susceptible to infection by root-knot nematodes and they cause appr ...

s, which may stay in one place. They usually only feed on the cortex of the root.Lesion nematodes.
University of Illinois Extension. 1999. Species are distinguished primarily by the

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines * Morphology (archaeology), study of the shapes or forms of artifacts * Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies ...

of the stylets.Norton, D. C. ''Ecology of Plant-Parasitic Nematodes''. 1978.

Hosts and symptoms

Root lesion nematodes infect a great variety of hosts. ''Pratylenchus penetrans'' alone has over 350 host plants. They include agricultural crops such as

soybean The soybean, soy bean, or soya bean (''Glycine max'') is a species of legume native to East Asia, widely grown for its edible bean, which has numerous uses. Traditional unfermented food uses of soybeans include soy milk, from which tofu an ...

potato The potato is a starchy food, a tuber of the plant ''Solanum tuberosum'' and is a root vegetable native to the Americas. The plant is a perennial in the nightshade family Solanaceae. Wild potato species can be found from the southern Unit ...

es,

corn Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American and Australian English), is a cereal grain first domesticated by indigenous peoples in southern Mexico about 10,000 years ago. Th ...

banana A banana is an elongated, edible fruit – botanically a berry – produced by several kinds of large herbaceous flowering plants in the genus ''Musa''. In some countries, bananas used for cooking may be called "plantains", distinguis ...

s, and

wheat Wheat is a grass widely cultivated for its seed, a cereal grain that is a worldwide staple food. The many species of wheat together make up the genus ''Triticum'' ; the most widely grown is common wheat (''T. aestivum''). The archaeologi ...

. The genus is found most often in corn. Signs of disease are similar in most plants and generally include

necrotic Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. Necrosis is caused by factors external to the cell or tissue, such as infection, or trauma which result in the unregulated dige ...

lesion A lesion is any damage or abnormal change in the tissue of an organism, usually caused by disease or trauma. ''Lesion'' is derived from the Latin "injury". Lesions may occur in plants as well as animals. Types There is no designated classifi ...

s of the roots. The lesions can also be entrances for pathogenic bacteria and fungi, which produce secondary infections. Above ground the plant becomes stunted,

chlorotic In botany, chlorosis is a condition in which leaves produce insufficient chlorophyll. As chlorophyll is responsible for the green color of leaves, chlorotic leaves are pale, yellow, or yellow-white. The affected plant has little or no ability to ...

, and wilted, and it often dies. A crop field may be patchy as plants wither and die. Root lesion nematodes can cause significant yield losses.Barker, K. R., et al. ''Plant Nematode Interactions''. Madison: American Society of Agronomy, Inc. 1998.

Environment

''Pratylenchus'' abundance is affected by soil moisture, mineral components, temperature, aeration, organic matter, and pH. They are more common in sandy soils and land with

weed A weed is a plant considered undesirable in a particular situation, "a plant in the wrong place", or a plant growing where it is not wanted.Harlan, J. R., & deWet, J. M. (1965). Some thoughts about weeds. ''Economic botany'', ''19''(1), 16-24. ...

infestations.Hallmann, J., et al. (2007)
Occurrence and importance of plant-parasitic nematodes in organic farming in Germany.
''Nematology'' 9(6), 869-79. ''Pratylenchus'' can endure a wide range of environmental conditions. Moist temperate soils are ideal conditions for breeding and migrating underground, but they can persist in warm and dryer environments. In very dry conditions they are quiescent until moisture increases and plants resume growth.Agrios, G. N. ''Plant Pathology'' 5th ed. p. 852. Most lesion nematodes remain inactive when soil temperatures are below 59 °F (15 °C) and are not fully active until temperatures rise above 68 °F (20 °C).

Management

One common management option for crop-pest lesion nematodes is soil fumigation and

nematicide A nematicide is a type of chemical pesticide used to kill plant-parasitic nematodes. Nematicides have tended to be broad-spectrum toxicants possessing high volatility or other properties promoting migration through the soil. Aldicarb (Temik), a car ...

s. This is not effective for all species, and can be expensive for growers.Dropkin, V. H. ''Introduction to Plant Nematology'', 2nd ed. New York: John Wiley & Sons. 1989. Water immersion is another option. Infected plants are immersed in a hot water bath for about 30 minutes, which rids them of nematodes but does not harm the plant. This method has been successful for ''P. coffeae''. Crop rotation can help control the nematode load in the soil because different plants are susceptible to different ''Pratylenchus'' species.Saxena, G. and K. G. Mukerji. ''Management of Nematode and Insect-Borne Plant Diseases''. New York: The Haworth Press. 2007. Selecting resistant plant varieties and

cultivar A cultivar is a type of cultivated plant that people have selected for desired traits and when propagated retain those traits. Methods used to propagate cultivars include: division, root and stem cuttings, offsets, grafting, tissue culture, ...

s can reduce nematode problems. This is currently the only option for control of ''P. vulnus'', for example.

Life cycle and pathology

Female nematodes lay single eggs in the root or in the soil. They reproduce via

parthenogenesis Parthenogenesis (; from the Greek grc, παρθένος, translit=parthénos, lit=virgin, label=none + grc, γένεσις, translit=génesis, lit=creation, label=none) is a natural form of asexual reproduction in which growth and development ...

, laying fertile eggs without fertilization. In many species, males are rare.

References

External links

''Pratylenchus hippeastri''
on the UF / IFAS Featured Creatures website. {{Taxonbar, from=Q3401434 Soybean diseases Potato diseases Cereal diseases Secernentea genera