Nematodes in Agriculture
Today, we learn about plant nematodes in agriculture and their control methods.
Plant Parasitic Nematodes in Agriculture:
Many Farmers are nowadays facing heavy crop losses in Fruit Crops and Vegetable crops due to various unpredictable diseases caused by Nematodes. A typical example is Guava wilt caused by a nematode Guava wilt Nematode Meloidogyneenterlobii which is infested from foreign countries and it is infested into south India due to poor domestic as well as international plant quarantine measures. The Guava Wilt Nematode has caused heavy crop losses due to an infestation of the Nematode. There are also some examples like Golden Nematode on Potato etc. Therefore, we have come with this information on Nematodes and How to control Nematodes in Fruit and Vegetable Crops.
What are Nematodes:
Nematodes are triploblastic, bilaterally symmetrical, unsegmented, with 4 hypodermal chords, triradiate oesophagus, pseudoceolomicinvertebrates, with nerve ring circum oesophageal, however lacking respiratory and circulatory systems. Simply Nematodes are Worms that are a thread like or resembles thread. They are also known as eelworms or roundworms denoting their shape. The word Nematodes is derived from the Greek language. Nematodes are known as Nema as their nickname in the US.
How Nematodes cause disease to Plants:
Nematodes that cause diseases to plants are known as Plant-parasitic Nematodes. However, there also exist free-living nematodes that are not at all harmful to plants. In this post, we will let you know how to identify plant-parasitic nematodes from free-living nematodes. Plant parasitic nematodes are provided with special organs known as stylets that help in piercing the plant cells and penetrating into the plant cells. There are also Nematodes that cause diseases to humans and animals like intestinal roundworm in human intestine that causes anemia. The scientific name of this human parasitic nematode is Ascarislumbricoides. There also exist more human and animal pathogenic nematodes.
Where do Nematodes live at: Most of the plant parasitic Nematodes live in the Rhizosphere of agriculture crops. However, there also exists foliar nematodes that feed on the foliage of agricultural economic important crops.
Economic Importance of Nematodes in Agriculture:
- Being obligate and plant parasitic, there has been a record of 1800 species of Plant Parasitic Nematodes.
- Annually, Nematodes cause 12% to 13% of agriculture losses in the world. Prof. J.N. Sasser has led the first way to authenticate and estimate the economic losses caused by plant parasitic nematodes.
- Nematodes had caused 11% annual losses in vegetable crops in the US which is estimated to an economic loss of $267 mil/year.
- In India, Rajasthan has faced an annual loss of Rs. 32 mil and Rs. 25 mil in wheat and Barley crops due to the infestation of Cereal Cyst Nematode, Heteroderaavenae.
- In Northern regions, Seed Gall Nematode Anguinatritici in combination with bacteria caused heavy losses up to Rs. 70 mil in the Wheat crop.
- In Karnataka, Lesion Nematodes, Pratylenchus coffee had infested around 1k ha of coffee estates.
- Besides, these there are numerous crops infested with this plant-parasitic nematodes. Among which, vegetables are nowadays highly susceptible to plant parasitic nematodes.
- Most of the farmers are unable to diagnose the disease caused by the Nematodes as they live in the rhizosphere and typical symptoms are only visible on the hosts. However, fewer symptoms are seen on the foliage of agriculture crops.
Favorable conditions for Nematodes in Agriculture crops:
- The growth and development of Plant-parasitic Nematodes are favored by various environmental conditions especially the rhizosphere ecosystem play an important role.
- Plant Parasitic Nematodes as they feed on the roots their presence depends on the deeper root system. However, most of them are confined up to a depth of 25 to 30 cm below the soil.
- Soil temperature: 15 – 30°C. Also survive at 5 and 40°C.
- Soil humidity or soil moisture: 40% to 60%.
- Soil texture: Light soils are most favorable.
- Osmotic pressure: 10 atm.
- Soil pH: Between 4 – 8 pH.
- Soil microbes: Sometimes, Nematode infestation may lead to the incidence of various plant pathogens as plant are susceptible to diseases after infestation by plant parasitic nematodes.
Classification of Plant Parasitic Nematodes:
Plant Parasitic Nematodes are mainly classified into two type’s viz., phytonematodes above ground parts and PhtoNematodes below ground parts
Plant Parasitic Nematodes above ground parts:
These are the Plant pArasitic Nematodes that parasites on above ground level parts that is a foliar region or foliage i.e., leaves, stems and flowers, and seeds.
Gall-forming Nematodes: Wheat Seed Gall Nematode – Anguinatritici
Leaf gall Nematode – Anguinabalsamophila
Non – gall forming Nematodes: Stem Nematode – Ditylnechusdipsaci and Ditylenchusangustus
Foliar Nematode – Aphelenchoidesritzemabozi and Aphelenchoidesfragariae
Plant Parasitic Nematodes below ground parts:
These rhizosphere Nematodes constitute the Nematodes that causes major economic losses in agriculture and horticultural crops.
Sting Nematode – Belonolaimus sp.
Dagger Nematode – Xiphenema sp.
Needle Nematode – Longidorus sp.
Stubby Root Nematodes – Trichodorus sp.
Sheath Nematode – Hemicycliophoraareneria
Sessile Nematode – Cacoparuspestis
Migratory Semi Endoparasites:
Spiral Nematode – Helicotylenchussp.
Lance Nematode – Haplolaimus sp.
Stunt Nematodes – Tylenchorynchus sp.
Sedentary Semi Endoparasites:
Citrus Nematode – Tylenchulussemipenetrans
Reniform Nematode – Rotylenchusreniformis
Lesion Nematodes – Pratylenchus sp.
Rice root Nematode – Hirschmaniella sp.
Burrowing Nematode – Radopholussimilis
Root knot Nematode –Medoidogyne sp.
Cyst Nematode – Globodera sp. and Heterdera sp.
How to control Plant Parasitic Nematodes in Fruits and Vegetable Crops:
Management of Plant Parasitic Nematodes is difficult but easy if we go for some mandate precautions or Good Agriculture Practices(GAP) in our farm. As Plant Parasitic Nematodes can survive and adapt to vast environmental conditions, they are somehow difficult to control them.
Cultural Methods for Nematode control
- Crop Rotation
- Healthy plant material propagation in fruit crops and whenever necessary
- Proper application of organic amendments in the field
- Cultivation of Trap crops or antagonistic crops
- Sowing time (either early or late)
- Soil solarisation
Physical Methods of Nematode Management
Nematodes cant thrive temperature above 40°C. Therefore, the seedling material is done with Hot water treatment at the rate of seed or seedling dip in 54 to 55°C water for about 10 to 15 min. However, there also exist some other methods like irradiation, osmotic pressure and ultrasonic treatments which are rarely used in Nematode management.
Chemical management of Phyto Nematodes
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- DD mixture
- EDB ( Ethylene DiBromide)
- MBr (Methyl Bromide)
- Toluene 1,3 dichloro propene
- Nemadgon or DBCP – DibromoDichloro Propane (Banned)
Non Fumigants spraying:
- Metham sodium
Biological control of Plant Parasitic Nematodes:
There are some pathogenic fungi like Paecelomyceslilacinus and a bacteria Pastureiapenetrans that kills or arrests the growth of plant parasitic Nematodes.