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Root knot nematodes on tomato n the state of Meghalaya, India

A ProMED-mail post
http://www.promedmail.org
ProMED-mail is a program of the
International Society for Infectious Diseases
http://www.isid.org

Date: Tue 7 Jan 2025
Source: HortiDaily [summ. Mod.DHA, edited]
https://www.hortidaily.com/article/9692570/more-eco-friendly-methods-to-destroy-malaysian-%20pest/

Root knot nematodes have been causing significant damage to tomatoes in the state of Meghalaya. Tomato crops have been severely affected, reducing yields by up to 30%. Monocropping practices involving cabbage and cauliflower have further aggravated the problem.

The Central Agricultural University (CAU) Imphal and the Indian Agricultural Research Institute (IARI) have conducted trials to test biological agents to control the nematodes. Lemongrass oil (0.2%) achieved a nematode juvenile mortality rate of more than 99% within 48 hours and reduced root penetration by over 95%. Biocontrol agents like _Pochonia chlamydosporia_ and _Purpuricillium lilacinum_ significantly reduced nematode egg hatching, while _Trichoderma harzianum_ improved plant growth and resistance.

--
Communicated by:
ProMED

[Root knot nematodes (_Meloidogyne_ species) attack a wide range of plants and cause significant economic losses in many vegetable and fruit crops. The genus contains around 70 species and is found worldwide in tropical and subtropical regions in many types of soil. Symptoms may include stunting, wilting and leaf chlorosis; large galls are formed throughout the root system affecting plant vigour and even killing the host. Affected plants may show increased sensitivity to other bacterial or fungal pathogens.

Root knot and many other nematodes can persist in the soil for many years and are spread by plant material, soil and mechanical means (for example contaminated equipment). Once they have been established in an area, it is difficult to control them. Disease management is generally aimed at keeping nematode levels below economic thresholds. An integrated approach is required, including phytosanitation (exclusion), cultural measures (such as long crop rotation with non-host species), nematicides and use of resistant crop varieties, if available.

Tomato (_Solanum lycopersicum_) is a major host for _M. enterolobii_ which has been found previously in India in other crops (e.g. ProMED posts 20180305.5665346, 20180412.5743115) and may be the species referred to above. This species is polyphagous and, although its precise host range is still unknown, has been found on many economically important crops including potato, coffee, guava, soybean, melons and a range of vegetables. While it originates in subtropical areas, it also poses a serious threat to glasshouse crops in cooler regions. It is considered an emerging and particularly aggressive pathogen with increased virulence against crop varieties resistant to other root knot nematodes (e.g. ProMED post 20080912.2846).

Antagonistic fungi in the genus _Trichoderma_ have been shown to be effective as biocontrol organisms to suppress various fungal pathogens (e.g. ProMED posts 20160317.4102576, 20151109.3779551, 20130805.1864259), as well as some nematodes including _Meloidogyne_ spp. (see links below).

_Pochonia chlamydosporia_, now reclassified as _Metacordyceps chlamydosporia_, is a nematophagous fungus that can parasitise root-knot nematodes and promote plant growth. _Purpureocillium lilacinum_ is a species of filamentous fungus which has been isolated from a wide range of habitats, including cultivated and uncultivated soils.

Pictures
Root knot (_Meloidogyne_ spp.) damage on different hosts:
https://image.slidesharecdn.com/rootknotdiseaseoftomato-161217114101/95/root-knot-disease-of-tomato-5-1024.jpg (tomato),
https://www.infonet-biovision.org/res/res/files/2171.280x185.clip.jpeg,
https://www.agric.wa.gov.au/sites/gateway/files/Carrots%20RKN%20037.jpg,
https://3.bp.blogspot.com/-h59Eoc8aUe8/Udm7sUcUwKI/AAAAAAAACeE/KM-IjOh1i0c/s1600/P1160726.JPG,
https://www.mississippi-crops.com/wp-content/uploads/2016/01/DSC_1047.jpg,
https://guilford.ces.ncsu.edu/wp-content/uploads/2017/05/sweet-potatoes.jpg and
https://plantpathology.ces.ncsu.edu/wp-content/uploads/2017/05/Menterolobii_sweetpotato.jpg
_Meloidogyne_ photo gallery:
https://www.insectimages.org/browse/subthumb.cfm?sub=7001

Links
Information on _M. enterolobii_:
https://gd.eppo.int/taxon/MELGMY,
https://entnemdept.ufl.edu/Creatures/NEMATODE/Meloidogyne_enterolobii_Guava_or_pacara_earpod_root_knot_nematode.htm and
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2618283/
Information on root knot nematode diseases & pathogens:
https://www.agric.wa.gov.au/capsicums-and-chillies/root-knot-nematodes-western-australia,
https://plantdiseasehandbook.tamu.edu/problems-treatments/problems-affecting-multiple-crops/root-knot-nematodes/ and
https://extension.umd.edu/resource/root-knot-nematodes-vegetables
Genus _Meloidogyne_ taxonomy and species list:
https://www.uniprot.org/taxonomy/189290
Fungal taxonomy via:
https://indexfungorum.org/Names/Names.asp
Information on _Trichoderma_ spp. and use for biocontrol:
https://biocontrol.entomology.cornell.edu/pathogens/trichoderma.php,
https://doi.org/10.1007/s00253-010-2632-1 and
http://benthamopen.com/contents/pdf/TOMYCJ/TOMYCJ-8-71.pdf
_Trichoderma_ for nematode control:
https://doi.org/10.1038/s41598-023-33669-z,
https://doi.org/10.5772/intechopen.99218 and
https://doi.org/10.3389/fmicb.2023.1160551 (review)
- Mod.DHA

ProMED map:
India: https://promedmail.org/promed-post?place=8721366,142]