PATHOGEN: -Pratylenchus species
Nematode is a widely recognized group of a distinct phylum Nematoda or Nemata under superphylum Ecdysozoa (all moulting animal group).
Over 400 host plant species including potato, peanut, Paddy, Tomatoes, Brinjal, Cucurbits and fruit Plants Guava, Pomegranate etc.
Typical root symptoms indicating nematode attack are root knots or galls, root lesions, excessive root branching, injured root tips and stunted root systems
Symptoms of lesion nematode disease (as with most nematode-induced diseases) often go unrecognized initially because the nematodes are microscopic pathogens of belowground plant parts (mainly roots), and the aboveground symptoms are often general symptoms of plant root stress.
Agriculture damage is the caused by plant parasitize nematodes that live in the soil. Since nematodes parasitize the roots of plants, they cause agriculture damage such as poor growth and withering of plants.
Agriculture Damage caused by nematodes has become a major problem worldwide.
Many types of nematodes live in the soil, but plant parasites such as Root-Knot nematodes, Negusare Nematodes, and Cyst nematodes are particularly problematic in agriculture.
Various crops are parasitized, and if they are parasitized at high density, the crop will eventually wither rather than reduce the harvest, therefore, it is very important to keepnematode densities low and controlled throughout the year.
Crop rotations to non host crops also offer limited opportunities to manage lesion nematode field populations since most Pratylenchus species have wide host ranges including both dicots and monocots. If the species of Pratylenchus is accurately diagnosed, and a suitable economic nonhost can be grown, rotations offer some promise as a management tactic. There are suggestions that microbial antagonists of lesion nematodes such as soil fungi can reduce population levels, but this has not been proven to be effective in production agriculture
Cultural practices are the most effective and economical means of managing insect-pests and dis-ease including nematode problems. Two to three summer ploughings (20 cm deep) during the months of May to June at the interval of 15 days expose nematodes, weeds, pathogen propagules and hibernating stages of insect-pests to sunrays. Intercropping with antagonistic plants like marigold
Crop rotation with resistant varieties or non- host crops like mustard, sesame, maize, wheat, etc. is useful in bringing down soil nematode populations below the damage threshold level.
Application of organic manure, farmyard manures (FYM), at 18–20 t/ha reduces nematode population through their multiple actions: releasing of toxic substances, enhancing of crop tolerance and encouraging of soil microbial antagonists either alone or simultaneously.
The best way to manage lesion nematodes is to prevent their introduction into a field. Choosing an uninfested field site or choosing a nonhost rotation crop are two ways to avoid problems with lesion nematodes. Once lesion nematodes infest a field, it is highly unlikely that they can be eradicated. Inoculum levels can be reduced by moldboard plowing (turning over the soil layer) to expose infected roots to the elements. Planting stock should be monitored and certified to be free of lesion nematode infestation.
Since many weeds are hosts for lesion nematodes, poor weed control will increase lesion nematode field populations and, most likely, increase crop damage. Destruction and removal of infested perennial crops, followed by soil fumigation, are drastic, but effective tactics to reduce subsequent lesion nematode-related damage.
Plant resistance plays an important role in the integrated management of nematodes diseases. However, availability of resistant varieties of vegetable crops is very few in number, and many of them are not acceptable to the farmers for their suitability.
Chemical control with the application of nematicide’s is one of the most effective means of nematode management. However, most of the effective nematicides have been withdrawn from the world market. At present, a few insecticides having nematocidal property are available to the farmers, but because of their high doses required to man-age nematode, they become cost-ineffective and leave high pesticide residues to the harvested crops. The application of nematicides through bare-root dip treatment, seed treatment and nursery bed treatment has been proven to be effective to pro-tact the young seedlings from nematode attack.
Nursery Bed Treatment
In most of the cases, the infection is carried through infested seedlings from nursery bed. The damage caused by nematodes to the root system of ten-der seedlings is more harmful than to older plants. The application of nematicides to nursery bed helps to raise nematode-free seedlings. Moreover, it reduces the dose of nematicides and cost substantially. The soil application of carbofuran at 0.3 g i.e./m 2 is sufﬁcient for producing nematode-free seedlings of many trans-planted vegetable crops. The treatment of nursery bed with sebuphos or carbofuran or benfurocarb at 0.3 or 0.6 g i.e./m 2 at the time of sowing reduces the infestation of nematode
Root Dip Treatment
The seedlings of many transplanted vegetable crops can be dipped in systemic nematicides like oxamyl, prophos and dimethoate at 500–1000 ppm for 6 h to denematize the roots. The seedlings of transplanted vegetables like brinjal, tomato, chilli and planting materials of pointed gourd treated with carbosulfan (Marshal 25EC) at 500 ppm for 6 h provided effective control against nematode.
The practice of seed soaking and seed dressing is an important prophylactic measure which gives adequate initial protection to the young seedlings of tomato, brinjal, okra, chilli, etc. The most commonly used systemic nematicides, viz. fenamiphos, isofenphos, carbosulfan, etc.
Field application of carbofuran 3G at 2 kg i.e./ha in tomato, brinjal, chilli and okra reduce nematode population and increases yields.
Dimethoate, carbosulfan etc. can be adopted for providing better crop with early protection against nematode.
Paecilomyces lilacinus, Pochonia chlamydosporia, Trichoderma viride, Pseudomonas ﬂuorescens and Pasteuria penetrans, have been found effective and showed promising for managing nematode.