During a survey of cultivated fields 24 genera and 31 species of plants infested with root-knot nematode were collected from different parts of Pakistan. Anethum graveolens, Coriondrum sativum, Cucumis melo, Daucus carota, Ficus elatica, Lactuca sativa were found to be new hosts of Meloidogyne incognita not hitherto recorded with Cucurbita foetidissima, Cucumis melo, Prosopis juliflora, Ricinus communis, Solanum nigrum as new host records of M. javanica from Pakistan.
Soil amendment with different organic materials such as dry leaf powder of Annona squamosa, Justicia adhatoda, Catharanthus roseus, Datura fastuosa, Azadirachta indica, Eucalyptus sp., Calotropis procera, Prosopis cinerarea, P. glandulosa, P. juliflora; chopped fresh leaves of neem, castor, datura, bakain, eucalyptus, nerium, calotropis, neem seed powder, sugarcane bagasse, and dry powder of Jolyna laminarioides, Stoechospermum marginatum, Metinothamnus somalensis and Cystoseira trinodis showed effective control of M. javanica root-knot disease on tomato, brinjal, okra, mungbean, cauliflower, lettuce, pea, chickpea and sponge gourd with improvement in different growth parameters. Plant growth increased as the dosage of organic amendment increased whereas at higher dosages,organic amendments showed phytotoxic effects with reduction in growth parameters and or wilting. Application of different organic amendments reduced nodulation on mungbean used as test plant.
Use of neem, cotton, mustard, sesame and castor oil-cakes also significantly inhibited the development of root galls on tomato, brinjal, mungbean, sponge gourd and okra with subsequent increase in plant growth. Mustard cake @ 1.0% w/w showed phytotoxic effects. Neem cake was found to be most efficacious against root-knot nematode and was at par with chemical nematicides. Efficacy of organic amendments in the control of root-knot nematodes gradually increased as the period of decomposition increased upto 15-20 days which declined there after.
Water extracts of leaves of neem, datura, calotropis, castor, mustard oil cakes, neem seed powder and S. marginatum seaweed were found highly toxic to M. javanica root-knot nematode. The toxicity of extracts increased with an increase in concentration of the extract. Bare-root dip treatment of tomato and brinjal seedlings in extracts of neem seed powder, neem cake, mustard cake, castor cake and neem leaves also provided protection against M. javanica root-knot nematode with increase in plant growth. Development of root galls decreased with an increase in concentration of the extracts and the duration of dip treatment. Extracts of neem seed powder and neem cake when used as seed treatment also suppressed M. javanica root-knot disease in sponge gourd.
Whereas aldicarb as compared to neem derivatives showed greater reduction on brinjal, tomato and okra in the number of root-knot galls/plant, however, improvement in plant growth was found greater in plants grown in neem cake amended soil. A 15 days pre-plant treatment with neem derivatives greatly suppressed root-knot development as compared to plant-treatment while aldicarb and carbofuran were found more efficacious in post-plant treatment as compared to pre-plant treatments.
Use of microbial antagonists viz., Paecilomyces lilacinus, Bradyrhizobium japonicum and Verticillium chamydosporium with organic amendments or chemical fertilizers significantly increased their efficacy in the control of root-knot ,nematodes and also improved plant growth. P. lilacinus not only enhanced the efficacy of organic amendments but also stimulated root nodulation in mungbean.
Mixed-cropping of brinjal and tomato plants with marigold (Tagetes erecta) also significantly suppressed M. javanica root-knot disease with subsequent increase in growth of plants and yield.
Crude extracts of 87 different plant species belonging to 46 families and 12 seaweeds were tested for their nematicidal activity in vitro. Most of the plant species caused significant mortality of larvae of M. javanica root-knot nematode. Nematode mortality increased with an increase in the exposure time. Annona squamosa, Cocculus pendulus, Datura fasrtusoa, latex of Euphorbia spp., Solanum Surattense and seaweed species viz., Cyrtoseira trinodis, Jolyna laminarioides and Stoechospermum marginatum showed complete mortality of M. javanica larvae after 72 hours.
Fractions from extracts of plants viz., D. fastosa, S. surattense and seaweeds viz., J. laminrioides and S. marginatum which showed strong nematicidal activity of M. javanica larvae were found to .contain a mixture of terpenoids. Of the 6 tropane alkaloids viz., (3a-tigloxytropane, apoatropine, tropine, hyoscyamine, (-)-6β tigloyloxy tropane and scopolamine isolated from D. fastuosa, apoatropine and hyoscyamine were found inactive while the remaining compounds showed significant nematicidal activity.