Poor hosts of root knot nematodes and their application as rotation crops in okra production

Kimenju JW, Mweke AN, Mutitu EW, Mutua GK. "Poor hosts of root knot nematodes and their application as rotation crops in okra production.". 2010.


The response of 21 different crop plants to a mixed population of root-knot nematodes, Meloidogyne javanica and M. incognita, and their potential for use as nematode suppressive crops was evaluated in greenhouse and field experiments. Second stage juveniles (J2) were determined under each crop after extracting them from 200 cm3 soil. The reaction of the crops to root knot nematodes was classified as resistant, moderate or susceptible. Crops classified as resistant included maize, sorghum, millet, guwar and pigeonpea, which had galling indices ranging from 1.4-3.6. Cowpea ‘K80’ was rated as moderately resistant with a galling index of 4, while susceptible crops were greegram, cowpea ‘KKI’ and okra (control), with galling indices ranging from 5.6-7.4. Four crops (sweetcorn, babycorn, maize cv. Pioneer (Ph3253) and guwar) were selected from greenhouse tests for the field trials. The selection was based on their poor host status to root knot nematodes as well as relative acceptability to growers. These crops were then incorporated into a rotation programme with okra. Initial and final nematode (J2) numbers in the field was determined before planting and at the end of the season, respectively. Among the crops tested, the highest (44%) decline in nematode populations was recorded in plots under guwar and sweetcorn while the least (21%) was recorded under babycorn. In contrast, 441% increase in nematode numbers was recorded under continuous crop of okra. Okra was then sown in the plots previously grown with the selected nematode suppressive crops and the population of nematodes determined mid-season and at the end of the season. The severity of root knot nematodes on a crop of okra that followed sweetcorn was 3.3 compared to 8.6 in the control which as continuously under okra. This underscores the potential of rotating highly susceptible crops with poor hosts in the management of root knot nematodes

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