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Root knot nematodes found on onion (by Dr. Hajihassani)

Onion fields infested with root knot nematodes (RKN) were found in the Vidalia area. As can be seen in the picture (Photo: Aubrey Shirley), typical symptoms of RKN on above-ground parts of plants can involve patchy stunting, poor growth and yellowing of leaves. These symptoms are rather similar to nutrient deficiency. Premature wilting of plants can be seen when the nematode population in soil is high. Characteristic damage symptoms by RKN are  galled or swelled roots however the gall produced by these nematodes on onion are small compered to those produced on other vegetable crops. Therefore attention need to be taken when observing roots for galls. This group of nematodes have a wide host range and hence the crop chosen for rotation with onion should be selected  carefully in infested fields. The most common and effective management of RKN on onion is pre-fumigation of soils particularly the plant beds and also post-plant applications of nematicides. Taking soil samples and sending them to a nematode diagnostic laboratory is always the best way to prevent any damage caused by this nematode pests.