Root-knot nematode emerging as major threat to guava nursery industry

Shailendra Rajan, Director (CISH) apprising the magnitude of the problem conveyed that extensive/intensive surveys undertaken by Principal scientist Dr. R.M. Khan have brought to fore that Private and govt. nurseries located especially in Lucknow, Badaun and Farrukhabad regions have been principally found the source of inoculums and subsequent cause of infestation build up first in nurseries itself followed by its spread and subsequent infestation in the newly established orchards in the areas of Rajasthan where guava cultivation has captured significant acreage.

Symptoms of infestation appear in form of swelling of roots which goes unnoticed and eventually turn into elongated swelling giving an appearance of beads. Severe infestation leads to formation of galls of varying shape and size ranging from oval, globose to spherical. Root infestation and formation of galls restricts the root growth which is reflected in form of poor plant growth with lesser number of branches having leaves of smaller size. Severely infested grafts succumb to mortality even in poly bags/beds. Such grafts in poly bags when uprooted exhibit blackened and rotten roots due to subsequent infection of fungi. Grafts having smaller size galls become the potential source of spread of pest infestation in far and wider areas. Infested plant when introduced in the newer areas carries the infestation along. Infested plants initially depending upon the infestation level may exhibit normal growth initially for a period of 1 to 2 year. However, gradually the population increases resulting in poor stand of plants having smaller size, lesser number of leaves. Plants having infestation of nematodes becomes vulnerable to fungal infection and starts exhibiting rotting of the whole root system resulting in complete mortality of even grown up established plants on the orchards. The craze for a higher profit margin, poor understanding of the pests and disease scenario and non-adoption of good nursery maintenance practices (GNMP) has led to the emergence of root-knot nematode a soil-based pest responsible for ruining even the grown-up guava orchards as one of the important factors in the arena of pest complex.