In the backdrop of reports of rising decline of orchard productivity in Tamil Nadu, farmers have been alerted to check randomly polybags by removing the soil medium and observing roots for any knots or swellings, before they make bulk purchases from nurseries.

This will avoid entry of nematodes into orchards through the plant materials, which once established, become difficult to control, an advisory by Tamil Nadu Agricultural University (TNAU) said today.

Of late, there has been increasing episodes of decline in orchards in the state and has been attributed to fungal wilt often predisposed by root knot nematodes.

The incidence occurs at the nursery stage, where the planting materials such as ground layers, rooted cuttings and grafts are themselves infested with root knot nematodes.

The symptoms are sometimes seen as marginal necrosis in leaves and small knots/galls (roundish swellings) on roots.

Such infested materials once planted in fields will start deteriorating the plants after one to two years by which time it would be too late to retrieve the plants.

Nematodes pave way for entry of fungi through the wounds caused by their feeding, which further aggravates the situation by way of causing wilt disease in fruit orchards.