Citrus Nematode and their Control

Citrus Nematode (Tylenchulus semipenetrans) : Infestation of nematodes is one of the main factors responsible for slow decline of citrus. Damage caused by a citrus nematode infestation depends on the age and vigor of the tree, density of the nematode population, and susceptibility of the rootstock. Mature trees can tolerate a considerable number of these nematodes before showing lack of vigor and decline symptoms. In heavily infested sites, young trees may be stunted or fruit production may be reduced on bearing trees that have susceptible rootstocks. The damage is greater when trees are predisposed by other factors such as Phytophthora root rot and water stress.

Symptoms: Symptoms of nematode damage above the ground are lack of vigor, twig dieback, decline in growth, and reduced fruit size and yield. Nematode infestations may occur without inducing any aboveground symptoms. Under ground symptoms of citrus nematode infestation include poor growth of feeder roots and soil adhering to roots giving them a dirty appearance.

Control : Good sanitation practices are essential to avoid nematode infestations. Use certified nematode-free material for planting. Rotation with annual crops for 1 to 3 years before replanting citrus helps to reduce citrus nematode populations. Using a resistant rootstock is recommended whether or not nematodes are present. Trifoliate orange is known to be tolerant to citrus nematode. Soil application of Neem cake and chemicals like Temic 10G (4 kg a.i./ha) are used successfully to control the nematodes. Intercropping of Marigold has repellent action and reduces the population of nematodes in citrus.