Plant parasitic nematodes are obligate parasites feeding on roots of crop plants. Globally plant parasitic nematodes accounts for an annual yield loss of 173 billion dollars (Elling, 2013). Among the plant parasitic nematodes, Meloidogyne spp. is one of the most damaging nematode genera which is widely distributed and infecting important agricultural and horticultural crops. Their polyphagus nature and their ability to infect a variety of important crops makes them one of the notorious crop pests. Globally they are responsible for billions of yield loss every year. Their problem is much more severe in crops like capsicum, tomato, gerbera etc. which are grown under protected condition for commercial purpose leading to complete closure of cultivation.
There are more than 100 reported species of Meloidogyne globally. Among them, M. incognita, M.javanica, M. arenaria, and M.hapla are considered as major root knot nematode species infecting most of the cultivated crops. The other root knot nematode species like M.graminicola, M.exigua, M.chitwoodi, M.fallax, M.naasi, M.minor, M.enterolobii etc. are considered as minor root knot nematode species with restricted distribution.
Nowadays, these minor root knot nematode species are spreading quickly and emerging as major problems in crop production. Among these minor root knot nematodes, M.enterolobii is now spreading quickly to different cultivated crops and new areas where it was not existing earlier. Like most of the other root knot nematodes, M.enterolobii is also polyphagus and can infect vegetable crops like tomato, okra, capsicum, sweet potato, ornamentals and fruit crops like guava, melon, fig etc.. It was first reported on a perennial, Pacara earpod tree from Hainan island, China (Baojun and Eisenback, 1983). Later on, this species has been recorded from Africa (Burkina Faso, Ivory Coast, Malawi, Senegal, South Africa, Togo), Asia (China, Vietnam), North America (USA, state of Florida) and Mexico, Central America and the Caribbean (Cuba, Guatemala, Martinique, Guadeloupe, Puerto Rico, Trinidad and Tobago) and South America (Brazil, Venezuela)(EPPO 2016). This nematode was placed in EPPO A2 list by considering the risk of its introduction and dissemination in the European region (Freitas et al., 2017).
M.enterolobii is posing a serious threat to guava (Psidium guajava) cultivation throughout the world. More recently it was reported from India on guava orchards of Tamil nadu where trees were declining showing yellowing and stunted growth (Poornima, et al., 2016). It was also identified from guava orchards of Andhra Pradesh and Telangana, India. This nematode causes severe root galling there by reducing the nutrient uptake ability of the plant.
Symptoms induced by this nematode include yellowing and stunting, reduced fruit size, drying of branches, shredding of leaves and reduced yields. Severe infestation by this nematode leads to heavy root galling which succumbs the tree to decline and death. Synergistic effect will be seen when this nematode is associated with other fungal pathogens like Fusarium solani, Verticillium spp., Pythium spp and can causes death of guava trees within few months (Gomes et al., 2010).
This nematode is spreading to new areas through infected guava saplings. Management of this nematode is a challenge because of its polyphagus nature and ability to survive on weed hosts. Even the Mi gene which confers natural resistance to root knot nematodes proved ineffective to M. enterolobii.
Some of management options to prevent nematode entry into new orchards include