Cucumber (Cucumis sativus L.) is a high nutritious and mineral-rich vegetable, which occupies a prominent place as a salad and vegeta-ble. It is being used in many ways in the daily diet of humans and widely cultivated worldwide. The decrease of agricultural land, ad-verse environmental conditions and continuous increase of popula-tion, the demand of nutritious food is a matter of great concern to the world. Protected cultivation is a very effective tool to solve this problem because in this cultivation the productivity of crops is very high as compared to open field conditions. High value crops suc-cessfully grown in protected cultivation, specially vegetables (cu-cumber, tomato, Capsicum etc.) which are highly susceptible to the numerous pests and pathogens, including phyto-parasitic nema-todes (specially root-knot nematode, Meloidogyne spp.). With this view, present trial was taken to estimate the avoidable losses caused by Meloidogyne incognita infecting cucumber in poly-house situated on farmer’s field with the application of phorate at 2 kg a.i. ha-1 over check. Results exhibited that application of chemical treatment significantly reduced number of galls per 5 g roots, egg masses per 5 g roots, eggs & juveniles per egg mass and final nema-tode population 79.03, 81.10, 30.91 and 56.54%, respectively. Avoidable yield losses were recorded to the tune of 66.84% on cu-cumber by M. incognita in poly-house.