Outbreak of Leaf Miner and Root Knot Nematode-wilt Disease Complex on Cucumber- A New Threat under Protected Cultivation in District Gurugram Haryana

Abstract

Background: Crops are constantly exposed to various organisms feeding on above and belowground parts under both natural and protected conditions. As compare to open field, the warm and humid conditions besides abundant food under protected conditions provide a stable environment for pest and disease development either alone or together. However, the natural enemies i.e. predators, parasites and parasitoids that keep pests and pathogens under control naturally are not present under protected environment. For these possible reasons, pest and pathogens often develop in polyhouses more rapidly and with greater severity than open fields.Methods: A polyhouses study was carried out during last two months June and July in Patudi block of district Gurugram, Haryana where growers are facing failure of cucumber crop due to outbreak of insect pests- disease complexes on common host cucumber. On closer observation, symptoms of leaf miner as mining lines on leaves and galls or knots on roots the symptoms of root knot nematode were encountered. Further detailed lab based investigation were carried out on affected cucumber plant and root samples with the objective for isolation and identification of both pests and pathogens. For leaf miner morphological identification, the pattern of the feeding tunnel and the layer of the leaf being mined by leaf miner is one of the diagnostic key are useful to determine the species and instar of the leaf miner. However, Sieving and decantation method for nematode isolation and soil dilution method for fungal isolation were carried out and followed by morphological identification. Result: Two types of herbivore i.e. leaf miner Liriomyza trifolii (Burgess) on aerial parts while root knot nematode, Meloidogyne javanica and wilt causing fungus Fusarium oxysporum f. sp. cucumerinum were identified on the basis of their specific morphological characters. Galled roots of cucumber were affected by combined attack of vascular bundle feeders, root knot nematode, Meloidogyne javanica and wilt causing fungus Fusarium oxysporum f. sp. cucumerinum identified in both soil and root samples. This kind of field report on cucumber crop under protected cultivation has not been reported so far in which three types of pest and pathogens are feeding on the same host. Poly houses or ‘hot spots’ are selected for detailed investigation especially for growers’ friendly management in addition to interaction studies of upper and lower ground herbivores on cucumber crops.