Sukumara Varma, ASree Kumari, P KKAU2020-11-232020-11-231995170872https://krishikosh.egranth.ac.in/handle/1/5810155549MScSymptomatology and etiology of little leaf disease of pepper (piper nigrum L.) was conducted at the department of plant pathology, College of Horticulture, Vellanikkara, Thrissur and at pulppally in Wayanad district during 1992-94. Based on the external symptoms of the disease a disease scoring chart (0 to 4) was perfected. The diseased plants had shorter main root and less number of feeder roots. Brown discoloration was noticed on diseased roots. Internodal length as reduced which give a bushy appearance to the plant. Leaves were distorted, downwardly curved, chlorotic, brittle with wire-net type vein lets. Enen though the size and shape were normal, the number of flowers per spike decreased and the aborted flowers increased. Proper maturity was obtained by very few berries. Disease was observed to attach all age group of plants, but the intensity increased with age. Variety karimunda was highly susceptible and punniyur-1 was observed to be tolerant though the disease attacked Arakkulam munda, Aimpiriyan and Vellananamban with lesser degree than karimunda. Application of zinc did not inhibit the symptoms. When 0.2% Dienes stain was used for the phloem portion of the roots, nodes and petioles of the diseased and healthy plants, only diseased plant parts stained blue indicating the presence of mycoplasma like organisms in them. Disease could not be transmitted by sap or dodder. It could be transmitted by cuttings and by wedge grafting using diseased root stock and healthy scion not vice versa. Transmission studies with insects Austroagallia sp. Manderan beta Owarokowska aand Liothrips Karnyi were not successful. Applications of oxytetracycline hydrochloride (OTC) by drenching, spraying, dipping and wick feeding were effective at concentrations more than 500 ppm for remission of disease symptoms. OTC at 250 ppm was not effective. Above 750 ppm, the treatment caused phytotoxicity. Among methods, wicks feeding was found to be the best, which prevented reappearance of symptom even after two years where as in all the other methods, the symptom remission lasted for less than 6 months. Yield was observed to be reduced with an increase in disease intensity. The study revealed the symptomatology of little leaf disease of black pepper and resulted in the identification of etiology as mycoplasma like organism.EnglishThesis