Management of Phytophthora disease in black pepper nursery

Abstract

Phytophthora rot is the serious disease of black pepper nursery. An investigation was carried out to isolate and select the efficient antagonists from black pepper nurseries and use them alone or in combination with fungicides in the integrated management of the disease. The experiment was laid out at CCRP farm at College of Horticulture, Vellanikkara, The pathogen causing the disease was isolated and identified as Phytophthora capslcl Leonian emend A. Alizadeh and P.H.Tsao based on the cultural and morphological characters. Quantitative estimation of rhizosphere microflora from different pepper nurseries yielded more soil bacteria followed by fungi and actinornycetes. All the 22 fungi, five out of 20 bacteria and none of the actinomycetes tested were antagonistic to P. capsici. Among the fungal isolates, 13 isolates including standard culture of T. harzianum recorded cent per cent inhibition of P. capsici. Further, selection of the efficient isolates was carried out based on the antagonistic index (AI). The isolates 22 F and 34 F recorded an AI of3000 and 1500 respectively and these were identified as Trichoderma longibrachiatum and Trichoderma viride. The standard culture of T harzianum also recorded an AI of 1500. The three antagonists were found parasitic on Picapsici as evidenced by excessive coiling, penetration and disintegration of the hyphae. The fungicides viz., Bordeaux mixture, Kocide, Captaf and Kavach were incompatible with the three antagonists, while, lndofil M-45, Ridomil I\.1Z, Akomin and Anthracol were compatible. Fytolan showed partial compatibility with Tviride and 1~ harzianum but incompatible with T. longibrachiatum. Among the eight insecticides tested, Phorate and Carbofuran showed compatibility with the antagonists, whereas Monocrotophos, Quinalphos, Endosulfan, Dimethoate, Cypennethrin and higher concentration of Chlorpyrlphos were incompatible. In general, fertilizers like Urea, Rajphos, Ammonium sulphate and Muriate of potash (MoP) were compatible with antagonists, while, Factomphos and higher concentration of Urea did not support good growth. 149 Bordeaux mixture, Fytolan, Kocide, Indofil M-45, Ridomil MZ and Captafat all concentrations and higher concentration of Akomin-40 and Anthracol were inhibitory to P. capsici. The insecticides Phorate, Carbofuran and Chlorpyriphos showed comparatively good inhibitory effect against the pathogen but complete inhibition of pathogen was noticed with Monocrotophos, Endosulfan, Quinalphos, Dimethoate and Cypermethrin. The fertilizers viz., urea, MoP, Rajphos supported growth of the pathogen while, Factomphos and ammonium sulphate exerted an inhibitory effect. Solarization of potting mixture resulted in the build up of soil temperature and the build up was more in the upper layer of soil. Solarization of potting mixture and application of biocontrol agents had a positive effect in increasing the sprouting and reducing the pre-sprouting mortality of cuttings and is comparable to plants raised as per PoP. Observations on the incidence and severity of Phytophthora rot in black pepper showed that in general soil solarization, application of antagonists and spraying of Ridomil MZ had a favourable effect in checking the disease and the effect is almost similar to that of disease management as per PoP. A variation in the population of soil microfIora in different treatments was o~~rved. Thy cuttings raised in solarized potting mixture incorporated with native antagonists had a significant effect in increasing the height and number of leaves.