Impact of Plant Oils, Biocontrol Agents and Oxamyl on Galling and Reproduction of Meloidogyne incognita Infecting Pepper Cultivars

Abstract

A greenhouse experiment was carried out to evaluate the nematicidal activity of two biopesticides (Nema k & Nema clean), two plant oils (Inula viscosa & Azadirachata indica) and two entomopathogenic nematodes, (EPNs) i.e. Steinernema feltiae and Heterorhabditis bacteriophora) compared to chemical nematicide, oxamyl on root-knot nematode, Meloidogyne incognita infecting three cultivars of pepper (Capsicum annuum L.). Biopesticides were applied at the rate of 0.4 ml /plant whereas, the plant oils were tested at the concentration of 400 µL\plant. EPNs were accomplished simultaneously with inoculation of M. incognita as a liquid suspension of alive infective juveniles (IJs) at rate of 5000 IJs/plant in sandy soil. Oxamyl at recommended rate of 0.2 ml/plant. Control treatments received only water and M. incognita at rate of 1000 IJs/plant. Two months after application, galling (as indicated by number of galls/plant) and reproduction (as indicated by number of egg masses /plant) as well as damage (as indicated by fresh and dry weight of areal parts) were assessed. Data showed that, oxamyl treatment surpassed all other treatments in minifying galling and reproduction of M. incognita in sandy soil. From all tested materials, oxamyl, biopesticides and EPNs were the most effective in suppressing root galling and number of egg masses of M. incognita infecting pepper cultivars. On contrarily, plant oils were the least effective ones. Maximum percentages of reduction were recorded on cultivar 1515 when plants were treated with oxamyl (92.17&79.47%) followed by S. feltiae (90.21& 70.19%) and biopesticide, Nema clean (89.34 & 68.86%). On the other hand, statistically oxamyl was the first tested material in declining number of infective juveniles of M. incognita on three peppers cultivars. The curative application with oxamyl and Nema clean (Serratia marcescens) achieved the highest percentage increase in fresh (47.11 & 41.33) and dry (16.59 & 16.67) shoot weight, respectively. Next to oxamyl, entomopathogenic nematodes (S. feltiae) showed better performance in diminishing number of galls and egg masses of M. incognita infecting pepper cv. Lama than did on cv. Rima. However, the maximum percentages of increase in fresh and dry shoot weights of pepper were recorded on cv. Lama in pots receiving oxamyl (11.48 & 32.70%) and Nema clean (9.47& 27.50%).