Chemical control of tobacco root-knot nematode (Meloidogyne incognita)
Root-knot nematode ( Meloidogyne spp.) is one of the major pathogens of tobacco production in almost all tobacco-growing areas. Losses from root-knot are heavy; in combination with other pathogens the disease can be disastrous every year. Stunting and yellowing characterize plants affected by root-knot nematode. The most distinctive symptoms of root-knot are the galls on the roots. In this study in 2007 the effect of nematicides Rugby 10G (Cadusafos) and Nemacure 10G (Fenamiphos) at concentrations 40, 60 and 80 Kg/ha was investigated against tobacco root-knot nematode ( M. incognita ) and each nematicide was applied at three different times: before, synchronized and after inoculation with the pathogen at the Tirtash Research and Education Center. The pots (except control), were inoculated with 3000 larvae (J2) and eggs in each Kg pot soil (sandy-loamy pasteurized). Infected root samples were collected from tobacco fields in the Jafarabad area of Golestan province in the north of Iran. Single egg masses were inoculated on tobacco cultivar Virginia (Coker 347). The species of nematode was determined by using perineal pattern obtained from adult females, were mounted in glycerin and examined by light microscopy. Experimental design was complete randomized design with four replications. After seven reapings and at the end of the growing season, the effectiveness of the nematicides was assessed on the basis of number of nematodes in root and soil, gall index, number of egg masses, average number of eggs per egg mass, and reproduction factors (Rf). The growth factors, fresh and dry weight and number of leaves, height of plant, fresh and dry weight of root and length of root, sugar and nicotine percentage, income and average price were measured and data were analyzed with SAS program. Morphological observations based on female perineal pattern matched typical traits of M. incognita . The response of the M. incognita to differential hosts was evaluated in a glasshouse at 25 ± 3 °C and was identified as race 2 of M. incognita . The results showed that treatments are significantly different (p<0.1) from the control (check), but the fresh weight and number of leaves, plant height of treatments were not significantly different. It was also revealed that the treatment Nemacure 80 Kg/ha (before inoculation) caused an 85.57% reduction in the population of eggs and (J2) respectively while the control treatment had an increase in nematode population of eggs and (J2). On the basis of overall results, concentrations 80 Kg/ha had the best efficiency in controlling the disease.